Co-reporter:Gang Wu, Congjin Hu, Junyi Cui, Si-Chong Chen, and Yu-Zhong Wang
ACS Sustainable Chemistry & Engineering September 5, 2017 Volume 5(Issue 9) pp:7759-7759
Publication Date(Web):August 3, 2017
DOI:10.1021/acssuschemeng.7b01226
Despite considerable success in design and preparation of superhydrophobic particles, a facile and low-cost approach to develop multifunctional particles, especially microcapsules with the integrated performances of intrinsically long-lasting and highly stable superhydrophobicity and other passive/active functionalities, remains extremely challenging and is still in its infancy. Herein, we report a microcapsule (MC) with a micro/nano-hierarchical shell and a phase change material (PCM) core by a low-cost one-pot method. The resulting microcapsules (MCs) possess concurrent features of superhydrophobicity and thermal energy storage. Against thermal attack up to approximately 240 °C, the microstructure of MCs is nearly intact to avoid an obvious leakage of encapsulated PCM at high temperature, and meanwhile superhydrophobicity of MCs is enhanced unexpectedly to a static contact angle (CA) of 167.4 ± 0.3° and slide angle (SA) of 5 ± 0.5°. After conventional storage of 80 days, MCs still show a good superhydrophobicity with a nearly constant CA and slightly increasing SA. In addition, encapsulated PCM has high enthalpy up to 176 J/g, nearly unchanged Tm, Tom, and Tos, and negligible change (less than 0.1%) of normalized melting and solidified enthalpies over 100 melting/solidification cycles, indicating high latent heat, low effect of shell on thermal diffusion, and excellent durability during phase transition cycling, respectively. An isothermal stage at around 28 and 26 °C being close to human comfort temperature appears separately in heating-up and cooling-down processes of the epoxy matrix with embedded MCs, revealing a good temperature-regulated property of MCs. Accordingly, the MCs as a promising candidate with all-in-one features of superhydrophobicity, temperature-regulated properties, thermal-resistance, and durability would stimulate wide applications in self-cleaning/energy-saving smart buildings and facilities.Keywords: Microcapsules; Phase change materials; Self-cleaning; Superhydrophobicity; Thermal energy storage;
Co-reporter:Ming-Jun Chen;Ying-Jun Xu;Wen-Hui Rao;Jian-Qian Huang;Li Chen;Xiu-Li Wang
Industrial & Engineering Chemistry Research May 28, 2014 Volume 53(Issue 21) pp:8773-8783
Publication Date(Web):2017-2-22
DOI:10.1021/ie500691p
In this work, 2-carboxyethyl(phenyl)phosphinic acid melamine salt (CMA, phosphorus valence +1), melamine hypophosphite (MHPA, phosphorus valence +1), melamine phosphite (MPOA, phosphorus valence +3), and melamine pyrophosphate (MPyP, phosphorus valence +5) were respectively used as flame retardants for flexible polyurethane foam (FPUF), and fire performance as well as pyrolysis behaviors of FPUF were investigated systematically. CMA and MHPA were found to have better flame retardance than MPOA and MPyP for FPUF, which mainly played a role in the gas phase due to the release of many phosphorus-containing volatiles and melamine derivatives. The types of phosphorus-containing gaseous pyrolysis products of CMA were much more than that of MHPA due to the different chemical moieties surrounding the phosphorus atom, which made it have the highest flame-retardant efficiency for FPUF. Besides this, the possible thermal degradation mechanisms of CMA and MHPA were proposed.
Co-reporter:Juan Xue, Fei Song, Xue-Wu Yin, Ze-Lian Zhang, Ye Liu, Xiu-Li Wang, and Yu-Zhong Wang
ACS Sustainable Chemistry & Engineering May 1, 2017 Volume 5(Issue 5) pp:3721-3721
Publication Date(Web):April 5, 2017
DOI:10.1021/acssuschemeng.7b00341
The mesoporous structure and high exposure of the (001) facet are of great importance to the photocatalytic performance of TiO2. In this Letter, we report using cellulose nanocrystal (CNC) as a sacrificial template to develop mesoporous TiO2 with dominantly exposed (001) facets, for which CNC can provide confined space for the controlled crystal growth of TiO2 and create mesopores after being removed. Owing to the photoluminescence up-conversion, furthermore, carbon quantum dot (C-dot) is introduced to realize visible light catalytic property of TiO2. In particular, the TiO2/C-dot composite with an extremely low content of carbon dot exhibits high catalytic performance, for which the mechanism is discussed. These results indicate such biotemplating method offers the potential to develop more mesoporous nanomaterials with desirable structures.Keywords: Carbon quantum dot; Cellulose nanocrystal; Photocatalytic activity; TiO2;
Co-reporter:Ling Lin;Cong Deng;Gong-Peng Lin
Industrial & Engineering Chemistry Research June 3, 2015 Volume 54(Issue 21) pp:5643-5655
Publication Date(Web):2017-2-22
DOI:10.1021/acs.iecr.5b01177
Polycarbonate (PC) was incorporated into poly(lactic acid) (PLA) to prepare the high-PLA-content (≥66 wt %) PLA/PC blends with high impact strength and heat distortion temperature (HDT) via adding a compatibilizer to tailor the interfacial bonding and annealing to enhance the crystallization of PLA phase with the aid of an impact modifier. On the basis of the tensile test, scanning electron microscope, and transmission electron microscope observations, the change from the yielding behavior dominated by shear-yielding to a coexistence of shear-yielding and crazing should be the leading reason for the significant improvement of impact strength for the annealed PLA/PC blends. The increase of the ability to sustain the high local stress also played an important role in the improvement of impact strength. Meanwhile, the increase of HDT should be resulting from the formation of a rigid three-dimensional framework composed of rigid PC particles and PLA crystals formed in the PLA/PC blends.
Co-reporter:Qiu-Tong Li, Miao-Jie Jiang, Gang Wu, Li Chen, Si-Chong Chen, Yu-Xiao Cao, and Yu-Zhong Wang
ACS Applied Materials & Interfaces June 21, 2017 Volume 9(Issue 24) pp:20797-20797
Publication Date(Web):May 29, 2017
DOI:10.1021/acsami.7b01954
In the present work, we demonstrated the recyclability and precisely targeted reparability of amino functionalized multiwall carbon nanotubes–epoxy resin based on dynamic covalent Diels–Alder (DA) network (NH2–MWCNTs/DA-epoxy) by exploring the photothermal conversion of CNTs to trigger the reactions of dynamic chemical bonds. The covalent cross-linked networks of NH2–MWCNTs/DA-epoxy resin change their topology to linear polymer by thermally activated reverse Diels–Alder (r-DA) reactions at high temperatures, which endues the resin with almost 100% recyclability. The self-healing property of the epoxy resin was confirmed by the complete elimination of cracks after the reconstruction of DA network induced by heating or near-infrared (NIR) irradiation. For heat-triggered self-healing process, heat energy may also act on those uninjured parts of the resin and cause the dissociation of the whole DA network. Therefore, redundant r-DA and DA reactions, which have no contribution to self-healing, are also triggered during thermal treatment, resulting in not only a waste of energy but also the deformation of the sample under external force. Meanwhile, for the NIR-triggered self-healing process, the samples can maintain well their original shape without observable deformation after irradiation. The NIR-triggered healing process, which uses MWCNTs as the photothermal convertor, have very good regional controllability by simply tuning the MWCNTs content, the distance from NIR laser source to sample, and the laser power. The injured samples can be locally repaired with high precision and efficiency without an obvious influence on those uninjured parts.Keywords: Diels−Alder reaction; epoxy resin; photothermal conversion; recycle; self-healing;
Co-reporter:Ke Shang, Jun-Chi Yang, Zhi-Jie Cao, Wang Liao, Yu-Zhong Wang, and David A. Schiraldi
ACS Applied Materials & Interfaces July 12, 2017 Volume 9(Issue 27) pp:22985-22985
Publication Date(Web):June 16, 2017
DOI:10.1021/acsami.7b06096
Inorganc silica-based aerogels, the earliest and widely used aerogels, have poorer mechanical properties than their organic substitutes, which are flammable. In this study, a novel polymeric aerogel with high strength, inherent flame retardancy, and cost-effectiveness, which is based on poly(vinyl alcohol) (PVA) cross-linked with melamine–formaldehyde (MF), was prepared under aqueous condition with an ecofriendly freeze-drying and postcuring process. Combined with the additional rigid MF network and benifited from the resulting unique infrastructure of inter-cross-linked flexible PVA segments and rigid MF segments, PVA-based aerogels exibited a significantly decreased degradation rate and sharply decreased peak heat release rate (PHRR) in cone calorimeter tests (by as much as 83%) compared with neat PVA. The polymer aerogels have a limiting oxygen index (LOI) as high as 36.5% and V-0 rating in UL-94 test. Furthermore, the aerogel samples exposured to harsh temperatures maintain their dimensions (<10% change), original mechanical strength and fire safety. Therefore, this work provides a novel stragegy for preparing pure organic polymeric aerogel materials with high mechanical strength, dimensional stability, and fire safety.Keywords: aerogel; cross-linking; flame retardant; mechanical property; melamine−formaldehyde resin; poly(vinyl alcohol);
Co-reporter:Yu-Tao Wang, Hai-Bo Zhao, Kimberly Degracia, Lin-Xuan Han, Hua Sun, Mingze Sun, Yu-Zhong Wang, and David A. Schiraldi
ACS Applied Materials & Interfaces December 6, 2017 Volume 9(Issue 48) pp:42258-42258
Publication Date(Web):November 15, 2017
DOI:10.1021/acsami.7b14958
Biobased gelatins were used to improve the compressive properties and flammability of poly(vinyl alcohol)/montmorillonite (PVA/MMT) aerogels, fabricated using a simple and environmentally friendly freeze-drying method. Because of the excellent compatibility and strong interfacial adhesion between PVA and gelatin, the compressive moduli of aerogels were enhanced dramatically with the incorporation of gelatin. PVA/MMT/porcine-gelatin aerogels exhibit compressive modulus values as much as 12.4 MPa, nearly 300% that of the control PVA/MMT aerogel. The microstructure of the PVA/MMT/gelatin aerogels shows a three-dimensional co-continuous network. Combustion testing demonstrated that with the addition of gelatin, the self-extinguishing time of the aerogel was cut by half and the limiting-oxygen-index values increased to 28.5%. The peak heat-release rate, obtained from cone calorimetry, also decreased with the incorporation of gelatin. Thermogravimetric analysis demonstrated that the gelatins slowed the sharp decomposition of the PVA matrix polymer and increased the thermal stability of the aerogels at the major decomposition stage of the composite aerogels. These results indicate that as a green, biobased material, gelatin could simultaneously improve the mechanical properties and the properties of flame retardancy.Keywords: aerogel; clay; flammability; gelatin; mechanical properties; poly(vinyl alcohol);
Co-reporter:Liang-Ping Dong, Cong Deng, Yu-Zhong Wang
Polymer Degradation and Stability 2017 Volume 135() pp:130-139
Publication Date(Web):January 2017
DOI:10.1016/j.polymdegradstab.2016.12.002
Two kinds of polyamide charring agents, poly(piperazinyl malonamide) (PPMA) and poly(piperazinyl succinamide) (PPSA), were synthesized, and their only difference is that PPSA increases one methylene in the main chain compared with PPMA, which were confirmed via Fourier transform infrared spectroscopy (FTIR), Elemental analysis (EA), 1H nuclear magnetic resonance (1H-NMR) spectrum and 13C solid NMR spectrum. Thermogravimetric (TG) analysis showed that the residue of PPMA was remarkably higher than that of PPSA during the thermal decomposition process. When they were used to flame retard EVA, PPMA showed higher efficiency than PPSA for passing the UL-94 V-0 rating, increasing the oxygen index (OI), and decreasing the total heat release (THR) and total smoke production (TSP); while the PPSA was more efficient in decreasing the peak of heat release rate (PHRR) and the peak of smoke production rate (peak SPR). The investigation for the pyrolysis products of PPMA and PPSA demonstrated that various aromatic structures were produced due to the dehydrogenation of piperazine ring during the decomposition of PPMA and PPSA, which endowed them with excellent charring capability, and the charring efficiency of PPMA was higher than that of PPSA. However, the PPSA with lower charring capability tended to decompose and cyclize to the imides and volatilize into the gas phase, which resulted in the more ideal microstructure of PPSA system than that of PPMA system, finally led to the lower PHRR and peak SPR of PPSA system in cone calorimeter test.
Co-reporter:Hai-Yi Zhong;Li Chen;Xiao-Feng Liu;Rong Yang
Journal of Materials Chemistry C 2017 vol. 5(Issue 37) pp:9702-9711
Publication Date(Web):2017/09/28
DOI:10.1039/C7TC02393F
Novel liquid crystalline copolyesters named as P(BH-co-BPn)PS, with azobenzene and biphenyl group mesogenic units, were designed and synthesized conveniently by one pot melt polycondensation. All P(BH-co-BPn)PS copolyesters showed good thermal stability, smectic liquid crystalline behavior with π–π interactions in the polymer chains. As the three different functional building blocks (azobenzene and biphenyl chromophores, liquid crystals, π–π interactions) work together, P(BH-co-BPn)PS were responsive to external stimuli at the molecular level, exhibiting thermal shape memory, photo-induced bending and self-healing behaviors at the macroscopic level. It was noteworthy that the different responsive properties of the photo-active azobenzene and photo-inert biphenyl mesogenic units made a great contribution in the photo responsive behavior of these copolyesters, resulting in reversible bending and unbending behaviors for P(BH-co-BP30)PS. In addition, without the chemical crosslink, these copolyesters could be reshaped and reprocessed. Taking advantage of the features, these copolyesters containing amphi-mesogenic units can help to facilitate numerous applications like soft actuators and smart materials.
Co-reporter:Hai-Yi Zhong;Li Chen;Rong Yang;Zhi-Ying Meng;Xiao-Min Ding;Xiao-Feng Liu
Journal of Materials Chemistry C 2017 vol. 5(Issue 13) pp:3306-3314
Publication Date(Web):2017/03/30
DOI:10.1039/C6TC05493E
An azobenzene-containing thermotropic liquid crystalline polyester showing unique thermo- and photo-responsive behaviours was synthesized by polycondensation from mesogenic dial 4,4′-bis(6-hydroxyhexyloxy)azobenzene (BHHAB) with 2-phenylsuccinic acid (PSA), and named as poly(4,4′-bis(6-hydroxyhexyloxy)azobenzene phenylsuccinate) (PBHPS). Liquid crystalline behaviours were investigated through differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and wide-angle X-ray diffraction (WAXD). PBHPS showed a smectic phase with strong π–π interactions between the adjacent phenyl rings or between the side group and mesogenic unit, which could be regarded as physical crosslinking points that made PBHPS have good shape memory and self-healing properties. A series of PBHPS/methylcellulose bilayer films were prepared to study the reversible photo-mechanical properties. UV-vis absorption spectra were used to study the reversible photo-responsive behaviour of the polyester, proving that the reversible photoisomerization-induced volume expansion of the PBHPS layer resulted in good reversible photo-responsive properties.
Co-reporter:Dan Shen, Ying-Jun Xu, Jia-Wei Long, Xiao-Hui Shi, Li Chen, Yu-Zhong Wang
Journal of Analytical and Applied Pyrolysis 2017 Volume 128(Volume 128) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.jaap.2017.10.025
•Additive-type flame retardant for epoxy resin was conveniently prepared via neutralization between DOPA and melamine.•Flame retardance of the resulting material was significantly improved.•Pyrolysis behavior was comprehensively investigated by Py-GC/MS and TG-FTIR.•Flame retardant played the role of flame retardance in both condensed and gaseous phases.A melamine-organophosphinic acid salt (MDOP) was synthesized via neutralization of dibenzo[c,e][1,2]oxaphosphinic acid (DOPA) with melamine, and used as an additive-type flame retardant for epoxy resin (EP). Thermal stability and flame retardance was comprehensively evaluated via thermogravimetric analysis (TGA), UL-94 vertical burning test, limiting oxygen index (LOI) and cone calorimetry. The cured epoxy easily passed UL-94 V-0 rating with 0.33% content of P (5 phr MDOP); and LOI value of 38.0% was further achieved with 10 phr MDOP. The peak heat release (PHRR), total heat release (THR), total smoke production (TSP) and fire growth rate (FIGRA) were all reduced with the incorporation of MDOP. The pyrolysis behavior of the flame-retardant EP systems from Py-GC/MS and TG-FTIR suggested that MDOP played the role of flame retardance in both condensed and gaseous phases. Interestingly, the incorporation of MDOP did not deteriorate the mechanical properties of epoxy resin.
Co-reporter:Xue Dong, Rong-Tao Duan, Yan-Peng Ni, Zhi-Jie Cao, Li Chen, Yu-Zhong Wang
Polymer Degradation and Stability 2017 Volume 146(Volume 146) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.polymdegradstab.2017.09.022
•A series of imidized norbornene-containing PET copolyesters were successfully prepared.•Flame retardancy of the copolyesters was improved as a result of cross-linking between the imidized norbornene groups.•Cross-linking and rDA reaction happened at the same time, exhibiting a competitive relationship between each other.Retro-Diels-Alder reaction (rDA) has been widely used as a common modification approach for expanding functional applications of polymers. Especially, it has become an effective method of current cross-linking chemistry. With the goal of designing a cross-linkable PET-based copolyester toward flame retardancy and anti-dripping during combustion, dimethyl 5-(1,3-dioxo-3a,4,7,7a-tetrahydro-1H-4,7-methanoisoindol-2(3H)-yl) isophthalate (DMTMI) was incorporated as the functional co-monomer into PET chains via random transesterification polycondensation. Thermogravimetry-differential scanning calorimetry (TG-DSC) and rheological studies demonstrated the existence of cross-linking behavior at high temperature. By controlling the co-monomer content, expected flame retardancy was obtained, as illustrated by the results from the limiting oxygen index (LOI) and cone calorimetry. Furthermore, LOI values increased firstly and then decreased with the content of DMTMI increased, which was related to the existence of rDA reaction, and further proposed that a competitive relationship between the release of inflammable cyclopentadiene during rDA reaction and cross-linking behavior occurred in combustion. The hypothesis was verified through pyrolysis-gas chromatograph-mass spectrometry (Py-GC-MS).
Co-reporter:Chang-Lian Xu
Advanced Materials Interfaces 2017 Volume 4(Issue 17) pp:
Publication Date(Web):2017/09/01
DOI:10.1002/admi.201700550
Superhydrophobic surfaces have aroused great attention to fundamental and scientific researches. However, they have poor durability when they are exposed to a condition of high temperature or external forces. Herein, a durable superhydrophobic cellulose film against extreme high temperature and mechanical force is reported. ZnO nano- and microrods are constructed on cellulose using an effective, simple, and environmentally benign one-step hydrothermal method without any crystal seeds or morphology controlling agents. After being modified with stearic acid, the cellulose film becomes superhydrophobic with a static contact angle of 154.1° and rolling angle of 6.9°. The superhydrophobic cellulose film shows excellent water-repellent property even under dynamic water pressure, while it exhibits oleophilic nature under water, which can solve water pollution caused by heavy oil residuals. It is further found that it displays durable superhydrophobicity even if heated at 200 °C for 1 h or strongly scratched by knife. And heat treated films have better stability of superhydrophobicity under extreme condition with pH region from 3 to 11. These properties facilitate its applications of harsh conditions.
Co-reporter:A-Hui Kang, Ke Shang, Dan-Dan Ye, Yu-Tao Wang, Han Wang, Zong-Min Zhu, Wang Liao, Shi-Mei Xu, Yu-Zhong Wang, David A. Schiraldi
Chemical Engineering Journal 2017 Volume 327(Volume 327) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.cej.2017.06.158
•A waste of fly ash is used for flame retardant lightweight aerogel.•The ratio of the utilized waste fly ash is as high as 76.5 wt%.•Oxides in the fly ash particles remarkably suppress heat release and smoke release in fire.As a by-product of thermal power plants, a large amount of fly ash (FA) was produced every year. The comprehensive utilization of fly ash has been receiving increasing attention around the world. In this paper, FA simply modified with NaOH was used to enhance the flame retardancy of poly(vinyl alcohol) (PVA)/Laponite (Lap) aerogels via an environmentally friendly freeze-drying method. From the cone calorimetry test, it was obvious that the heat release rate, total heat release, smoke produce rate and total smoke production of the composite aerogels were decreased significantly with the addition of FA. When the content of fly ash exceeded 63.6 wt%, the limiting oxygen index exceeded 60.0%. All the PVA/Lap/FA aerogels reached V-0 ratings in vertical burning test. The thermal stabilities of the PVA/Lap/FA aerogels improved compared with PVA/Lap aerogels by thermogravimetric analysis. The addition of FA can effectively reduce the calorific value of aerogels, and achieved 2.50 MJ/kg when the FA content reached 76.5 wt%. After disposed with ultrasonic cell crusher, the PVA/Lap/FA mixtures became more homogeneous and form the more regular microstructures after freeze-drying, meanwhile, the pore size became smaller with the increase of FA. The PVA/Lap/FA aerogels exhibited stronger mechanical properties, which compression modulus and strength enhanced a lot than PVA/Lap aerogels. The introduction of FA into PVA/Lap aerogels improved their flame retardant properties successfully, demonstrating it a fire safety product. The content of FA has been achieved more than 50 wt% which provided a new method for efficient utilization of FA.
Co-reporter:Ai-Hua Yang, Cong Deng, Hong Chen, Yun-Xia Wei, Yu-Zhong Wang
Polymer Degradation and Stability 2017 Volume 144(Volume 144) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.polymdegradstab.2017.08.007
A novel Schiff-base polyphosphate ester (SPE) flame retardant was synthesized through melt polycondensation, and used to flame retard thermoplastic polyurethane elastomer (TPU). The SPE possessed high thermal stability and rich char residue under high temperature according to the thermogravimetric (TG) analysis. In combustion tests, the flame-retarded TPU passed the UL-94 V-0 rating, and had a limited oxygen index (LOI) of 29% when the content of SPE was only 5 wt%, meanwhile, the amount of dripping remarkably reduced. In cone calorimetry test, the peak of heat release rate (pHRR), average mass loss rate (AMLR), and maximum average rate of heat emission (MARHE) of the flame-retarded TPU with 5 wt% SPE were respectively decreased by 61.7%, 41.8%, and 30.2% compared with the corresponding value of neat TPU. All these results demonstrated that the SPE simultaneously improved the flame retardancy and dripping behavior of TPU. Thermogravimetric-Fourier transform infrared spectra (TG-FTIR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and laser Raman spectroscopy (LRS) illustrated that SPE simultaneously played a flame-retardant role in both condensed phase and gas phase.
Co-reporter:Ke Shang, Dan-Dan Ye, A-Hui Kang, Yu-Tao Wang, Wang Liao, Shimei Xu, Yu-Zhong Wang
Polymer 2017 Volume 131(Volume 131) pp:
Publication Date(Web):22 November 2017
DOI:10.1016/j.polymer.2017.07.022
•A novel ‘melt-crosslink’ method is developed.•The mechanical strength of the aerogel increases ca. 4-fold.•Reduction of PHRR (−60%) and THR (−49%) are significant.A highly robust and flame retardant borate-crosslinked poly (vinyl alcohol)/montmorillonite aerogel is fabricated through a novel melt-crosslink method. In this way, the PVA/MMT hydrogel was prepared by immersing the frozen PVA/MMT sol into a borax solution, inducing crosslinking between diols of PVA and borate exactly during the ice melt. As a result, rearrangement of the polymer chains and subsequent expansion result in finer and more compact network. The corresponding aerogel is obtained by freeze-drying. The optimal crosslinking conditions, including the borax concentration and crosslinking time, are determined by rheology of the hydrogels. This method provides a new idea for the preparation of crosslinked aerogels and improvement of mechanical and flame retardant properties simultaneously. The mechanical strength of the crosslinked aerogel is relatively high among the existing fire safety polymer/nanoclay composite aerogels with 30%–60% loading of inorganic matters at a low density level. The flame retardant properties are indicated by significant improvements of limiting oxygen index (LOI) to a value of 27.6% and achievement of UL-94 V-0 rating and remarkable decrease of the fire indexes in cone calorimetry (CC) test. The combustion behaviors are further studied by the results of SEM, energy dispersive X-ray spectrometer (EDX) and X-ray photoelectron spectroscopy (XPS).Download high-res image (330KB)Download full-size image
Co-reporter:Man-Jie He;Wen-Xia Xiao;Hui Xie;Cheng-Jie Fan;Lan Du;Xiao-Ying Deng;Ke-Ke Yang
Materials Chemistry Frontiers 2017 vol. 1(Issue 2) pp:343-353
Publication Date(Web):2017/02/16
DOI:10.1039/C6QM00047A
How to realize the multi-stimuli-response of shape-memory polymers in a simple system is a big challenge for researchers. In this study, a facile approach to produce a series of ternary nanocomposites made of a poly(butylene succinate)–poly(ε-caprolactone) (PBSPCL) multiblock copolymer matrix and multi-walled carbon nanotubes (MWCNTs) is described. MWCNTs were easily introduced into the double-crystalline copolymer matrix using solution mixing and solvent casting processes, successively. As a consequence of the immiscibility between these two polymeric segments, the spontaneous selective dispersion of MWCNTs is realized in the matrix with refined microphase separation morphology. The different affinity of MWCNTs for the PBS or PCL segment drove the MWCNTs to be localized in the PBS domain preferentially, as demonstrated by TEM analysis. This elaborate design leads to a significant reduction of percolation thresholds with the optimized composition of the nanocomposites. Moreover, the selective dispersion of MWCNTs in the hard PBS segment improved the strength of the material without deteriorating its ductility. Dynamic thermomechanical tests revealed that the PBSPCL copolymers exhibit an excellent dual-shape memory effect, as attested by the fix ratio (Rf) and recovery ratio (Rr) of 98%. After incorporation of MWCNTs into the matrix, the electro- and NIR-induced shape-memory effects have been realized, and the sample containing 40% PBS segment and 1 wt% MWCNTs exhibits optimal structure and performance.
Co-reporter:Juan Wang, Dan Zhao, Ke Shang, Yu-Tao Wang, Dan-Dan Ye, A.-Hui Kang, Wang Liao and Yu-Zhong Wang
Journal of Materials Chemistry A 2016 vol. 4(Issue 24) pp:9381-9389
Publication Date(Web):23 May 2016
DOI:10.1039/C6TA03146C
We demonstrated the preparation of a novel aerogel simply by cross-linking a gelatin physical gel with formaldehyde (cGel) and using a subsequent freeze-drying procedure. A hydrophobic absorbent material (MTCS-cGel aerogel) was further obtained by thermal chemical vapor deposition (CVD) of methyltrichlorosilane (MTCS). Rheological tests were carried out to investigate the cross-linking between gelatin and formaldehyde. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and wettability of oil and water results proved that successful silanization occurred on/in the aerogels. These results also indicated that the MTCS-cGels had low densities (5–8 kg m−3), high porosities (>95%) with uniform pore sizes, and unique laminar/fibrous 3D networks. The oleophilic aerogels possessed high oil absorption capacities of 70–123 times that of their dry weights. Furthermore, the absorbents exhibited excellent elasticity and ultrasoftness with a stress of only 2.0 kPa at 60% strain. This property endowed the aerogels with super-recyclability where 83–85% of their full absorption capacity was maintained after 5000 times of compression. The high oil absorption performance, super-recyclability, sustainability, biodegradability and cost-efficiency make this novel absorbent a promising candidate for large-scale oceanic oil contaminant removal.
Co-reporter:Ke Shang, Wang Liao, Juan Wang, Yu-Tao Wang, Yu-Zhong Wang, and David A. Schiraldi
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 1) pp:643
Publication Date(Web):December 16, 2015
DOI:10.1021/acsami.5b09768
Nonflammable materials based on renewable ammonium alginate and nano fillers (nanoscale magnesium hydroxide, nanoscale aluminum hydroxide, layered double hydroxide, sodium montmorillonite, and Kaolin) were fabricated through a simple, environmentally friendly freeze-drying process, in which water was used as a solvent. A simple and economic post-cross-linking method was used to obtain homogeneous samples. The microstructure of the cross-linked alginate aerogels show three-dimensional networks. These materials exhibit low densities (0.064–0.116 g cm–3), low thermal conductivities (0.024–0.046 W/m K), and useful mechanical strengths (0.7–3.5 MPa). The aerogels also exhibit high thermal stabilities and achieve inherent nonflammability with limiting oxygen indexes (LOI) higher than 60. Related properties were conducted and analyzed by cone calorimeter (CC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). These results combine to suggest promising prospects for use of these aerogel nanocomposites in a range of applications.Keywords: aerogel; alginate; flame retardant; freeze-drying; post-cross-linking; thermal insulation
Co-reporter:Xue-Bao Lin, Shuang-Lan Du, Jia-Wei Long, Li Chen, and Yu-Zhong Wang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 1) pp:881
Publication Date(Web):December 28, 2015
DOI:10.1021/acsami.5b10287
An organophosphorous hybrid (BM@Al-PPi) with unique core–shell structure was prepared through hybridization reaction between boehmite (BM) as the inorganic substrate and phenylphosphinic acid (PPiA) as the organic modifier. Fourier transform infrared spectra (FTIR), solid state 31P and 27Al magic angle spinning nuclear magnetic resonance, X–ray diffraction, and element analysis were used to investigate the chemical structure of the hybrids, where the microrod–like core was confirmed as Al-PPi aggregates generated from the reaction between BM and PPiA, and those irregular nanoparticles in the shell belonged to residual BM. Compared with the traditional dissolution–precipitation process, a novel analogous suspension reaction mode was proposed to explain the hybridization process and the resulting product. Scanning electronic microscopy further proved the core–shell structure of the hybrids. BM exhibited much higher initial decomposition temperature than that of Al-PPi; therefore, the hybrid showed better thermal stability than Al-PPi, and it met the processing temperature of semi–aromatic polyamide (HTN, for instance) as an additive-type flame retardant. Limiting oxygen index and cone calorimetric analysis suggested the excellent flame-retardant performance and smoke suppressing activity by adding the resulting hybrid into HTN.Keywords: boehmite; flame retardance; hybrid; phenylphosphinic acid; semiaromatic polyamide; thermal stability
Co-reporter:Yi Tan, Zhu-Bao Shao, Lei-Xiao Yu, Jia-Wei Long, Min Qi, Li Chen and Yu-Zhong Wang
Polymer Chemistry 2016 vol. 7(Issue 17) pp:3003-3012
Publication Date(Web):13 Apr 2016
DOI:10.1039/C6PY00434B
To obtain highly fire-safe epoxy resin (EP), piperazine-modified ammonium polyphosphate (PAz-APP) with multiple active –NH– groups was prepared and utilized as a highly effective flame-retardant hardener. After curing by PAz-APP as a monocomponent hardener, cross-linked networks containing both tertiary amino and ether linkages were obtained, which resulted in two glass transitions. Thanks to the phosphorus-containing inorganic part, PAz-APP brought excellent flame retardance and smoke suppression efficiency to the EP system. The cured sample passed V-0 rating (UL-94) with only 7.5 wt% addition of PAz-APP. Cone calorimetric results suggested that, compared with PAz/EP (as a reference sample), both the peak-heat release rate (PHRR) and total smoke production (TSP) of PAz-APP 15/EP (15 wt% addition) sharply dropped by 81.5% and 80.0%, respectively. By analyzing the chemical constitution of the decomposing residues at different temperatures, it was noticed that PAz-APP mainly acted as a flame retardant in the condensed phase via the formation of phosphorus-rich char. Dynamic mechanical analysis (DMA) illustrated that the main glass transition temperature (Tg) of PAz-APP 15/EP was as high as 162.4 °C. Furthermore, the incorporation of PAz-APP did not worsen the mechanical properties, but contrarily, improved the impact strength.
Co-reporter:Xue Dong, Li Chen, Rong-Tao Duan and Yu-Zhong Wang
Polymer Chemistry 2016 vol. 7(Issue 15) pp:2698-2708
Publication Date(Web):14 Mar 2016
DOI:10.1039/C6PY00183A
The concept of incorporating cross-linkable precursor as the copolymerizing monomer has been proved efficient for polyesters to achieve low flammability and anti-dripping property. Adapting this concept, in our latest paper, a new co-monomer named 5-(2,5-dioxo-3-phenyl-2,5-dihydro-1H-pyrrol-1-yl) isophthalic acid (DPDPI) was synthesized and incorporated into PET chain. Results from limiting oxygen index (LOI), UL-94 and the cone calorimetric test demonstrated that these PET-co-DPDPI copolyesters possess excellent flame retardance and anti-dripping performance. UL-94 V-0 rating could be achieved with a DPDPI content of as low as 10 mol% (PET-co-DPDPI10). Results from thermogravimetry-differential scanning calorimetry (TG-DSC) and dynamic oscillatory rheology proved the existence of the cross-linking behaviour during heat. The cross-linked polymer structures were stable at high temperature and could promote the char formation during burning. According to the results of Raman spectroscopy, X-ray photoelectron spectrometry (XPS) and pyrolysis/gas chromatography-mass spectrometry (Py/GC-MS), the cross-linking and flame-retardant mechanism were proposed for PET-co-DPDPIX, that during combustion, 2π + π cycloaddition which occurred between the phenylmaleimide groups as the cross-linking reaction. Afterward, the cross-linked networks promoted aromatization and carbonization, which resulted in self-extinguishing and anti-dripping.
Co-reporter:Teng Fu, De-Ming Guo, Jia-Ning Wu, Xiao-Lin Wang, Xiu-Li Wang, Li Chen and Yu-Zhong Wang
Polymer Chemistry 2016 vol. 7(Issue 8) pp:1584-1592
Publication Date(Web):19 Jan 2016
DOI:10.1039/C5PY01938A
Inherent flame-retardant semi-aromatic polyesters, containing special aryl ether and/or ketone structures (“Ar–CO–Ar”, “Ar–O–Ar”, “Ar–O–Ar–O–Ar” or “Ar–O–Ar–CO–Ar–O–Ar”) were synthesized successfully. Interestingly, these polyesters show different flame retardancy beyond our traditional knowledge that more benzene rings are beneficial to flame retardancy. The polyester containing “Ar–O–Ar–O–Ar” shows excellent flame retardancy, whose LOI value reaches 34.1% and the UL-94 rating is V-0. Meanwhile, the polyester with the “Ar–O–Ar–CO–Ar–O–Ar” structure does not perform expectedly well (31.6% and V-2 rating respectively). In order to make clear the effect of aryl ether and/or ketone structure units on the flame retardancy, the pyrolysis behaviours and the char residue are investigated by Py-GC/MS, TGA, and SEM. In the TGA test, the char residues of polyesters containing “Ar–CO–Ar”, “Ar–O–Ar” “Ar–O–Ar–O–Ar” or “Ar–O–Ar–CO–Ar–O–Ar” are 31.6%, 22.5%, 30.6% or 38.7%, respectively. These values do not match with the calculated results, which indicate that some special reactions occur during combustion. Furthermore, these polyesters show a common initial pyrolysis pathway and subsequent unique processes in the Py-GC/MS test. Their pyrolysis intermediate products can bind small-molecule free radicals, and eventually form different conjugated aromatic structures. In this way, inherent flame-retardant polyesters are obtained even without any traditional flame-retardant elements. And their flame retardant performance has great relationship with the amount of char formation, the microstructure of char, and the chemical structure of pyrolysis products.
Co-reporter:Rong-Tao Duan, Qiu-Xia He, Xue Dong, De-Fu Li, Xiu-Li Wang, and Yu-Zhong Wang
ACS Sustainable Chemistry & Engineering 2016 Volume 4(Issue 1) pp:350
Publication Date(Web):December 3, 2015
DOI:10.1021/acssuschemeng.5b01335
In order to improve the mechanical and oxygen barrier properties of poly(butylene succinate) (PBS), two series of sugar-containing PBS copolyesters with different molecular stiffness were synthesized and comparatively investigated, in which a cyclic alditol, isosorbide (Is) or 2,3-O-isopropylidene-l-threitol (ITh) was, respectively, used as a comonomer. Both cyclic alditols were easily available from biomass feedstock, such that Is is a bicyclic compound derived from d-glucose, and ITh is a monocyclic acetalized compound coming from naturally occurring l-tartaric acid. All these copolyesters containing up to 30 mol % of sugar-based units had satisfactory number-average molecular weights in the 16 000–83 000 g mol–1 range, and presented a random microstructure together with excellent thermal stability. The sugar-containing copolyesters were all semicrystalline and still possessed the monoclinic crystal structure of PBS. The incorporation of either Is or ITh units with rigid cyclic structure into PBS chain decreased the crystallinity and crystallization rate of PBS, while it enhanced its glass transition temperature. In addition, the partial replacement of 1,4-butanediol by sugar-based units endowed PBS with steadily enhanced hydrophilicity. Depending on the type and content of sugar units, the copolyesters show different oxygen barriers and mechanical properties. It was found that copolyester with bicyclic Is sugar units exhibited a better oxygen barrier and mechanical property than that with monocyclic ITh units.Keywords: 2,3-O-Isopropylidene-l-threitol; Crystallization; Isosorbide; Mechanical property; Oxygen barrier property; Poly(butylene succinate); Thermal stability
Co-reporter:Ying-Ming Li, Cong Deng, Yu-Zhong Wang
Composites Science and Technology 2016 Volume 132() pp:116-122
Publication Date(Web):23 August 2016
DOI:10.1016/j.compscitech.2016.07.007
A novel ethylene-vinyl acetate (EVA) composite for cables and insulated wires was prepared through incorporating glass powder (GP), mica powder (MP) and organo-modified montmorillonite (OMMT) into the EVA. Mechanical test showed that the tensile strength of EVA/GP/MP/OMMT composite with the ratio of 55/23/17/5 was 8.5 MPa, and its elongation at break was 790%; for its ceramics formed at 700 °C, the flexural strength reached to 11.8 MPa, and the volume resistivity was 3.87 × 1011 Ω/cm. Thermal gravimetric analysis (TGA) showed that the initial thermal decomposing temperature of EVA/GP/MP/OMMT (55/23/17/5) was about 350 °C, and the residue was about 58.2%. The ceramics formed at high temperature were investigated by infrared spectroscopy (IR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The IR and XRD results demonstrated that the structure of MP was destroyed at high temperature, and a eutectic mixture was formed. SEM observation illustrated that the interface of the ceramics became fuzzy with increasing the GP, and the fluoramphibole crystals were formed at high temperature due to the presence of Na2O, CaO, etc. All these experimental results demonstrated that the ceramization of mica-based EVA composite was achieved successfully, and the formed ceramics had excellent mechanical properties and insulativity.
Co-reporter:Gui-Cheng Liu, Wen-Qiang Zhang, Shui-Lian Zhou, Xiu-Li Wang and Yu-Zhong Wang
RSC Advances 2016 vol. 6(Issue 73) pp:68942-68951
Publication Date(Web):14 Jul 2016
DOI:10.1039/C6RA13488B
To improve the processability and crystallization of poly(butylene succinate) (PBS), a cross-linkable comonomer containing an alkynyl group, named 5-(2-(trimethylsilyl)ethynyl)isophthalate (DTS) was synthesized and copolymerized with dimethyl succinate and 1,4-butanediol to prepare a series of slightly cross-linked PBS copolyesters (PBDTSx). Due to the very low cross-linking degree, PBDTSx do not form gels when the DTS molar content is lower than 1.0%, and this made them keep good solubility and reprocessability. The cross-linking degree of DTS in PBDTSx is determined by NMR spectra. GPC data show that the Mw values of the copolyesters are higher than 23 × 104 g mol−1, and increase with the increase of DTS content. The thermal stability, crystallization, rheological behaviours, and mechanical properties of PBDTSx were investigated. Compared to neat PBS, PBDTSx have greatly increased crystallization rates because of promoted nucleation of the cross-linking domains. The elongation at break of PBDTSx drops slightly, while the Young's modulus increases. The rheological behaviours indicate that PBDTSx have higher melt viscosity than neat PBS even at a high shear rate, meaning that they will have better blow moulding processability. This work demonstrates that via controlling tiny cross-linking during the polymerization of PBS, the properties and processability of PBS can be improved, and this method overcomes the defects caused by traditional post cross-linking.
Co-reporter:Liang-Ping Dong, Cong Deng, Rui-Min Li, Zhi-Jie Cao, Ling Lin, Li Chen and Yu-Zhong Wang
RSC Advances 2016 vol. 6(Issue 36) pp:30436-30444
Publication Date(Web):17 Mar 2016
DOI:10.1039/C6RA00164E
Traditional charring agents have two obvious defects, which are low charring efficiency and bad interaction with the other flame-retardant components, leading to the unsatisfying efficiency of an intumescent flame retardant. To overcome the aforementioned disadvantages, a novel phosphorus and nitrogen compound, named poly(piperazinyl phosphamide) (PPPA), was synthesized through a one-step reaction. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) etc., confirmed that PPPA was prepared successfully. Thermogravimetric analysis (TGA) revealed that the char residues of PPPA at 600 °C under N2 and air were 45.3 wt% and 51.6 wt%, respectively. Combustibility tests including oxygen index (OI), vertical burning test (UL-94) and cone calorimeter test (CC) further proved that the PPPA was a highly efficient charring agent from the viewpoint of its application. The OI value of the ethylene-vinyl acetate copolymer (EVA)/ammonium polyphosphate (APP)/PPPA composite reached 30.5%, and it passed the V-0 rating in the presence of only 5.5 wt% PPPA. The Py-GC/MS, FTIR and XPS tests demonstrated that abundant aromatic structures resulting from the decomposition of the PPPA, mainly consisting of CC, CN, P–N and PO etc., facilitated the formation of a stable char layer. Moreover, APP could delay the fracture of the C–N bond in PPPA and catalyze the generation of the benzene ring, further enriching the char residue. So, both the highly-efficient charring capacity of PPPA itself and the synergetic effect resulting from APP and PPPA led to the excellent flame retardation of the EVA composite.
Co-reporter:Liang-Ping Dong, Sheng-Chao Huang, Ying-Ming Li, Cong Deng, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 26) pp:7132-7141
Publication Date(Web):June 14, 2016
DOI:10.1021/acs.iecr.6b01308
A novel linear-chain polyamide charring agent named poly(piperazinyl oxalamide) (PPOA) was prepared successfully. Thermogravimetric analysis (TGA) proved that PPOA had a charring capability that was better than those of traditional polyamide charring agents. After incorporation of PPOA into ethylene-vinyl acetate copolymer/ammonium polyphosphate (EVA/APP), the flame retardancy of EVA/APP was dramatically improved. At 25.0 wt % APP/PPOA(3:1), the OI value of the EVA/APP/PPOA system was 31.5%; its UL-94 rating was V-0. Both the peak of heat release rate (PHRR) and the peak of smoke production rate (peak SPR) for the EVA/APP/PPOA system decreased remarkably compared with that of EVA containing 25.0 wt % APP. The analysis of the charring mechanism of PPOA demonstrated that abundant heterocyclic aromatic structures were formed during the decomposition of PPOA, which endowed the PPOA with excellent charring capability and resulted in the low risk of combustion of the EVA/APP/PPOA system.
Co-reporter:Shi-Bi Deng, Wang Liao, Jun-Chi Yang, Zhi-Jie Cao, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 27) pp:7239-7248
Publication Date(Web):June 16, 2016
DOI:10.1021/acs.iecr.6b00532
Flexible silicone foams (SiFs) are high-performance but flammable materials that emit dense smoke in a fire. Two type of low-cost, eco-friendly nanocoatings, i.e., chitosan (CH)/ammonium polyphosphate (APP) and CH/montmorillonite (MMT), were fabricated on SiFs through a layer-by-layer (LbL) assembly. With seven bilayers (BL) of CH/APP coatings, the limiting oxygen index (LOI) increases from 20.2% to 23.8%, the peak heat release rate (pHRR) decreases by 27.6%, and the total smoke production (TSP) decreases 42%. Further deposition of CH/APP, however, partly damaged the fire resistance. In contrast, fire hazard and smoke release of CH/MMT coated SiFs were monotonously reduced. Every 7 BL of coating leads to ca. 12% reduction of TSP. Moreover, thermogravimetric analysis (TGA) was used to follow the pyrolysis of the coated foams, and scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX) were applied to analyze the char residues systematically.
Co-reporter:Dan-Yang Xie, Fei Song, Mei Zhang, Xiu-Li Wang, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 5) pp:1229-1235
Publication Date(Web):January 19, 2016
DOI:10.1021/acs.iecr.5b04185
Waterborne polyurethanes (WPUs) with varying lengths of soft segment were synthesized and used to physically modify soy protein isolate (SPI), a protein with good film-forming ability and oxygen barrier characteristic but poor toughness and water resistance, via a simple blending technique without any compatibilizer. The effects of soft segment structure of WPU on the structure and property of resultant blend films were investigated. The tensile strength, elongation at break, and water resistance of the SPI-based films were improved and modulated by adding WPUs with different lengths of soft segment. Compared with neat SPI film, the equilibrium water uptake was decreased by 138% at most for a blend film, and the tensile strength and elongation at break were improved by 96% and 82%, respectively. All the blend films possessed uniform cross-section structures due to the strong interactions between SPI and WPU. Moreover, the blend films exhibited a satisfied water vapor barrier property. It was proved that the modification of SPI with WPU might be an effective way to fabricate SPI-based films for practical applications.
Co-reporter:Yi Tan, Zhu-Bao Shao, Lei-Xiao Yu, Ying-Jun Xu, Wen-Hui Rao, Li Chen, Yu-Zhong Wang
Polymer Degradation and Stability 2016 Volume 131() pp:62-70
Publication Date(Web):September 2016
DOI:10.1016/j.polymdegradstab.2016.07.004
To expand the application of ammonium polyphosphate (APP) in epoxy resin (EP), hyperbranched polyethyleneimines (PEI) were selected to modify it via cation exchange reaction. Then, a highly-efficient flame-retardant hardener with poly-functionalities for EP was successfully prepared and named as PEI-APP. After curing, PEI-APP endowed the EP samples with good flame retardance and smoke suppression performance. Results suggested the total heat release (THR) and total smoke production (TSP) decreased 76.1% and 70.5% respectively. Thermogravimetric analyses (TGA) of the PEI-APP cured EPs displayed a slight improvement in the high temperature region compared with the reference sample (PEI/EP). Dynamic mechanical analysis (DMA) demonstrated that the glass transition temperature (Tg) of PEI-APP/EP also slightly increased compared with PEI/EP. Fourier transform infrared spectra (FTIR) was used to analyse the condensed products of PEI-APP/EP samples at different temperatures to investigate the flame-retardant mechanism. All the aforementioned results distinctly confirmed that PEI-APP did not only act as an effective flame-retardant hardener for EP, but also brought a good thermal stability and improved the smoke suppression to the system. This polyamine hardener provided a new platform for intumescent flame-retardant application in EP.
Co-reporter:Yu-Zhong Wang;Yun-Xuan Weng
Science China Chemistry 2016 Volume 59( Issue 11) pp:1353-1354
Publication Date(Web):2016 November
DOI:10.1007/s11426-016-0384-4
Co-reporter:Hui Xie, Chuan-Ying Cheng, Lan Du, Cheng-Jie Fan, Xiao-Ying Deng, Ke-Ke Yang, and Yu-Zhong Wang
Macromolecules 2016 Volume 49(Issue 10) pp:3845-3855
Publication Date(Web):May 9, 2016
DOI:10.1021/acs.macromol.6b00382
Covalently cross-linked network has been widely applied in triple-shape memory polymers (TSPs), and fabricating triple-shape memory networks with the optional shapes through a facile and fast way is highly expected in the real applications. In this study, a “preshaped and post-cross-linking” strategy has been put forward to fabricate the triple-shape networks via fast photo-cross-linking in solid state. The photoresponsive anthracene group was first employed to develop a poly(d,l-lactide)–poly(tetramethylene oxide) glycol (PDLLA-PTMEG) network via UV light irradiation. Two steps were involved in network fabrication: first, linear copolymers (AN-PDLLA-PTMEG) containing anthracene groups on the side chains with different mass ratio of PDLLA segments were synthesized, and then PDLLA-PTMEG networks (NW-PDLLA-PTMEG) were formed by 365 nm UV light irradiation under an argon atmosphere. The structures of all the precursors were determined by 1H NMR, and all networks were evaluated by swelling tests. The results of tensile tests show that the content of PDLLA segments has a crucial effect on the mechanical performance of the materials. Differential scanning calorimetry (DSC) analysis combined with dynamic mechanical analysis (DMA) reveals that all the NW-PDLLA-PTMEG’s display two thermal transitions (Tm,PTMEG and Tg,PDLLA), which can be utilized as Ttrans to trigger triple-shape memory behavior. The cyclic thermal mechanical testing for triple-shape effects of NW-PDLLA-PTMEG, which was performed by DMA, demonstrates that the mass ratio of two segments has a great effect on the shape fixity and shape recovery. Moreover, a practical application as heat-shrinkable tube (or film) has been put forward.
Co-reporter:Shi-fu Liao;Cong Deng 邓聪;Sheng-chao Huang
Chinese Journal of Polymer Science 2016 Volume 34( Issue 11) pp:1339-1353
Publication Date(Web):2016 November
DOI:10.1007/s10118-016-1855-8
In this study, piperazine-modified ammonium polyphosphates (PA-APPs) with hierarchical structure were synthesized through ion exchange reaction. 1H nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectra (FTIR), elemental analysis (EA), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) confirmed that the PA-APPs with different structures were prepared successfully. Then these flame retardants were used alone as monocomponent intumescent flame retardant for low-density polyethylene (LDPE). Combustion tests demonstrated that the flameretardant efficiency of PA-APP containing about 7 wt% carbon (PA-APP7) was significantly higher than that of the other PAAPPs with more or less carbon. The flame-retarded LDPE system with 30 wt% PA-APP7 passed the UL-94 V-0 rating, and had the oxygen index (LOI) of 33.0%. Thermal analysis illustrated that the thermal decomposition behavior of PA-APP changed with incorporating different contents of PA. For all these PA-APPs, PA-APP7 showed higher thermal stability than the other PA-APP flame retardants. All the experimental results proved that PA-APP7 could reach the balance of an acid source, a blowing source, and a charring source as a mono-component intumescent flame retardant for LDPE. Further, it led to the formation of a compact intumescent char layer containing the structures of rich P―O―P, P―N―C, C=C, etc. during burning which in turn resulted in the excellent flame-retardant efficiency of PA-APP7.
Co-reporter:Yi Tan, Zhu-Bao Shao, Xue-Fang Chen, Jia-Wei Long, Li Chen, and Yu-Zhong Wang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 32) pp:17919
Publication Date(Web):July 17, 2015
DOI:10.1021/acsami.5b04570
A novel multifunctional organic–inorganic hybrid was designed and prepared based on ammonium polyphosphate (APP) by cation exchange with diethylenetriamine (DETA), abbreviated as DETA-APP. Then DETA-APP was used as flame-retardant curing agent for epoxy resin (EP). Curing behavior, including the curing kinetic parameters, was investigated by differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). The flame retardance and burning behavior of DETA-APP cured EP were also evaluated. The limiting oxygen index (LOI) value of DETA-APP/EP was enhanced to 30.5% with only 15 wt % of DETA-APP incorporated; and the UL-94 V-0 rating could be easily passed through with only 10 wt % of the hybrid. Compared with DETA/EP, the peak-heat release rate (PHRR), total heat release (THR), total smoke production (TSP), and peak-smoke production release (SPR) of DETA-APP/EP (15 wt % addition), obtained from cone calorimetry, were dropped by 68.3, 79.3, 79.0, and 30.0%, respectively, suggesting excellent flame-retardant and smoke suppression efficiency. The flame-retardant mechanism of DETA-APP/EP has been investigated comprehensively. The results of all the aforementioned studies distinctly confirmed that DETA-APP was an effective flame-retardant curing agent for EP.Keywords: ammonium polyphosphate; curing; epoxy resin; flame retardance; hybrid
Co-reporter:Juan Xue, Fei Song, Xue-wu Yin, Xiu-li Wang, and Yu-zhong Wang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 19) pp:10076
Publication Date(Web):May 4, 2015
DOI:10.1021/acsami.5b02011
Exploration of environmentally friendly light-emitting devices with extremely low weight has been a trend in recent decades for modern digital technology. Herein, we describe a simple suction filtration method to develop a transparent and photoluminescent nanocellulose (NC) paper, which contains ZnSe quantum dot (QD) with high quantum yield as a functional filler. ZnSe QD can be dispersed uniformly in NC, and a quite low coefficient of thermal expansion is determined for the resultant composite paper, suggesting its good dimensional stability. These results indicate that the meeting of NC with ZnSe QD can bring a brilliant future during the information age.Keywords: flexibility; nanocellulose; photoluminescence; quantum dot;
Co-reporter:Lan Bai, Xiao-hui Wang, Fei Song, Xiu-li Wang and Yu-zhong Wang
Chemical Communications 2015 vol. 51(Issue 1) pp:93-96
Publication Date(Web):03 Nov 2014
DOI:10.1039/C4CC07012G
A dual-responsive drug delivery system simulating an AND logic gate is developed by core-cross-linking of a disulfide-containing anticancer prodrug with Cu2+ for safe and efficient delivery of anticancer drugs. These prodrug nanoparticles are stable and exhibit nearly no premature drug release, and allow a fast drug release under simulated intracellular conditions, realizing a precise drug delivery towards cell nuclei.
Co-reporter:Yu-Tao Wang, Shi-Fu Liao, Ke Shang, Ming-Jun Chen, Jian-Qian Huang, Yu-Zhong Wang, and David A. Schiraldi
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 3) pp:1780
Publication Date(Web):January 14, 2015
DOI:10.1021/am507409d
Ammonium polyphosphates (APP) modified with piperazine (PA-APP) was used to improve the flame retardancy of poly(vinyl alcohol) (PVA)/montmorillonite (MMT) aerogels, which were prepared via an environmentally friendly freeze-drying method. The thermal stabilities of the samples were evaluated by thermogravimetric analysis (TG); the flammability behaviors of samples were investigated by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter (CC) tests. TG test results showed that the 5% weight loss temperature (T5%) of PVA/MMT/PA-APP was 10 °C higher than that of PVA/MMT/APP. In combustion testing, all of PVA/MMT/PA-APP aerogels achieved V-0 ratings and have a higher LOI values than the unmodified PVA/MMT aerogel. Moreover, the aerogel with 1% PA-APP5, which means that the content of piperazine is 5% in PA-APP, decreased the cone calorimetry THR value to 5.71 MJ/m2, and increased the char residue to 52%. The compressive modulus of PVA/MMT/PA-APP was increased by 93.4% compared with PVA/MMT/APP because of the increase in interfacial adhesion between matrix and PA-APP fillers. The densities of the PVA/MMT/PA-APP samples were slightly lower than those of the unmodified aerogels because of reduced shrinkage in the presence of PA-APP. All the tests results indicated that the incorporation of PA-APP not only improved the thermal stability and flame retardancy of aerogels but also maintained their mechanical properties.Keywords: aerogel; ammonium polyphosphate; flame retardant; mechanical behavior; piperazine; poly(vinyl alcohol)
Co-reporter:Ze-Yong Zhao, Liang-Ping Dong, Li Chen and Yu-Zhong Wang
RSC Advances 2015 vol. 5(Issue 23) pp:17967-17975
Publication Date(Web):02 Feb 2015
DOI:10.1039/C5RA00450K
The influence of a high loading of magnesium hydroxide (Mg(OH)2, MDH) on the morphology and properties of polypropylene (PP)/ethylene–octene copolymer (POE) blends has been investigated via scanning electron microscopy, dynamic mechanical thermal analysis and tensile mechanical testing. It was demonstrated that the mechanical properties, especially the elongation at break, are highly related to the phase structure exhibited by the composites. In the PP/POE 90/10 and 70/30 blends, the addition of a high loading of MDH lowered the average diameter of the dispersed POE domains, also the MDH and POE domains were separately dispersed in the PP matrix. Meanwhile, the elongation at break of the samples sharply declined to an unacceptable level. While in the PP/POE 50/50 blends, a co-continuous structure was formed and it could be maintained even after a large amount of MDH was added. The co-continuous structure was found to be a key factor for tolerating high loading of additives and retaining acceptable mechanical properties, especially the elongation at break.
Co-reporter:Lan Bai, Fei Song, Xiao-hui Wang, Jiang-yong-quan Cao, Xue Han, Xiu-li Wang and Yu-zhong Wang
RSC Advances 2015 vol. 5(Issue 59) pp:47629-47639
Publication Date(Web):13 May 2015
DOI:10.1039/C5RA05747G
In the field of anticancer drug delivery, improving drug loading capacity of carriers and achieving efficient intracellular drug transportation simultaneously is very difficult but they are important issues for the development of chemotherapy. Herein, a reversible ligand–metal-drug coordination architecture responsive to pH was employed to construct a smart drug delivery system, in which the ligand and metal can be regarded as a harbor and an anchor to not only moor the drug (doxorubicin, DOX) but also send the cargo precisely on time. Based on the strategy, DOX loading content of the system could run up to 26.1%. Owing to the stability of coordination bonds at neutral conditions, premature drug leakage was extremely suppressed to lower than 5%, while an almost complete drug release was realized at pH 5.0 as a result of breakage of the bonds. Presence of the coordination interaction played a key role in controlled release of DOX, which followed the first-order kinetics model in the case of non-coordinated systems but the pseudo-second-order kinetics model in the case of coordinated systems. Moreover, the metal-coordinated system could effectively take DOX into HeLa cells, presenting a comparable cancer therapy effect to free DOX. This study established exploitation of coordination interaction to connect drugs and carriers as a promising way to meet urgent needs for chemotherapy.
Co-reporter:Hong-Wei Di, Cong Deng, Rui-Min Li, Liang-Ping Dong and Yu-Zhong Wang
RSC Advances 2015 vol. 5(Issue 63) pp:51248-51257
Publication Date(Web):02 Jun 2015
DOI:10.1039/C5RA05781G
Ethylene-vinyl acetate (EVA) filled with glass dust (GD), glass fiber (GF), OMMT, and melamine cyanurate (MCA) was developed as a ceramifiable flame-retardant polymer composite for cables and insulated wires. The ceramics formed at different high temperatures based on the ceramifiable flame-retardant polymer composites were investigated by mechanical testing, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy; the flame retardation of the ceramifiable flame-retardant EVA composites was studied with the aid of vertical burning testing (UL-94), limiting oxygen index (LOI), and cone calorimeter (CC) tests. The results showed that the ceramics were prepared successfully at different high temperatures based on the ceramifiable flame-retardant polymer composites. For the EVA/GD/GF/OMMT/MCA system with a weight ratio of 35/26/9/5/25, the ceramic formed at 800 °C had a flexural strength of 13.82 MPa, and both a UL-94 V-0 rating and a LOI of 28.2% were achieved. Moreover, CC results confirmed that the heat release rate (HRR), total release rate (THR), smoke production rate (SPR), and mass loss rate (MLR) of the composite were reduced significantly compared with the corresponding value of neat EVA or the ceramifiable EVA composite without MCA. The dilatometric experiment analysis, SEM, and viscosity analysis demonstrated that a eutectic mixture resulting from GD and GF led to the formation of ceramics at high temperature. Thermal gravimetric analysis (TG), etc. illustrated that both the release of a large amount of non-flammable gas and the presence of OMMT led to the much better flame retardancy of EVA/GD/GF/OMMT/MCA than that of neat EVA or the ceramifiable EVA composites without MCA.
Co-reporter:Ya-Hui Guan, Jian-Qian Huang, Jun-Chi Yang, Zhu-Bao Shao, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 13) pp:3524-3531
Publication Date(Web):March 31, 2015
DOI:10.1021/acs.iecr.5b00123
Biocomposite of wood flour (WF)/polypropylene (PP) composite (WPC) is not easily flame-retarded because of the different flame retardant mechanisms of PP and WF. In order to improve the flame retardancy of WPC, a single flame retardant of ammonium polyphosphate (APP) modified via ion exchange reaction with ethanolamine, which is named as ETA-APP, was used to prepare flame-retardant WPC. The flammability was investigated by limiting oxygen index (LOI), UL-94 vertical burning test, and cone calorimeter. The results show the flame retardant properties of the flame-retardant WPC are improved greatly. The limiting oxygen index is 43.0%, which is increased by 71.6% compared with that of WPC with the same content of APP. And the vertical burning test can pass UL-94 V-0 rating. The results of cone calorimeter test show that the heat release rate (HRR) and total heat release (THR) of the WPC with ETA-APP are decreased in comparison with WPC/APP. The flame-retardant mechanism of WPC/ETA-APP system was investigated by thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). It is found that the hydroamine groups and phosphate acid in ETA-APP might promote the etherification and dehydration reactions in WPC/ETA-APP, which facilitated the formation of stabile char residue of WPC. Consequently, the flame-retardant efficiency is improved greatly. The flexural properties of WPC/30 wt % ETA-APP increase a lot in comparison with WPC/30 wt % APP, which is because of the better compatibility of ETA-APP with WF.
Co-reporter:Shao-Long Li, Fang Wu, Yu-Zhong Wang, and Jian-Bing Zeng
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 24) pp:6258-6268
Publication Date(Web):June 4, 2015
DOI:10.1021/acs.iecr.5b00637
In this study, a series of biobased and biodegradable thermoplastic poly(ester urethane)s (PEUs) with different compositions were synthesized via chain extension reaction of dihydroxyl terminated poly(propylene succinate) (HO-PPS-OH) and poly(butylene succinate) (HO-PBS-OH) with 4,4′-methylenediphenyl diisocyanate (MDI) as a chain extender. The thermal behaviors of PEUs were characterized by differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). All the PEUs showed a single glass transition temperature shifting with compositions; only one melting peak was observed when the feeding weight ratio of PPS to PBS was less than 8:2, and the crystallization ability of the PEUs decreased gradually with the increase in PPS content. The tensile and tensile hysteresis tests suggest that the PEUs showed the tensile behaviors of elastomers when the weight ratios of PPS/PBS were 7/3, 6/4, and 5/5, and the tensile hysteresis value and Young’s modulus increased with increase in PBS content. The tensile strength and elongation at break of the three PEU elasomers exceeded 37 MPa and 1600%. Enzymatic (Candida rugosa lipase) hydrolysis study showed that the degradation rate increased with PPS fraction, according to the weight loss measurement and scanning electron microscopy observations.
Co-reporter:Rui-Min Li, Cong Deng, Cheng-Liang Deng, Liang-Ping Dong, Hong-Wei Di and Yu-Zhong Wang
RSC Advances 2015 vol. 5(Issue 21) pp:16328-16339
Publication Date(Web):29 Jan 2015
DOI:10.1039/C4RA15971C
To improve simultaneously the water resistance, flame retardancy and mechanical properties of an polyethylene-octene elastomer (POE) composite containing ammonium polyphosphate (APP), an effective method was developed, in which the APP was first coated by a silicon compound with a vinyl group, and then introduced into the POE matrix through chemical cross-linking. X-ray protoelectron spectroscopy (XPS) etc. measurements confirmed that the coated APP (CAPP) was prepared successfully. Then, together with a charring agent (CA), CAPP was used to flame retard POE. The combustible performance of the POE composites was investigated by limiting oxygen index (LOI), vertical burning (UL-94), and cone calorimeter (CC) tests. The results showed that the POE composite containing 22.5 wt% CAPP had better flame retardancy than POE containing equal amounts of APP, especially the CAPP system had much lower heat release rate (HRR), total heat release (THR), smoke production rate (SPR), and mass loss rate (MLR) than the APP system with the same amount of flame retardant. Furthermore, the CAPP system passed the UL-94 V-0 rating after water treatment at 70 °C for 7 days; while the APP system did not. Thermal gravimetric analysis (TGA), XPS, etc. measurements demonstrated that the formation of a rich residue containing Si–C, Si–O–C, etc. structures in the residue of the CAPP system should be the most important reason for its better flame retardancy than that of the APP system. Mechanical tests illustrated that the CAPP system had higher tensile strength and elongation at break than the APP system at the same condition, which should be due to the good interfacial adhesion resulting from the existence of silicon compounds at the surfaces of APP and its cross-linking with the POE matrix. All these results illustrate that it should be an efficient method to simultaneously improve the water resistance, flame retardancy and mechanical properties of a POE composite containing APP through functionalizing the APP and then chemically incorporating it into the polymer matrix.
Co-reporter:Chen Zhu, Cong Deng, Jing-Yu Cao, Yu-Zhong Wang
Polymer Degradation and Stability 2015 Volume 121() pp:42-50
Publication Date(Web):November 2015
DOI:10.1016/j.polymdegradstab.2015.08.008
An efficient flame retardant poly[N,N,N′,N′,N″,N″-hexakis-cyclotriphosphazene-[1,3,5]triazine- 2,4,6-triamine] (HPTT) was synthesized in this work, and used to flame retard silicone rubber (SR). The flame retardancy of SR/HPTT was investigated by limiting oxygen index (LOI), vertical burning test (UL-94), and cone calorimetry. At 18 wt% HPTT, the SR/HPTT composite achieved a LOI value of 31.8% and UL-94 V-0 rating, and the heat release rate (HRR), the peak of heat release rate (PHRR), and smoke production rate (SPR) were significantly reduced compared those of (neat) SR. All the flame retardation tests indicate that the flame retardancy of SR was greatly improved after incorporating 18 wt% HPTT. The flame-retardant mechanism of HPTT was investigated by thermogravimetric analysis (TGA), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). TGA results showed the residue of SR/HPTT was much higher than that of SR. SEM observation showed that the inner residue of SR/HPTT was more compact than that of SR. XPS further demonstrated that the Si–C, C–C, etc. structures were formed in the residue of SR/HPTT. The compact and stable char layer formed at the inner layer of the residue during thermal decomposition must be the leading reason for the excellent flame retardancy of SR/HPTT.
Co-reporter:Shao-Long Li;Fang Wu;Yang Yang;Jian-Bing Zeng
Polymers for Advanced Technologies 2015 Volume 26( Issue 8) pp:1003-1013
Publication Date(Web):
DOI:10.1002/pat.3519
In order to modify the properties of poly(butylene succinate), poly(diethylene glycol succinate) (PDGS) segment was incorporated by chain-extension reaction of dihydroxyl-terminated PBS and PDGS precursors using hexamethylene diisocyanate as a chain extender to form PBS-b-PDGS multiblock copolymers. The chemical structure and basic physical properties of the multiblock copolyesters were characterized by nuclear magnetic resonance spectroscopy, differential scanning calorimeter (DSC), wide angle X-ray diffraction, and tensile testing. The results suggested that the incorporation of PDGS segments would increase the elongation at break of PBS significantly while decrease its melting temperature and crystallization temperature slightly. The isothermal crystallization kinetics studied by DSC and polarized optical microscopy indicated that the crystallization rate of the multiblock polymers decreased gradually with increasing PDGS segment content while the crystallization mechanism kept unchanged and the spherulitic growth rate of the multiblock copolymers decreased gradually with increase in PDGS content due to its diluent effect to the crystallization of PBS segments. Copyright © 2015 John Wiley & Sons, Ltd.
Co-reporter:Ling Lin;Cong Deng
Polymers for Advanced Technologies 2015 Volume 26( Issue 10) pp:1247-1258
Publication Date(Web):
DOI:10.1002/pat.3560
The influences of both the molecular structure and the melt viscosity differences between Poly(lactic acid) (PLA) and polycarbonate (PC) on the interpenetration of molecular chains at the interface were investigated by comparing the dynamic mechanical properties and morphologies of the as-prepared PLA/PC solution-casting blends with those of their corresponding annealed (180°C, 8 h) samples or PLA/PC melt blends. Additionally, two chain extenders containing epoxy groups (ADR and TGDDM) were used to improve the interfacial strength. Subsequently, the interpenetration of PLA and PC molecular chains at the interface was also surveyed. Finally, the effects of the morphology formed by after adding ADR or TGDDM on the impact property, and heat resistance were discussed. The results showed that there was no interpenetration of molecular chains at the interface in PLA/PC melt blends because of the serious hindrance of the molecular structure and the melt viscosity differences. Although the interfacial strength achieved significant increase after adding ADR or TGDDM, the increase of the interfacial strength should be caused by the connection of ADR or TGDDM molecules with PLA and PC molecules at the interface through chemical bonds rather than the entanglements of PLA and PC molecular chains because of no interpenetration of PLA and PC molecular chains at the interface. Thus, the morphology formed after adding ADR or TGDDM is still the type of complete phase separation, which may be the most suitable morphology for achieving high impact and heat resistance PLA/PC blends because these two properties strongly depend on the crystallinity of PLA phase. Copyright © 2015 John Wiley & Sons, Ltd.
Co-reporter:Liang Lv, Fang Wu, Si-Chong Chen, Yu-Zhong Wang, Jian-Bing Zeng
Polymer 2015 Volume 66() pp:148-159
Publication Date(Web):1 June 2015
DOI:10.1016/j.polymer.2015.04.029
•Ionic group distribution of PBSI could be controlled through chain extension reaction.•The morphology of PBSI was determined by its ionic group distribution.•The physical properties of PBSI depend strongly on its ionic group distribution.Dihydroxyl terminated poly(butylene succinate) ionomer precursors (Pre-PBSIs) with different ionic group contents were prepared to chain-extend with dihydroxyl terminated poly(butylene succinate) to synthesize high molecular weight poly(butylene succinate) ionomers (PBSIs) with controlled ionic group distributions. The chemical structures and molecular weights of the precursors and PBSIs were characterized by nuclear magnetic resonance spectroscopy and gel permeation chromatography. The effect of ionic group distribution on the morphology, thermal behavior, isothermal crystallization kinetics, rheological behavior, and mechanical properties of PBSIs were investigated by transmission electron microscopy (TEM), differential scanning calorimeter (DSC), polarizing optical microscopy (POM), wide angle X-ray diffraction (WAXD), rotational rheometer, and tensile testing. With the increase of ionic group content in incorporated Pre-PBSI, phase separation between PBSI and PBS segments occurred as observed by TEM, the crystallization was improved as investigated by DSC and WAXD, while the complex viscosity and tensile strength decreased as studied by rotational rheometer and tensile testing. All the results indicated that the properties of PBSI can be regulated by the ionic group distribution.
Co-reporter:Yi Zhang, Yan-Peng Ni, Ming-Xin He, Xiu-Li Wang, Li Chen, Yu-Zhong Wang
Polymer 2015 60() pp: 50-61
Publication Date(Web):
DOI:10.1016/j.polymer.2015.01.030
Co-reporter:Gang Wu, Si-Chong Chen, Chang-Lei Liu, and Yu-Zhong Wang
ACS Nano 2015 Volume 9(Issue 4) pp:4649
Publication Date(Web):April 10, 2015
DOI:10.1021/acsnano.5b01370
It is extremely important for emerging applications and still enormously challenging to develop multifunctional stimuli-responsive anisotropic polymeric micelles with integration of potentially targeted therapeutic and diagnostic function. Herein, we report a first example of fluorescent anisotropic micelles (FAMs) with Fe3+, DTT, H2O2, and thermal responsive fluorescence and morphology. FAMs from direct aqueous self-assembly of amphiphilic diblock copolymer showed reversible “switch off/on” of aqua fluorescent emission and controllable structural change by sequential addition of Fe3+ and DTT. In addition, the FAMs had reversible dual-thermal responsiveness of fluorescence and morphology. This micelle could serve as a promising candidate for all-in-one application of quantitative detecting, imaging, drug delivery, and targeted release.Keywords: block copolymers; fluorescent; micelles; self-assembly; shape anisotropy; stimuli-responsive;
Co-reporter:De-Ming Guo, Teng Fu, Chao Ruan, Xiu-Li Wang, Li Chen, Yu-Zhong Wang
Polymer 2015 Volume 77() pp:21-31
Publication Date(Web):23 October 2015
DOI:10.1016/j.polymer.2015.09.016
•The arylene-ether containing unit is introduced into PET main-chain.•The arylene-ether units improved the copolyester's thermal stability and char residue.•The arylene-ether units form conjugated heteroaromatic structures via rearrangement.•The heteroaromatic structures endow copolyesters with good flame retardant performance.•These copolyesers show low smoke release and anti-dripping behaviors.In order to avoid the serious melt-dripping problems caused by conventional phosphorus flame retardants, a new arylene-ether containing monomer named 2,2′-(4,4′-(1,4-phenylenebis(oxy))bis(4,1-phenylene))bis(oxy) diethanol (PBPBD) was synthesized and introduced into the PET main-chain via condensation polymerization. With the incorporation of arylene-ether units, the thermal stability and the char residue from combustion of flame-retardant-element-free copolyesters containing PBPBD (BDxPETs) increased dramatically. However, the crystallinity and melting temperature of these copolymers were lower than the same quantities for PET. Thermal degradation kinetic was investigated using the Ozawa-Flynn-Wall method, which illustrated that the apparent activation energy for decomposition of the copolyesters was enhanced with increasing the conversion and the content of PBPBD. Py-GC/MS results showed that the PBBPD structural units undergo rearrangement reactions at high temperature, and ultimately form conjugated heteroaromatic structures, which lead to the formation of stable char residues with unique “stick-shaped” micro-morphology. Due to these rearrangement reactions, BDxPETs showed an expected flame retardant performance and a reduction in smoke generation during combustion. For example, the LOI value for BD10PET was 28.4, and the total smoke production (TSP) was 10.4 m2, much smaller than that for PET, 18.8 m2. Moreover, melt-dripping was restricted.
Co-reporter:Shuang-lan Du;Xue-bao Lin;Rong-kun Jian
Chinese Journal of Polymer Science 2015 Volume 33( Issue 1) pp:84-94
Publication Date(Web):2015 January
DOI:10.1007/s10118-015-1560-z
In this work, a flame-retardant polypropylene (PP)/ramie fiber (RF) composite was prepared. The ramie fibers were wrapped chemically by a phosphorus- and nitrogen-containing flame retardant (FR) produced via in situ condensation reaction so as to suppress their candlewick effect. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) demonstrated that the ramie fibers wrapped chemically by FR (FR-RF) were obtained successfully. Thermogravimatric test showed that the PP/FR-RF composite had more residue and better thermal stability at high temperatures than the PP/RF composite. Cone calorimeter (CC) results indicated that the peak of heat release rate (PHRR) and total heat release (THR) correspondingly decreased by 23.4% and 12.5% compared with the values of neat PP/RF. The PP/FR-RF composite created a continuous and compact char layer after the combustion. Combining FTIR analysis of char residue after CC test with heat conduction coefficient results, it could be concluded that the charring of FR on RF greatly weakened the candlewick effect of RF, and more char residue in the RF domain facilitated the formation of more continuous and compact char layer in the whole combustion zone, consequently protected PP composites during combustion, resulting in the better flame retardancy of PP/FR-RF composite than that of PP/RF composite.
Co-reporter:Cheng-liang Deng;Cong Deng 邓聪;Jing Zhao;Rui-min Li
Chinese Journal of Polymer Science 2015 Volume 33( Issue 2) pp:203-214
Publication Date(Web):2015 February
DOI:10.1007/s10118-015-1575-5
To improve the flame-retardant efficiency and water resistance of ammonium polyphosphate (APP), the UV-curable pentaerythritol triacrylate (PETA) was used to microencapsulate APP via the UV curing polymerization method. The prepared PETA-microencapsulated APP (PETA-APP) was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric (TG) analysis. PETA-APP was used as intumescent flame retardant (IFR) alone to flame retard polypropylene (PP). The water resistance of PP/PETA-APP composites was investigated, and the effect of PETA on the combustion behaviors of PP/APP composites was studied through limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter (CC) test, respectively. With 40 wt% of PETA-APP, the PP/PETA-APP system could achieve a LOI value of 30.0% and UL-94 V-0 rating after treatment in hot water for 168 h, while the LOI value of the system containing 40 wt% uncoated APP was only 19.2%, and it failed to pass the UL-94 rating. CC test results showed that the heat release rate (HRR), mass loss rate (MLR) and smoke production rate (SPR) of PP/PETA-APP system decreased significantly compared with PP/APP system, especially the peak of HRR was decreased by 51.4%. The mechanism for the improvement of flame reatardancy for PP/PETA-APP composites was discussed based on FTIR and X-ray photoelectron spectroscopy (XPS) tests. All these results illustrated that simultaneous improvement of flame retardancy and water resistance for PP/APP was achieved through coating UV-curable PETA onto APP.
Co-reporter:Zhu-Bao Shao, Cong Deng, Yi Tan, Li Yu, Ming-Jun Chen, Li Chen and Yu-Zhong Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 34) pp:13955-13965
Publication Date(Web):01 Jul 2014
DOI:10.1039/C4TA02778G
Ammonium polyphosphate (APP) is not an efficient flame retardant for polypropylene (PP) when it is used alone. In order to improve its flame-retardant efficiency, ethanolamine (ETA) was used to chemically modify APP via ion exchange reaction. The resulting ethanolamine-modified ammonium polyphosphate (ETA-APP) was alone applied to flame retard PP, the limiting oxygen index (LOI) value could reach 35.0% and the vertical burning test (UL-94) could pass the V-0 rating at a loading of 35 wt% ETA-APP. Moreover, cone calorimeter (CC) test results showed that the heat release rate (HRR), the total heat release (THR), the mass loss rate (MLR), the smoke production rate (SPR) and the total smoke production (TSP) of PP/35 wt% ETA-APP composite largely decreased, for example, by 77.2%, 88.5% and 77.9% for THR, TSP and the fire growth rate (FGR), respectively, compared with PP containing an equal amount of APP. In addition, the residual char of PP/35 wt% ETA-APP increased by 195.6% compared with that of PP/35 wt% APP. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the flame retardant mechanism of ETA-APP. It was confirmed that the formation of P–O–C and P–N–C structures, resulting from the incorporation of ETA could greatly improve the stability of intumescent char layer and consequently lead to the much better flame retardancy of ETA-APP than that of unmodified APP. Experimental results demonstrated that the prepared ETA-APP acted not only as the acid source and blowing source as efficient as unmodified APP, but also as an excellent charring agent beyond the unmodified APP.
Co-reporter:Rong Yang, Li Chen, Chao Ruan, Hai-Yi Zhong and Yu-Zhong Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 30) pp:6155-6164
Publication Date(Web):28 May 2014
DOI:10.1039/C4TC00512K
A series of main-chain thermotropic liquid crystalline polyesters were synthesized by polycondensation from mesogenic dial such as 4,4′-bis(6-hydroxyhexyloxy)biphenyl (BHHBP) and various diacids with different substituents such as succinic acid (no side group), 2-methylsuccinic acid (aliphatic side group) and 2-phenylsuccinic acid (aromatic side group), named poly(4,4′-bis(6-hydroxyhexyloxy)biphenyl succinate) (PBDS), poly(4,4′-bis(6-hydroxyhexyloxy)biphenyl methylsuccinate) (PBDMS), and poly(4,4′-bis(6-hydroxyhexyloxy)biphenyl phenylsuccinate) (PBDPS), respectively. Liquid crystalline behaviours were investigated through differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and small angle X-ray scattering (SAXS) and the thermal stability of the polyesters was determined via thermogravimetric analysis (TGA). PBDS, PBDMS and PBDPS showed a SmF, SmB and SmA phase, respectively. On enlarging the side group, the d-spacing of the smectic layer increased, indicating folding packing of the polymer chains. Therefore, the adjacent phenyl rings in side groups stacked well together and formed strong π–π interactions even when the temperature was higher than Ti. The special structure of PBDPS could provide good mechanical properties. Thus, PBDPS exhibited the maximum tensile stress (28.6 MPa) and the highest elongation at break (1060%). Furthermore, the strong π–π interaction can act as netpoints; therefore, PBDPS exhibited excellent shape fixing (>99%) and shape recovery ratio (>99%) with large strain (>220%).
Co-reporter:Hong-Bing Chen, Yu-Zhong Wang, and David A. Schiraldi
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 9) pp:6790
Publication Date(Web):April 14, 2014
DOI:10.1021/am500583x
Poly(vinyl alcohol) (PVOH)-based aerogel composites with nanoscale silica, halloysite, montmorillonite (MMT), and laponite were prepared via a freeze-drying method. The PVOH/MMT and PVOH/laponite composites exhibit higher compressive moduli than the PVOH/SiO2 or PVOH/halloysite samples. Layered microstructures were observed for the samples except with PVOH/laponite, which showed irregular network morphologies. Thermogravimetric analysis of the aerogel samples showed increased thermal stability with the addition of nanofillers. The heat release measured by cone calorimetry, smoke release, and carbon monoxide production of the aerogel composites are all significantly decreased with the addition of nanofillers; these values are much lower than those for commercial expanded polystyrene foam. The fillers did not lead to obvious increases in the limiting oxygen index values, and the corresponding time to ignition values decrease. The ability to adjust the nanofiller levels in these foamlike aerogel composites allows for specific tuning of these products for fire safety.Keywords: aerogel; flammability; poly(vinyl alcohol);
Co-reporter:Zhu-Bao Shao, Cong Deng, Yi Tan, Ming-Jun Chen, Li Chen, and Yu-Zhong Wang
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 10) pp:7363
Publication Date(Web):April 17, 2014
DOI:10.1021/am500789q
We found in our previous study that ethylenediamine- or ethanolamine-modified ammonium polyphosphates could be used alone as an intumescent flame retardant for polypropylene (PP), but their flame-retardant efficiency was not very high. In this present work, a novel highly-efficient mono-component polymeric intumescent flame retardant, piperazine-modified ammonium polyphosphate (PA-APP) was prepared. The oxygen index value of PP containing 22 wt % of PA-APP reached 31.2%, which increased by 58.4% compared with that of PP with equal amount of APP, and the vertical burning test (UL-94) could pass V-0 rating. Cone calorimeter (CC) results indicated that PP/PA-APP composite exhibited superior performance compared with PP/APP composite. For PP containing 25 wt % of PA-APP, fire growth rate (FGR) and smoke production rate (SPR) peak were reduced by 86.4% and 78.2%, respectively, compared with PP blended with 25 wt % APP. The relevant flame-retardant mechanism of PA-APP was investigated by Fourier transform infrared spectroscopy etc. The P–N–C structure with the alicyclic amine was formed during the thermal decomposition of piperazine salt (−NH2+–O–P−), and the rich P–N–C structure facilitated the formation of stable char layer at the later stage, consequently improving the flame-retardant efficiency of APP.Keywords: ammonium polyphosphate; flame retardant; piperazine; polypropylene;
Co-reporter:Guang-Chen Liu, Yi-Song He, Jian-Bing Zeng, Yao Xu and Yu-Zhong Wang
Polymer Chemistry 2014 vol. 5(Issue 7) pp:2530-2539
Publication Date(Web):17 Dec 2013
DOI:10.1039/C3PY01649H
Polylactide (PLA), a biobased polymer, has a short elongation at break and low impact strength, which restricted its broad application as a commodity polymer. In this paper, super-tough polylactide/crosslinked polyurethane (PLA/CPU) binary blends with CPU dispersed in the PLA matrix were prepared by reactive blending of PLA with poly(ethylene glycol) (PEG) and polymeric methylene diphenylene diisocyanate (PMDI). The in situ polymerization of PEG and PMDI in the PLA matrix formed CPU, and the interfacial compatibilization between PLA and CPU phases occurred by the reaction of NCO groups with terminal hydroxyl groups of PLA, which was confirmed by Fourier transform infrared spectroscopy. The results of a tensile test and a notched Izod impact test suggest that the elongation at break and impact strength were increased to more than 20 and 30 times those of neat PLA, respectively. The effects of PEG molecular weight (namely soft segment length of CPU) and CPU content on the phase morphology and impact strength of PLA/CPU blends were investigated systematically. The optimum CPU particle size for high impact toughness was identified to be 0.7–1.0 μm when the soft segment length and the content of CPU were in the ranges of 1000–2000 g mol−1 and 20–30 wt%, respectively. The compatibility between the dispersed CPU and PLA matrix was studied by dynamic mechanical analysis through the change in glass transition temperatures of PLA and CPU components. The results suggest that the compatibility increased with increasing soft segment length and content of CPU, which was mainly due to the increased plasticization effect. With improved toughness, the PLA/CPU blends could be used as substitutes for some traditional petroleum-based polymers.
Co-reporter:Yi Zhang, Li Chen, Jing-Jing Zhao, Hong-Bing Chen, Ming-Xin He, Yan-Peng Ni, Jun-Qiu Zhai, Xiu-Li Wang and Yu-Zhong Wang
Polymer Chemistry 2014 vol. 5(Issue 6) pp:1982-1991
Publication Date(Web):15 Nov 2013
DOI:10.1039/C3PY01030A
In this study, a novel phosphorus-containing ionic monomer, named sodium salt of 10H-phenoxaphosphine-2,8-dicarboxylic acid,10-hydroxy-,2,8-dihydroxyethyl ester,10-oxide (DHPPO-Na), was synthesized, characterized, and then copolymerized to prepare poly(ethylene terephthalate)-based ionomers. The chemical structure of the resulting ionomers was confirmed by 1H, 13C, and 31P NMR spectroscopy. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to investigate the thermal properties of the ionomers. Compared with that of neat PET, the initial decomposition temperature of PETIs decreased in a nitrogen atmosphere while it increased in air. The crystallinity of PETIs was enhanced firstly and then destroyed with the ionic group increase. The limiting oxygen index (LOI) test and cone calorimeter were used to characterize the flame-retardant properties of the ionomers. The results showed that the introduction of DHPPO-Na could endow an expected flame-retardant performance, meanwhile it considerably restricted the melt-dripping behavior and suppressed the smoke release. The rheology test confirmed that the ionic groups increased the melt viscosity via ionic aggregation during heating, which was a benefit for the flame-retardant property of the copolyester.
Co-reporter:Li Chen, Chao Ruan, Rong Yang and Yu-Zhong Wang
Polymer Chemistry 2014 vol. 5(Issue 12) pp:3737-3749
Publication Date(Web):29 Jan 2014
DOI:10.1039/C3PY01717F
The flame retardation of polymeric materials can be achieved by addition of small-molecule flame retardants. However, traditional small molecule flame retardants exhibit practical drawbacks during application, such as migration problems, the deterioration of polymer performance, as well as potential persistence, bio-accumulation and toxicity (PBT), etc. High molecular weight molecules have been found to be less accessible by living organisms and so have an automatically lower PBT profiles than small molecules. Phosphorus-containing thermotropic liquid crystalline polymers have proven to be a class of efficient polymeric flame retardants, which can overcome the aforementioned drawbacks of small molecules and have potential industrial applications to replace some of the existing small molecule flame retardants. The recent relevant developments are reviewed in this article.
Co-reporter:Chang-Lei Liu;Mei-Jia Wang;Gang Wu;Jiao You;Si-Chong Chen;Ya Liu
Macromolecular Rapid Communications 2014 Volume 35( Issue 16) pp:1450-1457
Publication Date(Web):
DOI:10.1002/marc.201400261
Co-reporter:Shao-Long Li, Jian-Bing Zeng, Fang Wu, Yang Yang, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 4) pp:1404-1414
Publication Date(Web):January 3, 2014
DOI:10.1021/ie402499t
Biodegradable thermoplastic poly(ester urethane) (PEU) elastomers containing poly(diethylene glycol succinate) (PDGS) and poly(butylene succinate) (PBS) were synthesized by chain extension of dihydroxyl terminated PDGS and PBS precursors with 4,4′-methylenediphenyl diisocyanate as a chain extender. The structure, molecular weight, and physical properties of the PEUs were investigated by 1H NMR, GPC, DSC, WAXD, DMA, and tensile tests. The results suggest that the compositions affect the physical properties more significantly than the segment lengths. The PEU containing 28.2 wt % PBS showed the best mechanical properties with ultimate strength and elongation at break of 41 MPa and 1503%, respectively. Both the storage modulus and Young’s modulus increased significantly with increasing PBS segment content, which was reasonably ascribed to the increasing degree of crystallinity. The hysteresis value increased with PBS segment content while it decreased slightly with lengths of both hard and soft segments, which were also attributed to the different crystallization behaviors of the PEUs.
Co-reporter:Yuan-Wei Yan, Jian-Qian Huang, Ya-Hui Guan, Ke Shang, Rong-Kun Jian, Yu-Zhong Wang
Polymer Degradation and Stability 2014 Volume 99() pp:35-42
Publication Date(Web):January 2014
DOI:10.1016/j.polymdegradstab.2013.12.014
A phosphorus-containing inorganic compound, aluminum hypophosphite (AP), was used to prepare flame-retardant polystyrene (PS). The flammability of the PS/AP composites was investigated by the limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter test. When the content of AP reaches 25 wt%, the LOI of PS/AP is 25.6% and it passes UL-94 V-0 rating. The results of cone calorimeter test show that the heat release rate (HRR), the total heat release (THR) and the mass loss rate (MLR) of PS/AP composites are significantly reduced. The thermal degradation mechanism of PS/AP was investigated by thermogravimetric analysis (TGA), Fourier transform infrared spectrometry (FTIR), thermal gravimetric-Fourier transform infrared spectrometry (TG-FTIR), pyrolysis gas chromatography-mass spectrometry (Py-GC/MS), and X-ray photoelectron analysis (XPS) tests. The results indicate that PS/AP has a combined gas-phase and condensed-phase activity in the combustion and degradation of the composites. Consequently, a possible flame-retardant mechanism of PS/AP composites is proposed.
Co-reporter:Rong-Kun Jian, Li Chen, Si-Yang Chen, Jia-Wei Long, Yu-Zhong Wang
Polymer Degradation and Stability 2014 Volume 109() pp:184-193
Publication Date(Web):November 2014
DOI:10.1016/j.polymdegradstab.2014.07.018
Aluminum isobutylphosphinate (APBu) and its synergistic system with red phosphorus (APBu/RP) were used to flame-retard ABS. With the addition of APBu to ABS, the flame retardance of the material was greatly improved, that LOI value was as high as 29.8%, and a UL-94 V-0 rating was obtained; moreover, heat release parameters obtained from cone calorimetry decreased. However, the smoke release of the material during combustion increased. When RP was added to ABS-APBu system, flame-retardant synergism was gained, and it was helpful to reduce the smoke release of the material. The decomposition behaviors of materials were studied by thermogravimetric analysis (TG), and it was found that the residues of materials at 700 °C increased with the addition of APBu or APBu/RP. The flame-retardant mechanisms of APBu and APBu/RP were analyzed by Fourier transform infrared spectrum (FTIR), scanning electron microscopy (SEM) and pyrolysis-gas chromatograph/mass spectrometer (Py-GC/MS). Results suggested that the addition of RP to ABS-APBu further enhanced the flame retardation of APBu both in the gaseous phase and condensed phase, leading to a high synergistic effect.
Co-reporter:Li Yu, Li Chen, Liang-Ping Dong, Liang-Jie Li and Yu-Zhong Wang
RSC Advances 2014 vol. 4(Issue 34) pp:17812-17821
Publication Date(Web):31 Mar 2014
DOI:10.1039/C4RA00700J
A novel organic–inorganic hybrid flame retardant (DOPA–ATH), which was prepared via reacting dibenzo[c,e][1,2]oxaphosphinic acid (DOPA) with aluminum trihydroxide (ATH), was incorporated in ethylene-vinyl acetate copolymer (EVA) to improve its flame retardance. The structure, morphology and thermal stability of the hybrid flame retardant were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results suggested that DOPA was grafted onto ATH successfully, therefore resulting in higher thermostability than ATH. The flame retardance and burning behaviour of EVA with DOPA–ATH were also studied using limiting oxygen index (LOI), Underwriter laboratory 94 vertical burning test (UL-94 V) and cone calorimeter test (CCT). Results of UL-94 tests and LOI tests showed that the flame retardance of EVA/DOPA–ATH was better than EVA/ATH binary and EVA/DOPA/ATH ternary flame-retardant composites. The data obtained from the CCT showed that the peak heat release rate (PHRR) of EVA with the addition of 50 wt% DOPA–ATH was reduced by about 25% comparing with EVA with equivalent ATH. Total heat release (THR) and total smoke production (TSP) were reduced remarkably as well. The thermogravimetric analysis (TGA) data showed that the thermal stability of EVA/DOPA–ATH was improved with increased initial decomposition temperature and char residue. SEM observations of cryogenically fractured and tension fractured surfaces showed that EVA/DOPA–ATH had better interfacial interaction comparing with those of EVA/ATH and EVA/DOPA/ATH, which resulted in better elongation at break and tensile strength.
Co-reporter:Rong-Kun Jian, Li Chen, Bin Zhao, Yuan-Wei Yan, Xiao-Fan Li, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 6) pp:2299-2307
Publication Date(Web):January 20, 2014
DOI:10.1021/ie403726m
Three metal hypophosphites, including aluminum hypophosphite (AP), magnesium hypophosphite (MP), and calcium hypophosphite (CP), were applied to flame retard acrylonitrile–butadiene–styrene (ABS). Thermal stability of three flame-retardant ABS were evaluated, and the enhancement of thermal stability were found. Flammable properties of flame-retardant ABS were investigated by Underwriters Laboratories 94 vertical burning test (UL-94), limit oxygen index (LOI), and cone calorimetry. Results suggested that AP could endow the best flame retardance for ABS with a UL-94 V-0 rating and LOI value of 25.1%. The peak heat release rate of ABS-AP reduced to 174.8 kW/m2, and the total heat released was decreased to 40.9 MJ/m2. Thermogravimetric Fourier transform infrared (TG-FTIR), FTIR, and scanning electron microcsopy–energy-dispersive X-ray spectrometry (SEM-EDX) were used to characterize the gaseous products and condensed residue respectively. Results showed that the flame-retardant mechanism was attributed to the formation of a two-layer protective barrier consisting of an organic P–O–C char layer and an inorganic layer to insulate material from fire and oxygen in the condensed phase, and the generation of P• and PO• to capture the reactive radicals in the vapor phase.
Co-reporter:Ming-Jun Chen, Chun-Rong Chen, Yi Tan, Jian-Qian Huang, Xiu-Li Wang, Li Chen, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 3) pp:1160-1171
Publication Date(Web):December 27, 2013
DOI:10.1021/ie4036753
A halogen-free phosphorus-containing triol named phosphoryltrimethanol (PTMA) was synthesized and used as a cross-linking agent and a reactive-type flame retardant to prepare inherently flame-retardant flexible polyurethane foam (FPUF). Incorporation of a low content (7.8 wt %) of PTMA into the polyurethane chains can increase the flame retardance of FPUF because of good char formation. The residual chars and evolved gases of PTMA-cross-linked FPUFs were analyzed by SEM, FTIR spectroscopy, inductively coupled plasma-atomic emission spectrometry (ICP-AES), energy-dispersive X-ray (EDX) spectroscopy, and thermogravimetric analysis (TGA) coupled with FTIR spectroscopy. The results indicated that more than 60% of the phosphorus in PTMA-cross-linked FPUF was decomposed into polyphosphoric acid or its derivatives and retained in the char residue. This shows that PTMA mainly played a role in the condensed phase of flame-retardant FPUF. Based on the results, a possible thermal degradation mechanism of PTMA-cross-linked FPUF is proposed.
Co-reporter:Hong-Zhen Li, Si-Chong Chen, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 44) pp:17355-17361
Publication Date(Web):2017-2-22
DOI:10.1021/ie502531w
A novel plasticizer (lacti-glyceride) synthesized by esterification of glycerol with l-lactic acid was developed for thermal processing of PVA/PLA blend. Meanwhile, the stannous octoate (Sn(Oct)2) was used as the catalyst for the transesterification reaction of PVA, PLA, and the plasticizer. The results showed that the PVA/PLA blends plasticized with lacti-glyceride have improved thermal processability and mechanical properties compared to those plasticized with glycerol, because the lacti-glyceride may act not only as a plasticizer but also as a compatibilizer for PVA and PLA. SEM images indicated that PVA/PLA blends catalyzed with Sn(Oct)2 had better compatibility than those without catalyst. Water contact angle measurements showed that the PVA/PLA blends plasticized with lacti-glyceride have much more hydrophobic surfaces than those blends plasticized with glycerol. The blends will find wider applications than PVA.
Co-reporter:Fang Wu, Cai-Li Huang, Jian-Bing Zeng, Shao-Long Li and Yu-Zhong Wang
RSC Advances 2014 vol. 4(Issue 97) pp:54175-54186
Publication Date(Web):24 Sep 2014
DOI:10.1039/C4RA05484A
To obtain an excellent comprehensive performance of poly(ethylene succinate) (PES), we have synthesized a series of poly(ethylene succinate) (PES) urethane ionenes (PESUIs) with various content of urethane ionic group by the chain extension reaction of dihydroxyl-terminated poly(ethylene succinate) and diethanolamine hydrochloride with hexamethylene diisocyanate as a chain extender, and we systematically investigated the composition dependence of the physico-chemical properties of PESUI through a series of characteristic techniques. The results of thermal and crystallization behaviors suggest that the incorporation of urethane ionic group slightly affects the glass transition temperature, melting temperature, and thermal stability, and significantly accelerates the crystallization rate of PES without changing the crystallization mechanism. The fastest crystallization rate was reached with the incorporation of 4 mol% urethane ionic groups. Spherulitic morphology observation indicates that nucleation density significantly increased, while spherulitic growth rate gradually decreased with increase in urethane ionic group content. Both complex viscosity and storage modulus initially increased and then decreased with increase in urethane ionic group content, and their maximum values were observed for the sample with 4 mol% of urethane ionic group. Mechanical properties slightly varied with urethane ionic group content.
Co-reporter:Hai-Chun Dang, Wu-Cheng Nie, Xiu-Li Wang, Wen-Tao Wang, Fei Song and Yu-Zhong Wang
RSC Advances 2014 vol. 4(Issue 96) pp:53380-53386
Publication Date(Web):06 Oct 2014
DOI:10.1039/C4RA10465J
Dandelion-like CaCO3 (DCC) was successfully fabricated in the presence of [MMIM][Me2PO4]. [MMIM][Me2PO4] not only acts as a template to control the morphology of CaCO3, but also provides anions to adsorb CO2 in air facilitating the construction of polymorph CaCO3. The incorporation of DCC greatly improves the properties of PCL.
Co-reporter:Yi-Song He, Jian-Bing Zeng, Guang-Chen Liu, Qiu-Tong Li and Yu-Zhong Wang
RSC Advances 2014 vol. 4(Issue 25) pp:12857-12866
Publication Date(Web):24 Feb 2014
DOI:10.1039/C4RA00718B
Super-tough poly(L-lactide)/crosslinked polyurethane (PLLA/CPU) blends with a CPU phase dispersed in the PLLA matrix were prepared by reactive blending of PLLA with poly(ethylene glycol) (PEG), glycerol, and 4,4′-methylenediphenyl diisocyanate (MDI). The gel fraction increased while the swelling ratio decreased with increasing glycerol content. FT-IR analysis suggests that interfacial compatibilization between PLLA and CPU occurred via reaction between the hydroxyl group of PLLA and the isocyanate group of MDI. The elongation at break and notched impact strength of PLLA/CPU blends were increased by up to 38 and 21 times those of neat PLLA. The morphology of PLLA/CPU blends plays an important role in notched impact strength and can be controlled by adjusting the content of glycerol. The size of the dispersed CPU phase increased gradually while the notched impact strength increased first and then decreased with increasing glycerol content. Therefore, the notched impact strength can be easily tailored by the content of glycerol of CPU. The optimum size for high impact strength was found to be ∼0.7 μm, which was obtained for the blends with glycerol content in the range of 5 to 10 wt% on the basis of PEG weight. In addition, the effect of glycerol content on the compatibility and rheological properties of PLLA/CPU blends was also investigated.
Co-reporter:Yue Guan, Hai-Bo Zhao, Lei-Xiao Yu, Si-Chong Chen and Yu-Zhong Wang
RSC Advances 2014 vol. 4(Issue 10) pp:4955-4959
Publication Date(Web):12 Nov 2013
DOI:10.1039/C3RA45461D
We reported here a novel three stimuli sensitive hydrogel that was constructed by the formation of host–guest complexes between poly(N-isopropylacrylamide) (PNIPAM) containing azobenzene groups and cyclodextrin dimers connected by disulfide bonds. The obtained hydrogel gives a smart response to the stimuli of temperature, light, and reduction, manifested in the form of a sol–gel phase transition.
Co-reporter:Zhu-Bao Shao, Cong Deng, Yi Tan, Ming-Jun Chen, Li Chen, Yu-Zhong Wang
Polymer Degradation and Stability 2014 Volume 106() pp:88-96
Publication Date(Web):August 2014
DOI:10.1016/j.polymdegradstab.2013.10.005
Ammonium polyphosphate (form I APP) was modified via ion exchange reaction with ethylenediamine, and the resulting modified ammonium polyphosphate (MAPP) was used alone to prepare intumescent flame-retardant (IFR) polypropylene (PP) via melt blending. The flame retardancy of PP containing MAPP was investigated by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter (CC). The LOI value of PP containing 40 wt% of MAPP reached 32.5%, which increased by 56.9% compared with that of PP with the same content of APP, and the UL-94 rating was V-0 in the case of specimen thickness of 1.6 mm, while the latter had no rating. CC test results showed that the heat release rate (HRR), the mass loss rate (MLR) and the smoke production rate (SPR）of PP/MAPP system decreased significantly compared with neat PP and PP/APP systems. Especially the fire growth rate (FGR) and SPR peak of PP containing 35 wt% MAPP decreased by 89.1% and 63.2% respectively compared with those of PP containing 35 wt% APP. These results demonstrated that only by incorporating the MAPP without additional charring agents, could PP be successfully flame retarded. Fourier transform infrared spectroscopy (FTIR) etc. were used to investigate the flame retardant mechanism of MAPP, and it was found that both the generation of carbon–carbon double bonds after the scission of C–N bonds and the residue consisting of some stable structures such as P–N–C and C–N etc. caused the charring ability to increase dramatically, which must be the principal reason for the much better flame retardancy of PP/MAPP system without any additional charring agent compared with APP.
Co-reporter:Cong Deng, Jing Zhao, Cheng-Liang Deng, Qiang Lv, Li Chen, Yu-Zhong Wang
Polymer Degradation and Stability 2014 Volume 103() pp:1-10
Publication Date(Web):May 2014
DOI:10.1016/j.polymdegradstab.2014.03.001
Both MMT synthesized by hydrothermal method (Fe-OMMT) and MMT prepared by modifying MMT using Fe3+ (Fe-MMT) were used to prepare flame-retardant low-density polyethylene (FR-LDPE) together with an intumescent flame retardant (IFR). The effects of two types of MMTs on the flame retardation of FR-LDPE were investigated by different measurements. Combustion tests showed that the limiting oxygen index (LOI) of LDPE/IFR28/Fe-MMT2 was increased to 34.6 from 29 of LDPE/IFR30, and the UL-94 rating of the former reached V-2 from no rating of the latter. Cone calorimeter (CC) test demonstrated that both Fe-OMMT and Fe-MMT improved the combustion behaviors of LDPE/IFR at about 2 wt%. LDPE/IFR/Fe-MMT had a lower heat release rate (HRR), lower total heat release (THR) and more residues than LDPE/IFR/Fe-OMMT at the same loading in the range from 0.5 to 3 wt%. Scanning electron microscopy (SEM) observation showed that both Fe-MMT and Fe-OMMT could promote the formation of continuous and compact intumescent char layer in LDPE/IFR. Both CC and UL-94 tests vitrified that Fe-MMT had better contribution to IFR in fire resistance test. Thermogravimatric (TG) and Mossbauer spectrum etc. revealed that the different efficiency of Fe-OMMT and Fe-MMT should mainly be resulting from the structure difference between Fe-MMT and Fe-OMMT, in which the essential difference might be the different existing state of Fe in two types of MMTs.
Co-reporter:Jun-Bo Zhang, Xiu-Li Wang, Qiu-Xia He, Hai-Bo Zhao, Yu-Zhong Wang
Polymer Degradation and Stability 2014 Volume 108() pp:12-22
Publication Date(Web):October 2014
DOI:10.1016/j.polymdegradstab.2014.06.003
AbstractPoly(1,4-cyclohexylenedimethylene terephthalate) (PCT) is a commercialized semicrystalline high-temperature thermoplastic polyester, but its flammability restricted its applications in some fields. A third monomer, 2-(6-oxido-6H-dibenz < c,e > <1,2> oxaphosphorin-6-yl)-1,4-hydroxyethoxy phenylene (DOPO-HQ-HE), was used to synthesize an intrinsic flame-retardant copolyester through trans-esterification and polycondensation. Its chemical structure was confirmed by 1H NMR and ICP-AES. The crystallization behavior of PCTDs was investigated by DSC and WAXD, and found that the introduction of DOPO-HQ-HE slightly reduced the crystallization ability of PCT. TGA results showed that the incorporation of phosphorus-containing monomer improved the thermal stability of copolyesters both in nitrogen and air. Flynn–Wall–Ozawa method was used to analyze the thermal degradation kinetics of copolyesters, and found that the apparent activation energy was enhanced. The microscale combustion calorimetry (MCC) showed that PCTDs had lower heat release rate and total heat release than PCT. The results of the limiting oxygen index (LOI), the UL-94 vertical and the cone calorimeter test indicated that DOPO-HQ-HE endowed PCTDs with flame-retardant properties to some extent. Besides this, the cone calorimeter results show that the introduction of DOPO-HQ-HE remarkably suppressed the smoke release of PCT. The pyrolysis behaviors of PCT and PCTDs were investigated by Py-GC-MS, and found that the decomposition of PCT chains usually happened at ester bond and followed the random chain scission mechanism. The introduction of DOPO-HQ-HE almost had no effect on the thermal degradation mechanism of PCT.
Co-reporter:Cheng-Liang Deng, Shuang-Lan Du, Jing Zhao, Zhen-Qi Shen, Cong Deng, Yu-Zhong Wang
Polymer Degradation and Stability 2014 Volume 108() pp:97-107
Publication Date(Web):October 2014
DOI:10.1016/j.polymdegradstab.2014.06.008
A traditional intumescent flame retardant (IFR) has very poor water resistance due to the existence of ammonium polyphosphate (APP). How to improve the water resistance of APP or IFR without sacrificing its flame retardancy is an important issue for the wide application of IFR. In this study, the coated APP with polysiloxane shell (Si-APP) was prepared by in situ polymerization, and was used to flame retard polypropylene (PP) together with charring agent (CA). The resulting Si-APP was characterized by Fourier transform infrared spectra (FTIR), transmission electron micrographs (TEM) and thermogravimetric (TG) analysis. The water solubility of Si-APP was also investigated. The thermal stability and combustion behaviors of PP/Si-APP/CA and PP/APP/CA composites were also investigated through TG, limiting oxygen index (LOI), vertical burning test (UL-94), and cone calorimeter (CC) test. The results showed that the coated APP with polysiloxane shell could significantly improve the flame retardancy of IFR PP systems. At a total flame retardant loading of 25 wt%, the LOI value of PP/Si-APP/CA was 34.0%, which was higher than 30.6% of PP/APP/CA, and the UL-94 rating of the former was V-0 in the case of the specimen thickness of 1.6 mm, while the later was V-2 rating. CC test results showed that the average value of heat release rate (HRR), the total heat release (THR), and the peak of smoke production rate (SPR) of PP/Si-APP/CA decreased in comparison with PP/APP/CA system, especially, THR decreased by 50.0%. Further, the char residue of the former increased significantly compared with the latter, greatly increased by 238.9%. In addition, the thermal stability and water resistance of IFR PP composites were also improved due to the modification of APP. The mechanism for the improvement of flame retardancy was also discussed based on the experimental results. All these results illustrate that the coating of APP with polysiloxane shell is an efficient method to improve the flame retardancy and water resistance of APP-containing IFR PP systems.
Co-reporter:Cheng-Liang Deng;Cong Deng;Jing Zhao;Wen-Han Fang;Ling Lin
Polymers for Advanced Technologies 2014 Volume 25( Issue 8) pp:861-871
Publication Date(Web):
DOI:10.1002/pat.3319
In this work, ammonium polyphosphate (APP) was microencapsulated by UV-curable epoxy acrylate (EA) resin. The resulting novel EA-microencapsulated APP (EA-APP) was characterized by Fourier transform infrared spectra, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, granulometry, and thermogravimetric (TG) analysis. EA-APP was used to flame retard polypropylene (PP). The water solubility of EA-APP and the water resistance of PP/EA-APP systems were investigated. The thermal stability and combustion behaviors of PP/EA-APP composites were studied through TG and cone calorimeter (CC) tests, respectively. The water resistance test showed that the EA shell could significantly improve the water resistance of PP/APP. TG data illustrated that the char residue of EA-APP greatly increased by 149% compared with uncoated APP, and the thermal stability of PP/EA-APP composite was improved because of the microencapsulation of APP, with an increment of 248% for the char residue compared with PP/APP. CC test results indicated that the peak value of heat release rate, the total heat release, and the peak of smoke production rate of PP/EA-APP decreased in comparison with PP/APP. The mechanism for the improvement of flame retardancy in CC test was discussed based on the experimental results. EA resin containing a large number of hydroxyl groups might promote the dehydration reaction in EA-APP, which facilitated the formation of char residue and the stabilization of APP. Consequently, the flame-retardant efficiency for APP was improved because of the presence of EA shell. Copyright © 2014 John Wiley & Sons, Ltd.
Co-reporter:Chang-Lei Liu, Gang Wu, Si-Chong Chen, Jiao You, Yu-Zhong Wang
Chinese Chemical Letters 2014 Volume 25(Issue 10) pp:1311-1317
Publication Date(Web):October 2014
DOI:10.1016/j.cclet.2014.07.009
Poly(p-dioxanone)-block-polyethylene glycol diblock copolymers functionalized with pyrene moieties (Py-PPDO-b-PEG) at the chain ends of PPDO blocks were synthesized for preparing anisotropic micelles with improved stability. The micellization and crystallization of the copolymers were investigated by nano differential scanning calorimetry (Nano DSC), transmission electron microscopy (TEM), UV–vis spectrophotometery, fluorophotometer, and dynamic light scattering (DLS), respectively. The results indicated that the aggregation of pyrene induced by intermolecular interaction lead to micellization of Py-PPDO-b-PEG at much lower concentrations than those of PPDO-b-PEG copolymers without pyrene moieties. The aggregation of pyrene moieties may also serve as nucleation agent and therefore enhance the crystallization rate of PPDO blocks. Fluorescence measurements by using Nile Red as the fluorescent agent indicated that the micelles of Py-PPDO-b-PEG have high stability and load capacity for hydrophobic molecules.Crystallization induced micellization of poly(p-dioxanone)-block-polyethylene glycol diblock copolymer functionalized with pyrene moiety were studied. The aggregation of pyrene moieties promotes both micellization of the copolymer and crystallization of the PPDO blocks by serving as heterogeneous nucleation agent, resulted in much higher micelle stability than copolymer without pyrene moieties.
Co-reporter:Lei-Xiao Yu, Yang Liu, Si-Chong Chen, Yue Guan, Yu-Zhong Wang
Chinese Chemical Letters 2014 Volume 25(Issue 3) pp:389-396
Publication Date(Web):March 2014
DOI:10.1016/j.cclet.2013.12.014
Well-defined, reversibly light-responsive amphiphilic diblock copolymer grafted with spiropyran, was prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization. The copolymer self-assembles into polymeric micelles in water and exhibits reversible dissolution and re-aggregation characteristics upon ultraviolet (UV) and visible (Vis)-light irradiation. The fluorescence response of spiropyran immobilized onto the copolymer was light switchable. When nitrobenzoxadiazolyl derivative (NBD) dyes are encapsulated into the core of the micelles, a reversible, light-responsive, dual-color fluorescence resonance energy transfer (FRET) system is constructed and processed, which is well regulated by alternatively UV/vis irradiation. We anticipate these photoswitchable and FRET lighting up nanoparticles will be useful in drug delivery and cell imaging or tracking synchronously.Well-defined amphiphilic diblock copolymer decorated with spiropyran exhibits good reversible photoswitchable and FRET light-responsive properties, which would have a potential application in drug delivery and cell imaging and tracking synchronously.
Co-reporter:Jing Zhao;Cheng-Liang Deng;Shuang-Lan Du;Li Chen;Cong Deng
Journal of Applied Polymer Science 2014 Volume 131( Issue 7) pp:
Publication Date(Web):
DOI:10.1002/app.40065
Abstract
Synergistic flame-retardant effect of halloysite nanotubes (HNTs) on an intumescent flame retardant (IFR) in low-density polyethylene (LDPE) was investigated by limited oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis (TGA), cone calorimeter (CC) test, and scanning electronic microscopy (SEM). The results of LOI and UL-94 tests indicated that the addition of HNTs could dramatically increase the LOI value of LDPE/IFR in the case that the mass ratio of HNTs to IFR was 2/28 at 30 wt % of total flame retardant. Moreover, in this case the prepared samples could pass the V-0 rating in UL-94 tests. CC tests results showed that, for LDPE/IFR, both the heat release rate and the total heat release significantly decreased because of the incorporation of 2 wt % of HNTs. SEM observations directly approved that HNTs could promote the formation of more continuous and compact intumescent char layer in LDPE/IFR. TGA results demonstrated that the residue of LDPE/IFR containing 2 wt % of HNTs was obviously more than that of LDPE/IFR at the same total flame retardant of 30 wt % at 700°C under an air atmosphere, and its maximum decomposing rate was also lower than that of LDPE/IFR, suggesting that HNTs facilitated the charring of LDPE/IFR and its thermal stability at high temperature in this case. Both TGA and SEM results interpreted the mechanism on the synergistic effect of HNTs on IFR in LDPE, which is that the migration of HNTs to the surface during the combustion process led to the formation of a more compact barrier, resulting in the promotion of flame retardancy of LDPE/IFR. In addition, the mechanical properties of LDPE/IFR/HNTs systems were studied, the results showed that the addition of 0.5–2 wt % of HNTs could increase the tensile strength and the elongation at break of LDPE/IFR simultaneously. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40065.
Co-reporter:Hong-Bing Chen, Erin Hollinger, Yu-Zhong Wang, David A. Schiraldi
Polymer 2014 Volume 55(Issue 1) pp:380-384
Publication Date(Web):14 January 2014
DOI:10.1016/j.polymer.2013.07.078
A facile preparation of poly(vinyl alcohol) (PVOH) hydrogels and their derivative PVOH/montmorillonite clay aerogels is reported, using water as solvent and divinylsulfone as crosslinking agent, making use of an environmentally friendly freeze drying process. The materials exhibit significantly increased mechanical properties after crosslinking. The compressive modulus of an aerogel prepared from an aqueous suspension containing 2 wt% PVOH/8 wt% clay increased 29-fold upon crosslinking, for example. Crosslinking of the polymer/clay aerogels decreased the onset decomposition temperature as measured by thermogravimetric analysis, and generated a more continuous structure at higher clay contents. Such polymer/clay aerogels are promising materials for low flammability applications.
Co-reporter:Hai-Bo Zhao, Bo-Wen Liu, Xiao-Lin Wang, Li Chen, Xiu-Li Wang, Yu-Zhong Wang
Polymer 2014 Volume 55(Issue 10) pp:2394-2403
Publication Date(Web):13 May 2014
DOI:10.1016/j.polymer.2014.03.044
Flame-retardant-free and thermo-cross-linkable copolyesters have been synthesized, and their flame retardation and anti-dripping behavior as a consequence of cross-linking during combustion were investigated in detail. TG-DSC simultaneous thermal analysis, rheological analysis, and TGA established the extent and rate of the cross-linking reaction. The extent of cross-linking depends on the content of cross-linkable monomer, PEPE, and the higher the extent of the cross-linking, the better the flame retardance and anti-dripping performance of copolyesters. The large melt viscosity caused by cross-linked networks at high temperature played the most important role in anti-dripping of copolyesters. TG-FTIR results confirmed that the flame-retardant activity of copolyesters mainly took effect in the condensed phase, and XPS results indicated that the carbonization process was aromatization-dominant. SEM and Raman analysis suggested that the char layers were constituted mainly of polyaromatic species with small and uniform microstructures at the surface. Consequently, both the large melt viscosity and the formation of an especially compact char with fine microstructure resulting from cross-linking were considered as the key to the flame retardance and anti-dripping performance of the polymer when subjected to the flame.
Co-reporter:Shou-song Xiao;Ming-jun Chen;Liang-ping Dong
Chinese Journal of Polymer Science 2014 Volume 32( Issue 1) pp:98-107
Publication Date(Web):2014 January
DOI:10.1007/s10118-014-1378-0
Aluminum hypophosphite (AP) was used to prepare flame-retarded thermoplastic polyurethane (FR-TPU) composites, and their flame retardancy, thermal degradation and mechanical properties were investigated by limiting oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis (TGA), cone calorimeter (CC) test, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and tensile test. TPU containing 30 wt% of AP could reach a V-0 rating in the UL-94 test, and its LOI value was 30.2. TGA tests revealed that AP enhanced the formation of residual chars at high temperatures, and slightly affected the thermal stability of TPU at high temperatures. The combustion tests indicated that AP affected the burning behavior of TPU. The peak of heat release rate (PHRR), total heat release (THR) and mass loss rate (MLR) greatly reduced due to the incorporation of AP. The tensile test results showed that both the tensile strength and the elongation at break slightly decreased with the addition of AP. The digital photos and SEM micrographs vitrified that AP facilitated the formation of more compact intumescent char layer. Based on these results mentioned above, the flame-retarding mechanism of AP was discussed. Both the self-charring during the decomposing process of AP and its facilitation to the charring of TPU led to the great improvement in the flame retardancy of TPU.
Co-reporter:Guang-Chen Liu, Yi-Song He, Jian-Bing Zeng, Qiu-Tong Li, and Yu-Zhong Wang
Biomacromolecules 2014 Volume 15(Issue 11) pp:
Publication Date(Web):October 7, 2014
DOI:10.1021/bm5012739
A fully biobased and supertough thermoplastic vulcanizate (TPV) consisting of polylactide (PLA) and a biobased vulcanized unsaturated aliphatic polyester elastomer (UPE) was fabricated via peroxide-induced dynamic vulcanization. Interfacial compatibilization between PLA and UPE took place during dynamic vulcanization, which was confirmed by gel measurement and NMR analysis. After vulcanization, the TPV exhibited a quasi cocontinuous morphology with vulcanized UPE compactly dispersed in PLA matrix, which was different from the pristine PLA/UPE blend, exhibiting typically phase-separated morphology with unvulcanized UPE droplets discretely dispersed in matrix. The TPV showed significantly improved tensile and impact toughness with values up to about 99.3 MJ/m3 and 586.6 J/m, respectively, compared to those of 3.2 MJ/m3 and 16.8 J/m for neat PLA, respectively. The toughening mechanisms under tensile and impact tests were investigated and deduced as massive shear yielding of the PLA matrix triggered by internal cavitation of VUPE. The fully biobased supertough PLA vulcanizate could serve as a promising alternative to traditional commodity plastics.
Co-reporter:Xin-Ke Jing, Xiao-Shi Wang, De-Ming Guo, Yao Zhang, Fei-Yu Zhai, Xiu-Li Wang, Li Chen and Yu-Zhong Wang
Journal of Materials Chemistry A 2013 vol. 1(Issue 32) pp:9264-9272
Publication Date(Web):23 May 2013
DOI:10.1039/C3TA11267E
This manuscript reports a new method to solve the conflict between the flame retardance and anti-dripping of poly(ethylene terephthalate) by introducing azobenzene groups into the main-chain. This novel polyester containing azobenzene units in the main chain (PEAT) was synthesized via esterification and copolycondensation of terephthalic acid, ethylene glycol and azobenzene-4,4′-dicarboxylic acid. TG-DSC, rheological and UV-Vis results proved the occurrence of the thermal and chemical crosslinking reaction by adjacent azobenzene groups. In the TG test, the residue and thermooxidative stability were obviously increased by the high-temperature crosslinking of the azobenzene groups. The cone calorimetric analysis and LOI tests further confirmed the self-extinguishing properties and inhibition of melt-dripping. Elemental analysis results indicated that besides partial decomposition of azobenzene groups into N2, most nitrogen was retained in the residue after high-temperature crosslinking. Besides, the char became more compact with an increase of azobenzene-4,4′-dicarboxylic acid. All the results demonstrated that through the high-temperature crosslinking of the azobenzene group, PEAT exhibited a good balance between flame retardance and anti-dripping properties.
Co-reporter:Rong Yang, Li Chen, Rui Jin and Yu-Zhong Wang
Polymer Chemistry 2013 vol. 4(Issue 2) pp:329-336
Publication Date(Web):24 Aug 2012
DOI:10.1039/C2PY20579C
A series of phosphorus-containing main-chain thermotropic liquid crystalline copolyesters named poly(4,4′-biphenylene decanedioate-co-4,4′-(phenylphosphoryl)dibenzoate) (PBPDP) were synthesized by random polycondensation from mesogenic diol 4,4′-biphenol (BP), decanedioic acid (DA) and phosphorus-containing non-coplanar diacid named 4,4′-(phenylphosphoryl)dibenzoic acid (PPDBA). Chemical structures and physical properties of PBPDPs were characterized by Fourier-transform infrared spectroscopy (FTIR), proton and 31P nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and X-ray diffraction (WAXD). Thermal stability of the copolyesters was determined via thermogravimetric analysis (TGA), and the liquid crystalline behaviours were observed using polarizing optical microscopy (POM). Results showed that the introduction of PPDBA into the copolyester could decrease the liquid crystalline temperature (Tlc) and the isotropic temperature (Ti) as a result of both copolymerization and the non-coplanar structure of PPDBA; furthermore, when the molar ratio of PPDBA reached 15%, the copolyester turned into a semi-crystalline polymer and lost its liquid crystallinity. Thermal stability of the copolyester increased with increasing the content of PPDBA, due to the positive contribution of the phosphorus-containing structure.
Co-reporter:Hong-Bing Chen, Jian-Bing Zeng, Xue Dong, Li Chen and Yu-Zhong Wang
CrystEngComm 2013 vol. 15(Issue 14) pp:2688-2698
Publication Date(Web):24 Jan 2013
DOI:10.1039/C3CE26631A
The crystallization behavior of neat PTT and phosphorus-containing PTT copolyester with specific block chain structure (PTTDs, obtained by solid-state polymerization (SSP)) has been investigated by differential scanning calorimetry (DSC), polarized microscopy (POM) and wide-angle X-ray diffraction (WAXD). The overall crystallization kinetics study shows that crystallization is retarded with introduction of a phosphorus-containing segment. This retardation effect is obvious for PTTD10; however, no greater retardation can be observed with further increasing the phosphorus content, which is attributed to the hindering effect of phosphorus-containing segment and specific chain structure, and is in accordance with the crystallization morphology. The crystallization rate of PTTDs is much lower at high crystallization temperature than that of PTT, which can be explained by the diluent effect of the non-crystallizable chain segment. The result of spherulite growth is in accordance with DSC study. The rigid amorphous fraction (RAF) is also calculated, which increases with increasing phosphorus content, suggesting that RAF is not the main factor for retarded crystallization. The main factors of retarded crystallization are probably caused by the diluent effect and the hindering effect of the specific chain structure. With incorporation of phosphorus-containing segments, the transition temperature is slightly changed; however, the equilibrium melting temperature (Tm0) of the copolyester decreases. The phosphorus-containing segment plays the role of nucleation agent at regime III.
Co-reporter:Hong-Bing Chen, Xue Dong, David A. Schiraldi, Li Chen, De-Yi Wang, Yu-Zhong Wang
Journal of Analytical and Applied Pyrolysis 2013 Volume 99() pp:40-48
Publication Date(Web):January 2013
DOI:10.1016/j.jaap.2012.11.003
A novel phosphorus-containing poly(trimethylene terephthalate) (PTT) derived from 2-(6-oxido-6H-dibenz〈c,e〉〈1,2〉oxaphosphorin-6-yl)-1,4-hydroxyethoxy phenylene was synthesized via solid state polymerization, and its chemical structure was confirmed with 1H NMR. The thermal stability of the resulting copolyester was analyzed by thermogravimetric analysis. With the introduction of phosphorus-containing segments, polyester onset weight-loss temperatures in both nitrogen and air are enhanced. Thermal degradation kinetics were analyzed using the Flynn–Wall–Ozawa method, which showed a decreased activation energy for the copolyester compared with that for neat PTT, strongly suggesting that the increased onset weight-loss temperature in nitrogen is a result of enhanced carbonization. Microscale combustion calorimetry was carried out to test the flammability behavior of the copolyester; improved flame-retardant properties were observed with incorporated phosphorus components. Py-GC–MS testing revealed that the pyrolysis of phosphorus-containing copolyester is not significantly affected by the phosphorus incorporation.Highlights► P-containing monomer was incorporated into poly(trimethylene terephthalate) (PTT) via solid state polymerization. ► Onset weight-loss temperatures of the P-containing PTT copolyester in both nitrogen and air were enhanced. ► The activation energy for the copolyester in nitrogen was decreased compared with that for neat PTT. ► Improved flame-retardant properties tested by microscale combustion calorimetry were observed with incorporated phosphorus components. ► Py-GC–MS testing revealed that the pyrolysis of the P-containing copolyester is not significantly affected.
Co-reporter:Yu-Rong Zhang, Xiu-Li Wang, Guo-Ming Zhao, Yu-Zhong Wang
Carbohydrate Polymers 2013 Volume 96(Issue 1) pp:358-364
Publication Date(Web):1 July 2013
DOI:10.1016/j.carbpol.2013.03.093
•TPS with improved flow properties, thermal stability and toughness were achieved.•OS has good compatibility with starch matrix.•Tg and storage modulus of TPS were further lowered as OS was introduced.Thermoplastic starch was prepared by adding oxidized starches and glycerol together into starch. The addition of oxidized starch improved the rheological properties and also increased the toughness of thermoplastic starch. Compared with TPS30, the elongation at break increased from 126.8% to 152.5% when 5 wt% OS 117% was added. Good compatibility of thermoplastic starch between the matrix and oxidized starch was confirmed by SEM. The addition of oxidized starch lowered the storage modulus and glass transition temperature (Tg) of thermoplastic starch, decreasing Tg from 34.1 to 30 °C when 10 wt% OS117% was added. The thermal stability of blending was improved by adding oxidized starches, i.e. when 5 wt% OS70% was added, T5% increased from 134 to 156 °C.
Co-reporter:Hao Wang, Chang-Lei Liu, Gang Wu, Si-Chong Chen, Fei Song and Yu-Zhong Wang
Soft Matter 2013 vol. 9(Issue 36) pp:8712-8722
Publication Date(Web):17 Jul 2013
DOI:10.1039/C3SM51858B
The morphological evolution and phase transition of a branched crystalline-coil multi-block copolymer, poly(p-dioxanone)-block-poly(ethylene glycol) (PPDOstar-b-PEG), in aqueous solution under heating and cooling were investigated. The changes in size and morphology of the nano-aggregates were monitored by dynamic light scattering (DLS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). A semitransparent and uniform dispersion of nano-aggregates with star anise-like morphology was obtained from PPDOstar-b-PEG at room temperature. The dispersion gradually turned transparent during heating to 80 °C because of the melting of the crystallized PPDO blocks. The crystals with low regularity melted first leading to dissociation of the star anise nano-aggregates to flake-like particles. The copolymer formed sphere-like micelles when the temperature was high enough for melting all PPDO crystals. During the cooling run, a hysteresis of phase transition was observed because of the supercooling of crystallization. The morphological evolution of the copolymer micelle suggested that the formation of the star anise-like nano-aggregates was a hierarchical assembly process. A “crystallization induced hierarchical assembly” mechanism was therefore proposed to explain the formation of the star anise-like nano-aggregates. Metastable flake-like nano-particles formed at the initial stage of crystallization of PPDO blocks. The hydrophobic core of the flake was composed of several crystal lamellae or plates piled up in a layer-by-layer fashion. With further crystallization of PPDO blocks, the flakes tended to aggregate because of the variation of the hydrophilic–hydrophobic balance. The active edge of crystalline lamellae in the hydrophobic core of one flake may induce two different growth modes: epitaxial growth with amorphous spherical micelles and interparticle interpenetration crystallization in the amorphous region of other flakes. The branched structure of the nano-particles was therefore formed driven by interparticle interpenetration crystallization and epitaxial crystallization simultaneously.
Co-reporter:Xin-Ke Jing, De-Ming Guo, Jun-Bo Zhang, Fei-Yu Zhai, Xiu-Li Wang, Li Chen, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 12) pp:4539
Publication Date(Web):March 5, 2013
DOI:10.1021/ie302919n
Phosphorus-containing poly(ethylene terephthalate-co-diethylene terephthalate) (PEDT) with a low melting temperature was synthesized through esterification and copolycondensation of terephthalic acid, ethylene glycol, diethylene glycol (DEG), and 3-(hydroxyphenylphosphinyl)propionic acid (HPPPA). DSC results showed that PEDTs still were crystallizable and that the lowest melting temperature of the PEDTs was reduced to 118.0 °C although the chain regularity was destroyed by the incorporation of comonomers. It was found that the addition of HPPPA can improve the thermal oxidative stability of copolyesters. The results of the limiting oxygen index (LOI) test, the UL-94 vertical test, and the cone calorimeter test indicated that HPPPA endowed PEDT with good flame-retardant properties. The LOI values of the PEDTs were increased to 30.5–34.8, the UL-94 ratings of vertical burning were improved to V-0, and both the peak heat release rate (pHRR) and the total heat release (THR) obviously decreased.
Co-reporter:Zhao-Zan Xu, Jian-Qian Huang, Ming-Jun Chen, Yi Tan, Yu-Zhong Wang
Polymer Degradation and Stability 2013 Volume 98(Issue 10) pp:2011-2020
Publication Date(Web):October 2013
DOI:10.1016/j.polymdegradstab.2013.07.010
An efficient flame retardant polymeric synergist poly[N4-bis(ethylenediamino)-phenyl phosphonic-N2, N6-bis(ethylenediamino)-1,3,5-triazine-N-phenyl phosphonate] (PTPA) was designed and synthesized from cyanuric chloride, ethylenediamine and phenylphosphonic dichloride. It was characterized by Fourier Transform Infrared (FTIR), 1H NMR and 31P NMR, Elemental Analysis (EA) and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Combined with ammonium polyphosphate (APP), a new intumescent flame retardant (IFR) was obtained. The flammability behaviors of polypropylene (PP)/IFR system were investigated by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimetry. With 25 wt% of IFR (APP:PTPA = 2:1), the PP/IFR system could achieve a LOI value of 34.0% and UL-94 V-0 rating, and the heat release rate (HRR), peak heat release rate (PHRR), total heat release (THR) and smoke production rate (SPR) were considerably reduced, especially HRR and SPR were decreased by 85% and 79%, respectively. The results indicate that there is an excellent synergism between APP and PTPA, which endows PP with both good flame retardancy and good smoke suppression. Furthermore, the thermal degradation mechanism of IFR and the flame-retardant mechanism of PP/IFR system were investigated by thermogravimetric analysis (TGA), FT-IR, TG-FTIR and scanning electron microscope (SEM). The study on the flame-retardant mechanism of IFR indicated that a structure containing –CN was formed due to the reaction between APP and PTPA.
Co-reporter:Bin Zhao, Li Chen, Jia-Wei Long, Rong-Kun Jian, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 48) pp:17162
Publication Date(Web):November 5, 2013
DOI:10.1021/ie4009056
A novel binary flame-retardant system was formed by introducing aluminum hypophosphite (AP) and aluminum isobutylphosphinate (APBu) together for PA6. The optimum flame retardant formulation was 1:1 (AP:APBu, 15 wt % in total), and the resulting flame-retardant PA6 could achieve a LOI value of 28.3 vol % and UL-94 V-0 rating. Cone calorimeter testing showed the samples containing binary flame retardants became less flammable with lower peak heat release rate (PHRR, 259 kW/m2). Dynamic oscillatory rheology and simultaneous thermogravimetry–differential scanning calorimetry results proved that cross-linking reactions existed in the samples containing AP. Morphology of the char layers was analyzed via SEM and laser Raman spectroscopy, and the results demonstrated the samples containing both AP and APBu formed more effective char. These results revealed that flame-retardant synergism existed between AP and APBu when they were combined to flame retard PA6. Consequently, a brief synergistic mechanism in this system was proposed.
Co-reporter:Zhen-Qi Shen, Li Chen, Ling Lin, Cheng-Liang Deng, Jing Zhao, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 25) pp:8454
Publication Date(Web):June 5, 2013
DOI:10.1021/ie4010546
In this work, flame-retardant ethylene–propylene–diene terpolymer (EPDM) composites were prepared by incorporating intumescent flame-retardant (IFR) together with two different organically modified layered nanoparticles: montmorillonite (OMMT) and layered double hydroxides (OLDH). The morphology, fire behavior, thermal stability, flame-retardant synergism, and mechanical properties of the flame-retardant EPDM nanocomposites were studied. The introduction of a certain amount of OMMT (or OLDH) in the intumescent flame-retardant EPDM led to the considerable enhancement of flame retardance, thermal stability, and mechanical properties. Especially, the EPDM-IFR30-OLDH2 composite (100 phr EPDM, 30 phr IFR, and 2 phr OLDH) presented the highest tensile strength and could pass a UL-94 test V-0 rating; while the EPDM-IFR30-OMMT2 composite (100 phr EPDM, 30 phr IFR, and 2 phr OMMT) showed the lowest peak heat release rate (pHRR) and total heat release (THR) values. Different flame-retardant performances should be attributed to their own characteristics, dispersion state in EPDM matrix, and the change of structure during burning. The flame-retardant mechanisms for the composites were proposed to be condensed phase activity.
Co-reporter:Liang-Jie Li, Rong-Tao Duan, Jun-Bo Zhang, Xiu-Li Wang, Li Chen, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 15) pp:5326
Publication Date(Web):March 22, 2013
DOI:10.1021/ie400224z
A series of phosphorus-containing copolyester prepolymers were first sythesized from dimethyl terephthalate (DMT), ethylene glycol (EG), and 2-carboxyethyl (phenyl)phosphinic acid (CEPPA) by molten transesterification and polycondensation, and then solid-state polymerization (SSP) was conducted for different reaction times (tSSP) so as to prepare higher molecular weight copolymers. The intrinsic viscosity was increased with the increase of tssp, but decreased with the increase of CEPPA content. The sequence distribution of resultant copolyesters was analyzed by 1H NMR. It was found that the randomness of copolyesters was decreased after SSP, and the transesterification occurred mainly at the ester bonds formed by CEPPA and EG, resulting in the chain growth. DSC results showed that SSP treatment was favorable to enhance the crystallization ability of the obtained copolyesters.
Co-reporter:Bin Zhao, Li Chen, Jia-Wei Long, Hong-Bing Chen, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 8) pp:2875
Publication Date(Web):February 5, 2013
DOI:10.1021/ie303446s
Aluminum hypophosphite (AP) and aluminum isobutylphosphinate (APBu) were used to flame retard polyamide 6 (PA6). Addition of either AP or APBu resulted in an increased LOI value, UL-94 V-0 rating, and decreased heat release in cone calorimetric tests. However, different chemical structures of two flame retardants caused different flame-retardant effects: APBu endowed PA6 a higher LOI value and better UL-94 result than did AP. Decomposition pathways of AP, APBu, and the corresponding composites were investigated using TGA, TG-IR, Py-GC/MS, and FTIR characterization of the residues. The introduction of AP changed the thermal stability and decomposition behavior of the composites due to the cross-linking reactions occurred, which were proved by rheological analysis and TG-DSC. APBu could not essentially affect the composition of pyrolysis products and decomposition behaviors, but mainly produced phosphorus-containing free radical scavengers in the gaseous phase, which were positive to flame retardation. Finally, the proposed flame-retardant mechanisms of such systems were summarized.
Co-reporter:Xue-Qi Liu, De-Yi Wang, Xiu-Li Wang, Li Chen, Yu-Zhong Wang
Polymer Degradation and Stability 2013 Volume 98(Issue 9) pp:1731-1737
Publication Date(Web):September 2013
DOI:10.1016/j.polymdegradstab.2013.06.001
A novel functionalized α-zirconium phosphate (F-ZrP) modified with intumescent flame retardant was synthesized by co-precipitation method and characterized. Poly (lactic acid) (PLA)/F-ZrP nanocomposites were prepared by melt blending method. The thermal stability and combustion behavior of PLA/F-ZrP nanocomposites were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94), scanning electronic microscopy (SEM), and cone calorimeter test (CCT). The results showed that the addition of flame retardant F-ZrP slightly affect PLA's thermal stability, but significantly improve the flame retardancy of PLA composites. In comparison with neat PLA, the LOI value of PLA/F-ZrP was increased from 19.0 to 26.5, and the UL-94 rating was enhanced to V-0 as the loading of F-ZrP at 10%. SEM results suggested the introduction of F-ZrP in the PLA system can form compact intumescent char layer during burning. All these results showed that the F-ZrP performed good flame retardancy for PLA.
Co-reporter:Qiang Lv, Jian-Qian Huang, Ming-Jun Chen, Jing Zhao, Yi Tan, Li Chen, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 27) pp:9397-9404
Publication Date(Web):June 5, 2013
DOI:10.1021/ie400911r
An effective flame retardant and smoke suppression oligomer, poly(melamine-ethoxyphosphinyl-diisocyanate) (PMPC), was successfully synthesized. The chemical structure was characterized by Fourier transform infrared (FTIR), 1H nuclear magnetic resonance (1H NMR), and 31P nuclear magnetic resonance (31P NMR) spectroscopies. PMPC was used alone as the flame retardant for epoxy resins (EP). The results showed that PMPC endowed EP with good flame retardancy. The limiting oxygen index (LOI) value of a EP/PMPC system containing 20 wt % PMPC increased to 28.0%, and can achieve a UL-94 V-0 rating. The cone calorimeter data showed that the heat release rate (HRR) and total heat release (THR) were considerably reduced with the addition of PMPC, and the smoke production rate (SPR), total smoke production (TSP), and carbon monoxide production (COP) were also reduced. Moreover, the thermal degradation behavior of PMPC and the flame-retardant mode of the EP systems were also investigated.
Co-reporter:Juan Li, Ping-Lai Xu, Ying-Ke Zhu, Jiang-Ping Ding, Li-Xin Xue and Yu-Zhong Wang
Green Chemistry 2012 vol. 14(Issue 12) pp:3260-3263
Publication Date(Web):20 Sep 2012
DOI:10.1039/C2GC36294E
An efficient solution has been built for the chemical recycling of carbon fiber/epoxy composites by oxidative degradation under mild conditions with acetone and H2O2. Clean CF can be obtained after reacting at 60 °C for 30 min. The decomposition ratio of epoxy is above 90%, and the strength of CF remains more than 95% of its original strength.
Co-reporter:Hai-Bo Zhao, Li Chen, Jun-Chi Yang, Xin-Guo Ge and Yu-Zhong Wang
Journal of Materials Chemistry A 2012 vol. 22(Issue 37) pp:19849-19857
Publication Date(Web):08 Aug 2012
DOI:10.1039/C2JM34376B
In this manuscript, contradiction between the non-flammability and non-dripping of polyesters could be solved by copolymerizing terephthalic acid and ethylene glycol together with a pendent phenylethynyl-based monomer named 4-(phenylethynyl) di(ethylene glycol) phthalate (PEPE), which exhibited a cross-linkable nature at a proper temperature. TG-DSC simultaneous thermal analysis, FTIR, dissolution tests and rheological investigations proved the thermal cross-linking behavior of the copolyester, which was not active at the temperature of polymerization and processing but could cross-link rapidly at higher temperature before burning. LOI tests, cone calorimetry and small-scale flame tests further confirmed the self-extinguishment and inhibition for melt-dripping could be achieved through the cross-linking during burning, despite the absence of any flame-retardant element (say, bromine, chlorine, phosphorus, or nitrogen, etc.). Rheological analyses and the SEM microphotographs of the char showed P(ET-co-P)s exhibited a greater complex viscosity through the cross-linking at high temperature, leading to compact char residue, flame-retardant and anti-dripping effects.
Co-reporter:Ling-Xi Zeng, Ming-Jing Liu, Si-Chong Chen, Jian-Bing Zeng and Yu-Zhong Wang
Polymer Chemistry 2012 vol. 3(Issue 9) pp:2537-2544
Publication Date(Web):22 Jun 2012
DOI:10.1039/C2PY20331F
The crystallization behaviour and morphology of a polymer blend based on branched poly(p-dioxanone)–poly(lactic acid) block copolymer (PLA-b-LCB-PPDO) and linear PPDO with immiscible PPDO and PLA blocks has been investigated. Although the PPDO and PLA blocks are immiscible with each other, an interesting interpenetrating spherulite morphology, which always occurs in miscible blends, was observed. Since the chemical bonding and branching molecular structure of the copolymer may resulted in a relatively small phase separation, the crystals of PPDO can nucleate and grew confined inside the matrix of pre-crystallized PLA spherulites. The morphologies of both PLA and PPDO crystals were significantly affected by the crystallization condition and process. Both the growth rate and nucleation rate of PPDO segments were enhanced rather than depressed under the confinement crystallization imposed by pre-crystallized PLA when relatively small amounts of PLA were added. The nucleation density of PPDO increased obviously with a small change in the self-nucleation temperature of PLA suggesting that the pre-crystallized PLA may serve as a heterogeneous nucleation agent for the crystallization of PPDO segments.
Co-reporter:Wen-Da Li, Jian-Bing Zeng, Xiao-Jie Lou, Jing-Jing Zhang and Yu-Zhong Wang
Polymer Chemistry 2012 vol. 3(Issue 5) pp:1344-1353
Publication Date(Web):26 Mar 2012
DOI:10.1039/C2PY20068F
A series of poly(butylene terephthalate)-poly(butylene succinate) (PBT-PBS) copolyesters were synthesized by the melt chain-extension reaction of dihydroxyl terminated PBT (HO-PBT-OH) and PBS (HO-PBS-OH) prepolymers using toluene-2,4-diisoyanate (TDI) as a chain extender. Transesterification between PBT and PBS during the chain-extension reaction has been investigated in detail. Both random and block PBT-PBS copolymers can be synthesized by changing the prepolymers' molecular weights at a given reaction time and temperature. The chemical structures and sequence distributions of the copolyesters were analyzed by proton nuclear magnetic resonance (1H-NMR) spectroscopy. The thermal transition behaviours of copolyesters with different sequence distribution were characterized by differential scanning calorimeter (DSC). The number-average molecular weight (Mn) of HO-PBT-OH played a dominant role in the sequence distribution of the resulting copolyesters. The degree of randomness of the copolymer was around 1 when Mn of HO-PBT-OH was 5000 g mol−1 regardless of that of HO-PBS-OH, it decreased to less than 1 when Mn of HO-PBT-OH was more than 10000 g mol−1, and it gradually decreased with the increase in Mn of HO-PBS-OH. The copolyesters with different degrees of randomness showed different thermal transition and crystallization behaviours.
Co-reporter:Si-Chong Chen, Ling-Ling Li, Hao Wang, Gang Wu and Yu-Zhong Wang
Polymer Chemistry 2012 vol. 3(Issue 5) pp:1231-1238
Publication Date(Web):14 Mar 2012
DOI:10.1039/C2PY20016C
A novel multi-branched crystalline-coil block copolymer composed of hydrophilic polyethylene glycol (PEG) block and multi-branched crystallisable poly(p-dioxanone) (PPDO) block was prepared. Firstly, multi-branched PPDO was prepared via polycondensation of AB2-type HOOC-PPDO-2OH precursor, which was synthesized by using 2,2-bis(hydroxymethyl)propionic acid as initiator for ring opening polymerization of p-dioxanone; then the multi-branched PPDO-b-PEG copolymer was obtained by coupling the end hydroxyl group of multi-branched PPDO with carboxylated mPEG using dicyclohexylcarbodiimide as dehydrator. The molecular structures of polymers formed in each step were characterized by NMR and GPC. The results confirmed the successful preparation of the target product, and the molecular characteristics of the multi-branched PPDO, such as chain length of the blocks and branch density, could be facilely controlled. In addition, the micelle of the copolymer in aqueous solution was investigated by fluorescent probe, TEM, DLS, DSC and NMR. The results indicated that the copolymer in aqueous solution can form “star anise”-like micelles and the micellization behavior was determined by the composition and molecular architecture of the copolymer.
Co-reporter:Jian-Bing Zeng, Qun-Ying Zhu, Xi Lu, Yi-Song He and Yu-Zhong Wang
Polymer Chemistry 2012 vol. 3(Issue 2) pp:399-408
Publication Date(Web):01 Dec 2011
DOI:10.1039/C1PY00456E
A series of biodegradable double crystalline poly(ethylene succinate)-b-poly(butylene succinate) (PES-b-PBS) multiblock copolymers with various PES and PBS block lengths were successfully synthesized by chain-extension reaction of dihydroxylated poly(ethylene succinate) (HO-PES-OH) and poly(butylene succinate) (HO-PBS-OH) using 1,6-hexamethylene diisocyanate (HDI) as a chain-extender. The compositions and structures were characterized by proton nuclear magnetic resonance spectroscopy (1H NMR). The miscibility of amorphous phase and crystallization behaviors of the two blocks were investigated by standard differential scanning calorimetry (DSC), temperature modulated DSC (TMDSC), polarized light optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). When the block length of PBS and PES were less than 4710 g mol−1, the amorphous phases of the two blocks were miscible. As the block length increased to more than 5430 g mol−1, the amorphous phases of the two blocks changed to be partially miscible, and the miscibility decreased with further increasing the block lengths. The crystallizability of both PBS and PES blocks increased with an increase in size of their blocks. POM observation showed that the copolymers displayed banded spherulitic morphologies, and the crystallization of PES happened in confined space after crystallization of PBS blocks. WAXD analysis suggested that the crystals of the copolymers were composed of crystals of both PES and PBS blocks.
Co-reporter:Yu-Rong Zhang, Xiu-Li Wang, Guo-Ming Zhao, Yu-Zhong Wang
Carbohydrate Polymers 2012 Volume 87(Issue 4) pp:2554-2562
Publication Date(Web):1 March 2012
DOI:10.1016/j.carbpol.2011.11.036
A highly efficient method for preparing oxidized starches with a high degree of oxidation (DO) was developed, using CuSO4 and H2O2 respectively as a catalyst and an oxidant. The effect of different parameters including starch origin, oxidant content, temperature, catalyst content, and reaction time on the DO was investigated systematically. In the present study, only 0.5% of catalyst was added, and the reaction time could be reduced to 1 h, while in the previous study the reaction time of 72 h was necessary to achieve almost the same DO without a catalyst. The structures and properties of oxidized starches were characterized by FT-IR, DSC, TGA, XRD, and transmittance light testing. The oxidation reduced the intrinsic viscosity and thermal stability of the oxidized starches, and could change the crystalline structures into amorphous states when the DO reached 56.3%. When temperature and/or DO increased, the transmittance of suspended solution of oxidized starch increased correspondingly.Highlights► Oxidized starches with high DO value were prepared using CuSO4 and H2O2 respectively as a catalyst and oxidant. ► The oxidization time was reduced to 1 h when 0.5% CuSO4 was added. ► The oxidation reduced the intrinsic viscosity, thermal stability, and crystallinity of starch. ► The transmittance of oxidized starch solution was increased when temperature and/or DO was enhanced.
Co-reporter:Juan Li, Chenhao Ke, Liang Xu, Yuzhong Wang
Polymer Degradation and Stability 2012 Volume 97(Issue 7) pp:1107-1113
Publication Date(Web):July 2012
DOI:10.1016/j.polymdegradstab.2012.04.005
A hyperbranched polyamine charring agent (HPCA) containing triazine was prepared by using 4,4′-oxybisbenzenamine and cyanuric trichloride through A2 + B3 approach. The structure and thermal stability of the product were characterized by Fourier transform infrared spectrometry (FT–IR), nuclear magnetic resonance spectrometry (1H NMR) and thermogravimetric analysis (TGA). It is shown that the carbonaceous residue at 700 °C is higher than 60 wt% suggesting a good char forming ability. Intumescent flame retarded acrylonitrile-butadiene-styrene (IFR-ABS) was prepared with HPCA and ammonium polyphosphate (APP) via melt blending. The flame retardance and thermal properties of the IFR-ABS were studied through limited oxygen index (LOI) and UL-94 vertical burning. The thermal degradation and char forming behaviour was tested with TGA and the morphology of char layer was observed by using scanning electron microscopy (SEM). The results show that a good synergistic effect is present between HPCA and APP. The calculated carbonaceous residue at 800 °C is 24.3 wt%, however the experimental value is 49.7 wt%, which is twice the former. Furthermore, the HPCA and APP have a promoting effect for char forming of IFR-ABS during combustion, for example, there is little carbonaceous residue for ABS at 550 °C according to TGA results in air, but there is 18.4 wt% carbonaceous residue for IFR-ABS with 25 wt% flame retardants. Moreover, the LOI for IFR-ABS is improved to 26.9 from 18.0 for ABS, and UL-94 V-0 rating is achieved with 30 wt% flame retardants.
Co-reporter:Wei Liu, Li Chen, Yu-Zhong Wang
Polymer Degradation and Stability 2012 Volume 97(Issue 12) pp:2487-2491
Publication Date(Web):December 2012
DOI:10.1016/j.polymdegradstab.2012.07.016
A novel flame retardant, poly (1,2-dicarboxyl ethylene spirocyclic pentaerythritol bisphosphonate) (PEPBP) has been synthesized by the reaction of spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride (SPDPC) with tartaric acid (TA). PEPBP was used as the flame-retardant finishing agent for cotton fabrics. The flame retardancy of the samples was characterized by limiting oxygen index (LOI) and the vertical burning test. The cotton fabric sample with 21.2 wt% of PEPBP has a LOI value of 33.8, which is 14.4 higher than that of the untreated cotton sample. The treated cotton fabrics have shorter after-glow time, shorter char length and no after-flame during the vertical burning test. The thermal decomposition behaviors of the fabrics, the chemical structures and morphologies of the residues of the fabrics were investigated using thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM), respectively, and a possible flame retardant mechanism was discussed.
Co-reporter:Ming-Jun Chen, Zhu-Bao Shao, Xiu-Li Wang, Li Chen, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 29) pp:9769
Publication Date(Web):July 6, 2012
DOI:10.1021/ie301004d
A novel nitrogen–phosphorus flame retardant, 2-carboxyethyl(phenyl)phosphinic acid melamine salt (CMA), was synthesized by the reaction of 2-carboxyethyl(phenyl)phosphinic acid with melamine in aqueous solution, and it was characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), inductively coupled plasma-atomic emission spectrometry (ICP-AES), elemental analysis, and thermogravimetric analysis (TGA). Halogen-free flame-retardant flexible polyurethane foams (FPUF) were prepared successfully by using CMA as a flame retardant. The effects of CMA content on the mechanical, thermal, and flame-retardant properties of FPUF were investigated by tensile test, TGA, limiting oxygen index (LOI), flame propagation test (Cal T.B. 117A-Part I standard), and cone calorimeter. The foam morphology of FPUF was studied via scanning electron microscopy (SEM). The results showed that CMA endowed FPUF with good flame-retardant properties. FPUF containing only 12 wt % CMA can pass Cal T.B. 117A-Part I standard, and its LOI value was increased from 18.2 (for FPUF without CMA) to 24.1. Particularly, the addition of CMA almost did not decrease the mechanical properties of the resulting flame-retardant FPUFs.
Co-reporter:Hong-Bing Chen, Qian Zhou, Xue Dong, Yi Zhang, Li Chen, Yu-Zhong Wang
Polymer Degradation and Stability 2012 Volume 97(Issue 6) pp:905-913
Publication Date(Web):June 2012
DOI:10.1016/j.polymdegradstab.2012.03.030
This paper deals with the thermal decomposition behavior of PTT and its two different phosphorus-containing copolyesters, one containing 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phospha-phenanthrene-10-oxide (DDP) with phosphorus in the pendent group, the other containing bis-4-carboxyphenyl phenyl phosphine oxide (BCPPO) with phosphorus in the backbone. TGA-FTIR and Pyrolysis-GC/MS were used to investigate the corresponding volatile products under nitrogen atmosphere. Both PTT and its phosphorus-containing copolyesters showed one decomposition stage between 330 and 446 °C. The introduction of phosphorus decreased the onset decomposition temperature due to the comparative weak P–C bond. No obvious absorption peak of P–C bond is detected with FTIR in volatile products for its low content and weak absorption. The analysis of volatile products of TGA and Pyrolysis-GC/MS revealed that they underwent different way of thermal decomposition for the different decomposition conditions. Possible thermal decomposition schemes are proposed and mass spectra of some decomposition products are also listed.
Co-reporter:Yan-Bing Luo, Xiu-Li Wang, Yu-Zhong Wang
Polymer Degradation and Stability 2012 Volume 97(Issue 5) pp:721-728
Publication Date(Web):May 2012
DOI:10.1016/j.polymdegradstab.2012.02.011
The longer-than-one-year hydrolytic degradation of poly (lactic acid) (PLA)/TiO2 nanocomposites was investigated in phosphate buffer solution of pH 7.4 at 37 °C so as to elucidate the effect of nanofillers on the degradation characteristics of PLA. The temporal changes in appearance, water absorption, number-average molecular weight (Mn), glass transition temperature, melting temperature, and crystallinity of the samples were traced. The results showed that the heterogeneous degradation and bulk-erosion were general mechanisms for PLA and its TiO2 nanocomposites. The change in surface morphology and molecular weight after hydrolysis revealed that the hydrolysis of nanocomposites occurred at the interface of PLA matrix and nanofillers, and the degradation rate was accelerated by the addition of the TiO2 nanofillers. The dispersion of nanofillers in polymer matrix affected the water absorption and degradation rate. The rapid increase of crystallinity also affected the degradation rate of nanocomposites. The present study suggested that the hydrolyzability of PLA could be controlled by adding TiO2 nanoparticles.
Co-reporter:Li Chen, Yuan Luo, Zhi Hu, Gong-Peng Lin, Bin Zhao, Yu-Zhong Wang
Polymer Degradation and Stability 2012 Volume 97(Issue 2) pp:158-165
Publication Date(Web):February 2012
DOI:10.1016/j.polymdegradstab.2011.11.003
Compared with poly(butylene terephthalate) (PBT), glass-fibre-reinforced poly(butylene terephthalate) (GF-PBT) is difficult to flame retard with halogen-free flame retardants. In the present study, the aluminium salt of hypophosphorous acid (AP) was used as a flame retardant for GF-PBT. A series of flame-retardant GF-PBT composites was prepared via melt compounding. The flame retardance and combustion behaviour of the composites were studied by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimetric test. Thermal behaviours and thermal decomposition kinetics were investigated by thermogravimetric analysis (TGA) under N2 atmosphere. The addition of AP to the composites could result in an increased LOI value, a UL-94 V-0 (1.6 mm) classification and a better fire performance in cone calorimetric tests. The char morphology observation after flame-retardant tests, calculation of decomposition kinetics, X-ray photoelectron spectroscopy (XPS) and infra-red spectral analysis of the char residue confirmed the condensed-phase flame-retardant mechanism. Furthermore, the mechanical properties of the flame-retardant composites were not deteriorated, retaining an acceptable level.
Co-reporter:Yuan-Wei Yan, Li Chen, Rong-Kun Jian, Shuang Kong, Yu-Zhong Wang
Polymer Degradation and Stability 2012 Volume 97(Issue 8) pp:1423-1431
Publication Date(Web):August 2012
DOI:10.1016/j.polymdegradstab.2012.05.013
An intumescent flame-retardant (IFR) system, which was comprised of a novel carbonization agent (CA) and ammonium polyphosphate (APP), was prepared for general purpose polystyrene. Thermal degradation and flame retardance of the PS/IFR composites were studied. The results of LOI and UL-94 test showed that when the content of APP and CA was 22.5 and 7.5 wt%, respectively, the LOI value of PS/IFR composite was 32.5%, and a V-0 classification could be achieved. The TGA data indicated that there was a synergistic effect between CA and APP. The cone calorimeter data showed that the heat release rate (HRR), the total heat release (THR) and the mass loss rate (MLR) were reduced largely with the addition of IFR. Some cone calorimeter data, such as smoke production rate (SPR), total smoke production (TSP) and carbon monoxide production (COP), revealed that the IFR could greatly suppress the generation of the smoke during the material flaming. The study on the flame-retardant mechanism of IFR indicated that a steady structure containing P–O–C was formed due to the reaction between APP and CA. The mechanical properties of PS and PS/APP/CA3:1 were also investigated, and the results showed that, compared to those of the neat PS, the tensile strength and the flexural strength of the PS/IFR composite decreased to a certain extent.
Co-reporter:Hong-Bing Chen;Yi Zhang;Li Chen;Wei Wang;Bin Zhao
Polymers for Advanced Technologies 2012 Volume 23( Issue 9) pp:1276-1282
Publication Date(Web):
DOI:10.1002/pat.2042
In order to improve the flame retardancy of the semi-biobased polyester, poly(trimethylene terephthalate) (PTT), bis-4-carboxyphenyl phenyl phosphine oxide (BCPPO) was used as a third monomer to synthesize a novel main-chain phosphorus-containing copolyester, poly(trimethylene terephthalate-co-BCPPO)s (PTTBP), through melt polycondensation. Phosphorus analysis of the resulting polymers suggests that BCPPO has been introduced to PTT chain successfully. 1H and 31P nuclear magnetic resonance spectra further confirm the random chemical structure. The thermal behavior was investigated by differential scanning calorimetry and thermogravimetric analysis. The introduction of BCPPO to PTT lowered the melting point and crystallization ability because of the random copolymerization and the rigid structure of BCPPO, and the thermal stabilities of PTTBP were improved in air but decreased in nitrogen. Rheological investigations showed that the complex viscosities of all the samples were independent of frequency at low frequency (say lower than 100 rads), and shear thinning effect occurred at higher frequency. The cone calorimeter was used to test the fire behavior of PTTBP, and the results suggested that the novel copolyester had good flame retardance. Copyright © 2011 John Wiley & Sons, Ltd.
Co-reporter:Yi-Song He, Jian-Bing Zeng, Shao-Long Li, Yu-Zhong Wang
Thermochimica Acta 2012 Volume 529() pp:80-86
Publication Date(Web):10 February 2012
DOI:10.1016/j.tca.2011.11.031
Biodegradable blend of poly(butylene succinate) (PBS) and poly(ethylene succinate) (PES) was prepared by solution blending and casting method with chloroform as a mutual solvent. Miscibility of the blends was investigated by differential scanning calorimetry (DSC). The results indicated that PBS and PES were partially miscible. Crystallization kinetics, crystalline morphology and crystal structure of the blends were studied by DSC, polarized optical microscope (POM), and wide-angle X-ray diffraction (WAXD), respectively. Nonisothermal and isothermal crystallization kinetics suggested that the crystallizability of PBS in the blends decreased first and then increased with increase in PES content, and that of PES increased steadily with increase in PBS content. POM observation illustrated that the rich component formed a continuous phase and the other formed a dispersed phase. The results of WAXD indicated that the crystal structures of PBS and PES were almost unchanged before and after blending, since the positions of characteristic diffraction peaks of both components remain almost unchanged.Graphical abstractCrystallization rate of PBS in the blends decreased first and then increased with increase in PES content, and that of PES increased steadily with increase in PBS content. The rich component formed a continuous phase and the other formed a dispersed phase of the blend. Crystal structures of PBS and PES were almost unchanged after blending with each other.Highlights► PBS/PES blend systems are partially miscible. ► Blending did not change the crystallization mechanisms of PBS and PES not affects the crystallization rates. ► The rich component formed the continuous phase while the poor component formed the dispersed phase of the blends. ► Crystal structures of PBS and PES were almost unchanged after blending with each other.
Co-reporter:Mei Zhang, Fei Song, Xiu-Li Wang, Yu-Zhong Wang
Colloids and Surfaces B: Biointerfaces 2012 100() pp: 16-21
Publication Date(Web):
DOI:10.1016/j.colsurfb.2012.05.031
Co-reporter:Gang Wu;Dr. Si-Chong Chen;Dr. Xiu-Li Wang;Dr. Ke-Ke Yang ; Yu-Zhong Wang
Chemistry - A European Journal 2012 Volume 18( Issue 39) pp:12237-12241
Publication Date(Web):
DOI:10.1002/chem.201103961
Co-reporter:Wei-cheng Xiong;Li Chen 陈力;De-yi Wang;Fei Song
Chinese Journal of Polymer Science 2012 Volume 30( Issue 1) pp:72-81
Publication Date(Web):2012 January
DOI:10.1007/s10118-012-1100-z
The synergistic effect of phosphorus oxynitride (PON) with a novolac-based char former modified by salification (NA-metal salt) on the flame retardance of polyamide 6 (PA6) was investigated. For this purpose, various flame-retardant PA6 systems were melt-compounded with PON, PON/NA, PON/NA-V2O5 and PON/NA-Fe2O3, and their flame retardance was evaluated by measuring the limiting oxygen index (LOI) values and UL-94 vertical burning ratings. The results showed that, compared with the PA6/PON/NA system, the combination of two char formers (NA-V2O5, NA-Fe2O3) with PON could obviously improve the char formation and flame retardance of PA6. The flame retardance and cone calorimetric analyses showed the stronger synergism as well as the better flame retardant performance of PON/NA-Fe2O3 flame retardant system. The effects of different char formers on the flame retardance and thermal stability of this system were also discussed.
Co-reporter:Cong Liu, Jian-Bing Zeng, Shao-Long Li, Yi-Song He, Yu-Zhong Wang
Polymer 2012 Volume 53(Issue 2) pp:481-489
Publication Date(Web):24 January 2012
DOI:10.1016/j.polymer.2011.12.003
Poly(ethylene glycol) (PEG) segments were incorporated into poly(ethylene succinate) (PES) by chain-extension reaction of PEG with PES using 1,6-hexamethylene diisocyanate as a chain-extender, forming a poly(ester ether urethane) (PEEU). The chemical structures and molecular weights of the PEEUs were determined by 1H NMR and GPC, respectively. The composition dependence of thermal transitions, crystallization, hydrophilicity, in vitro biocompatibility, in vitro biodegradation and tensile properties of the PEEUs were systematically investigated. The glass transition temperature and degree of crystallinity of PEEU decreased with increase of PEG content. The hydrophilicity increased with PEG content as proved by the decreased water contact angle and increased water absorption. The results of cell culturing suggested that the in vitro biocompatibility increased with PEG content. Hydrolytic degradation demonstrated that degradation rate of PEEU increased with PEG content, which was caused by the increased hydrophilicity and decreased degree of crystallinity with increase of PEG content. The tensile results proved that the tensile strength and modulus decreased while elongation at break increased with PEG content.
Co-reporter:Hong-Bing Chen, Li Chen, Xue Dong, Liang-Jie Li, Yu-Zhong Wang
Polymer 2012 Volume 53(Issue 16) pp:3520-3528
Publication Date(Web):19 July 2012
DOI:10.1016/j.polymer.2012.05.050
Phosphorus-containing flame-retardant monomer entitled 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phospha-phenanthrene-10-oxide (DDP) was first esterified with 1,3-propane diol, then incorporated in poly(trimethylene terephthalate) (PTT) chain via solid-state polymerization (SSP) at 200 °C. Reaction kinetics of incorporation was studied choosing 30 wt% DDP content as representative example. The reaction rate constant kf was calculated to be 1.68 h−1. The intrinsic viscosity increased with the increase of tssp, and decreased with the increase of DDP content. The sequence distribution of resulted copolyester was also analyzed with 1H NMR. Results suggested that all of the samples possess block chemical structure, and the degree of randomness increased with the increase of transesterification. For the transesterification reaction occurs only in amorphous phase of the material, the copolyester exhibited greater tendency to form block constitution when increasing DDP content. DSC investigation further confirmed the non-random constitution of the resulted copolyester.
Co-reporter:Jian-Bing Zeng, Yi-Song He, Shao-Long Li, and Yu-Zhong Wang
Biomacromolecules 2012 Volume 13(Issue 1) pp:
Publication Date(Web):December 12, 2011
DOI:10.1021/bm201564a
Chitin is the second most abundant semicrystalline polysaccharide. Like cellulose, the amorphous domains of chitin can also be removed under certain conditions such as acidolysis to give rise to crystallites in nanoscale, which are the so-called chitin nanocrystals or chitin whiskers (CHWs). CHW together with other organic nanoparticles such as cellulose whisker (CW) and starch nanocrystal show many advantages over traditional inorganic nanoparticles such as easy availability, nontoxicity, biodegradability, low density, and easy modification. They have been widely used as substitutes for inorganic nanoparticles in reinforcing polymer nanocomposites. The research and development of CHW related areas are much slower than those of CW. However, CHWs are still of strategic importance in the resource scarcity periods because of their abundant availability and special properties. During the past decade, increasing studies have been done on preparation of CHWs and their application in reinforcing polymer nanocomposites. Some other applications such as being used as feedstock to prepare chitosan nanoscaffolds have also been investigated. This Article is to review the recent development on CHW related studies.
Co-reporter:Si-Chong Chen, Gang Wu, Jing Shi and Yu-Zhong Wang
Chemical Communications 2011 vol. 47(Issue 14) pp:4198-4200
Publication Date(Web):02 Mar 2011
DOI:10.1039/C1CC00050K
Nano aggregates in aqueous medium with a novel “star anise”-like morphology were prepared from a branched alternating multi-block copolymer composed of 3-arm star-like hydrophobic poly(p-dioxanone) block and linear hydrophilic poly(ethylene glycol) block. The influence of block length on the morphology of the nano aggregate was investigated.
Co-reporter:Hong-Bing Chen, Li Chen, Yi Zhang, Jing-Jing Zhang and Yu-Zhong Wang
Physical Chemistry Chemical Physics 2011 vol. 13(Issue 23) pp:11067-11075
Publication Date(Web):12 May 2011
DOI:10.1039/C0CP02176H
A novel phosphorus-containing copolyester (PTTP), poly(trimethylene terephthalate) (PTT) copolyester with a bulky linking pendent group of 9,10-dihydro-10-[2,3-di(hydroxycarbonyl) propyl]-10-phosphaphenanthrene-10-oxide (DDP) was prepared, and its crystallization, crystal morphology and interference color were investigated in this article for the first time. Differential scanning calorimeter (DSC) results showed that with the increase of DDP content, the melting point (Tm) and crystallization ability of PTTP decreased. WAXD results suggests that the three samples share one crystal structure, however the crystallinity decreases with increasing DDP content. Polarized optical microscope (POM) observation indicated that the samples showed non-banded spherulites at a lower and higher temperature, and banded spherulites at the middle temperature range. From the micrographs obtained from scanning electronic microscopy (SEM) and atomic force microscopy (AFM), ringed patterns with many defects could be found for samples with higher DDP contents, which crystallized at a lower temperature, and a transformation from square-shaped spherulites to circular spherulites was noted for samples with higher DDP contents, which crystallized at a higher temperature. The interference color of the spherulites was also studied and it was shown that with the increase of film thickness or decrease of DDP content, the spherulites became more colorful under POM observation, indicating that the hindering effect and randomness caused by incorporating the DDP monomer with a bulky pendent group into the PTT molecular chain exhibited a negative influence on the molecular mobility and crystallization ability of the copolyester, and led to the formation of the defective band morphology and the less colorful interference color of the PTTP spherulites.
Co-reporter:Jian-Bing Zeng, Ling Jiao, Yi-Dong Li, Madhusudhan Srinivasan, Tao Li, Yu-Zhong Wang
Carbohydrate Polymers 2011 Volume 83(Issue 2) pp:762-768
Publication Date(Web):10 January 2011
DOI:10.1016/j.carbpol.2010.08.051
Poly(butylene succinate) (PBS) was blended with thermoplastic starch (TPS) to improve the mechanical properties and reduce water absorption of the resulting starch-based plastics. In order to enhance the miscibility between TPS and PBS, reactive PBS (RPBS) with terminal NCO group was synthesized first and then blended with TPS. The mechanical properties of the TPS were greatly improved after blending with RPBS, the tensile strength was increased to 10 times more than TPS even only 10 wt% RPBS was introduced. The water absorption of the blend was significantly reduced with increasing RPBS content. SEM results suggest RPBS to be uniformly distributed in the TPS matrix, and the size of the RPBS phase was decreased with reducing intrinsic viscosity of RPBS. The study of contact angle indicated that the hydrophobicity of the blend was largely enhanced toward TPS. With improved mechanical properties and reduced water absorption, the materials could find more extensive applications.
Co-reporter:Fei Song, Xiu-Li Wang, Yu-Zhong Wang
European Polymer Journal 2011 Volume 47(Issue 10) pp:1885-1892
Publication Date(Web):October 2011
DOI:10.1016/j.eurpolymj.2011.07.023
To fulfill the development of biotechnology and biomedicine, environmental-responsive polymer materials are wanted for isolation and purification of biomolecules. Herein, a novel thermo-responsive poly(methyl methacrylate) (PMMA)/poly(N-isopropylacrylamide) (PNIPAM) blend nanofibrous mat was developed, which can adsorb and release a model solute, bovine serum albumin (BSA), through the way of hydrophilicity–hydrophobicity transition behavior of PNIPAM. The uniform bead-free electrospun nanofibers were obtained from the homogeneous PMMA solution in the presence of different amount of PNIPAM. Scanning electron microscopy (SEM) analysis showed that the electrospinnability of PMMA was improved by the addition of PNIPAM, and the diameter of resultant nanofibers could be modulated by controlling the amount of PNIPAM. The thermo-responsive swelling behavior of the blend nanofibrous mats was reversible and reproducible by changing environmental temperature across the lower critical solution temperature (LCST) of PNIPAM. Moreover, the separation property of the blend nanofibrous mats was found to be related to the amount of PNIPAM as well as the concentration of BSA. As for a better separation effect, the nanofibers with higher content of PNIPAM were favorable.Graphical abstractHighlights► PMMA/PNIPAM nanofibers were developed and their diameters could be controlled. ► The nanofibrous mats showed thermo-responsive swelling behaviors. ► Protein adsorption/release property could be tuned by the PNIPAM amount of the mats.
Co-reporter:Xue-Qi Liu, De-Yi Wang, Xiu-Li Wang, Li Chen, Yu-Zhong Wang
Polymer Degradation and Stability 2011 Volume 96(Issue 5) pp:771-777
Publication Date(Web):May 2011
DOI:10.1016/j.polymdegradstab.2011.02.022
Novel intumescent flame-retardant poly(lactic acid) (PLA/IFR)/organo-modified α-zirconium phosphate(OZrP) nanocomposites were prepared via incorporation of charring agent (CA), ammonium polyphosphate (APP) and OZrP into PLA. OZrP was synthesized directly by a solvent thermal method. The morphological characterization of PLA/IFR/OZrP nanocomposites was conducted by wide angle X-ray diffraction (WXRD) and transmission electron microscopy (TEM). The effect of the OZrP on flame retardancy and the thermal stability of PLA/IFR composites were studied by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter test. The TGA data illustrated that the OZrP could increase the residue and significantly improve the flame retardancy of PLA/IFR/OZrP nanocomposites showing an excellent synergistic effect. The addition of OZrP to the flame-retardant PLA increases the LOI and enhances the UL-94 rating. Cone calorimeter tests gave clear evidence that the incorporation of OZrP into PLA/IFR composites resulted in the significant reduction of the heat release rate (HRR), low total heat release (THR) and high amount of char residues during combustion. The flame-retardant mechanism of PLA/IFR/OZrP nanocomposites may correspond to the intumescent flame-retardant mechanism and catalyzed carbonization mechanism caused by OZrP.
Co-reporter:Hong-Bing Chen, Xiu-Li Wang, Jian-Bing Zeng, Ling-Ling Li, Feng-Xia Dong, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2011 Volume 50(Issue 4) pp:2065-2072
Publication Date(Web):January 24, 2011
DOI:10.1021/ie101798n
A novel multiblock poly(ester urethane) (PBESTU) was synthesized through chain-extension reaction of hydroxyl-terminated poly(butylene succinate) (PBS−OH) and poly(ethylene succinate-co-ethylene terephthalate) (PETS−OH), using toluene-2,4-diisocyanate (TDI) as chain extender. The chemical structure and molecular weight of PBESTUs were characterized by 1H NMR, intrinsic viscosity, and GPC. The thermal behaviors were investigated by DSC and TGA. The resulting copolymers, PBESTUs, have a sole glass transition temperature (Tg), which indicated that the two segments, PETS and PBS, were well compatible in the amorphous phase. PETS segment enhanced the thermal degradation temperature of PBESTUs. The DSC and WAXD results showed that PBS segment made great contribution to the crystallization of PBESTUs. PBESTUs possessed excellent mechanical properties according to tensile testing.
Co-reporter:Yun Liu, Jing Zhao, Cheng-Liang Deng, Li Chen, De-Yi Wang, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2011 Volume 50(Issue 4) pp:2047-2054
Publication Date(Web):January 11, 2011
DOI:10.1021/ie101737n
Intumescent flame-retardant polypropylene-containing phosphorus and nitrogen compounds were enhanced significantly by adding a small amount of sepiolite as a synergistic agent. The flame-retardant polypropylene composite was characterized by limiting oxygen index (LOI), UL-94, the cone calorimeter (CCT), and thermogravimetric analysis (TGA) to study the combustion behavior and thermal stability. The addition of 0.5% sepiolite increased the LOI from 29.8 to 31.8. The addition of sepiolite at a low additive amount appears to be an optimum blend ratio for the low heat release rate, total smoke, and CO2 production. Sepiolite also has a significant improvement in mechanical properties.
Co-reporter:Jian-Bing Zeng, Madhusudhan Srinivansan, Shao-Long Li, Ramani Narayan, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2011 Volume 50(Issue 8) pp:4471-4477
Publication Date(Web):March 11, 2011
DOI:10.1021/ie102299y
Nonisothermal and isothermal cold crystallization behaviors of poly(p-dioxanone) (PPDO) were investigated by differential scanning calorimetry (DSC). There were two crystallization exotherms—a major exotherm between 25 °C and 50 °C and a minor one almost unchanged at 77 °C with various heating rates—in the heating scans of PPDO during nonisothermal cold crystallization. Temperature-modulated differential scanning calorimetry (TMDSC) revealed the major crystallization exotherm in the low-temperature range to be the real cold crystallization peak, and the minor one in the high-temperature range to be the melt-recrystallization peak of crystals with lower thermal stability. Several methods, including the Avrami, Tobin, and Ozawa equations, were employed to analyze the nonisothermal cold crystallization kinetics of PPDO. The efficiencies of the Avrami and Tobin methods were compared, and the results suggest that the Avrami equation is more suitable for describing nonisothermal cold crystallization kinetics of PPDO. The activation energy for nonisothermal cold crystallization of PPDO was calculated to be 35.27 kJ/mol, using the Kissinger method. In addition, the Avrami equation was also used to describe the isothermal cold crystallization kinetics of PPDO.
Co-reporter:Jian-Bing Zeng, Yi-Dong Li, Yi-Song He, Shao-Long Li, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2011 Volume 50(Issue 10) pp:6124-6131
Publication Date(Web):March 31, 2011
DOI:10.1021/ie102422q
Poly(l-lactide) (PLLA) is one of the most promising biobased and biodegradable polymers. However, the lack of toughness restricts its application considerably. In the present study, PLLA was successfully toughened by blending with a poly(lactic acid) based poly(ester-urethane) (PEU), which contained poly(butylene succinate) as a flexible segment. The tensile properties and notched Izod impact strength of PLLA and toughened PLLA were investigated. The flexibility of PLLA was considerably improved after introduction of PEU by the evidence of high strain and improved impact strength. The crystallization behavior was investigated by differential scanning calorimeter (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). The glass transition temperature of toughened PLLA decreased with an increasing content of PEU, suggesting that the blends showed limited miscibility. POM observation showed that the crystallites of PEU uniformly distributed in the PLLA matrix after two-step crystallization at 120 and 60 °C. The results of WAXD suggest that the crystal structure of PLLA remained unchanged after blending with the PEU.
Co-reporter:Jing Ding, Si-Chong Chen, Xiu-Li Wang, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2011 Volume 50(Issue 15) pp:9123-9130
Publication Date(Web):June 22, 2011
DOI:10.1021/ie2003889
A thermoplastic modified poly(vinyl alcohol) (PVA-g-LA) with improved melt processing property was prepared by melt polycondensation of PVA with lactic acid. Rheological behaviors of PVA-g-LA copolymers were investigated using a high-pressure capillary rheometer. The influences of the content of oligo-poly (lactic acid) graft chains and content of PVA-0588 on the rheological properties of PVA-g-LA copolymers were researched. The rheological parameters including non-Newtonian index and the viscous flow activation energy were analyzed and evaluated. As predicted, the PVA-g-LA samples exhibited noticeable shear thinning behavior. The apparent viscosity, the viscous flow activation energy, and the non-Newtonian index of PVA-g-LA showed obvious correlation with the PLA grafting chain content and PVA-0588 content at a constant temperature and shear rate. Both the increase of the content of oligo-PLA graft chains and content of PVA-0588 with PVA-1799 can improve the melting flow processing of PVA-g-LA copolymer.
Co-reporter:Xiao-Ya Yuan, De-Yi Wang, Li Chen, Xiu-Li Wang, Yu-Zhong Wang
Polymer Degradation and Stability 2011 Volume 96(Issue 9) pp:1669-1675
Publication Date(Web):September 2011
DOI:10.1016/j.polymdegradstab.2011.06.012
The molecular design for inherently flame-retardant poly(lactic acid) (IFR-PLA) was outlined and achieved by chemically incorporating an effective organophophorus-type flame retardant (FR) into the PLA backbone via the chain extension of the dihydroxyl-terminated prepolymer with 1, 6-hexamethylene diisocyanate (HDI). The structure of IFR-PLA was characterized by 1H- and 31P-nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. IFR-PLA was further blended with the commercial PLA to prepare flame retardant PLA blends (PLA-FR blend). The relevant properties of IFR-PLA and PLA-FR blends were evaluated by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), limiting oxygen index (LOI) measurements and UL-94 tests. The thermal analysis revealed that the char yield of IFR-PLA and PLA-FR blend above 400 °C was greatly enhanced compared to that of pure PLA. The LOI value was significantly improved from 19 for pure PLA to 29 when 1 wt% of phosphorus content was introduced and all IFR-PLA samples achieved V-0 rating in the UL-94 tests. PLA-FR blends had an LOI value of 25–26 and UL-94 V-2 rating at 20 wt% of IFR-PLA content. The tensile strength of all the FR PLA systems was ca. 60 MPa. The method used in this study provided a novel route to permanently flame retard PLA.
Co-reporter:Lian-Lian Wei, De-Yi Wang, Hong-Bing Chen, Li Chen, Xiu-Li Wang, Yu-Zhong Wang
Polymer Degradation and Stability 2011 Volume 96(Issue 9) pp:1557-1561
Publication Date(Web):September 2011
DOI:10.1016/j.polymdegradstab.2011.05.018
An aryl polyphenylphosphonate, poly(9-oxa-10-(2,5-dihydro-xyphenyl) phospha-phenanthrene-10-oxide) phenylphosphonate (WLA-3), was used to prepare a flame-retardant poly(lactic acid) (PLA) by direct melt compounding. The thermal behaviour, burning behaviour and mechanical properties of the flame-retardant PLA systems have been investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), vertical burning test (UL-94), limiting oxygen index (LOI), cone calorimeter test (CCT) and tensile test. The flame retardance mechanism has been studied via Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and P content analysis. The UL-94 ratings of PLA’s containing 7phr (W7P) and 10phr (W10P) of WLA-3 were enhanced to V-0 from no rating for neat PLA. However, the cone calorimetry of flame-retardant PLA (W7P) only showed a little decrease in heat release rate (HRR), peak of heat release rate (PHRR) and total heat release (THR) compared to neat PLA. TGA results showed that the PLA containing different amounts of WLA-3 presented more complicated thermal decomposition behaviours than neat PLA. Additionally, the results from DSC and tensile tests showed that the addition of WLA-3 into PLA had a slight impact on the crystallization behaviours and tensile properties.
Co-reporter:Zhi Hu, Li Chen, Gong-Peng Lin, Yuan Luo, Yu-Zhong Wang
Polymer Degradation and Stability 2011 Volume 96(Issue 9) pp:1538-1545
Publication Date(Web):September 2011
DOI:10.1016/j.polymdegradstab.2011.03.010
Aluminum salts of phosphinic acid mixture of diisobutylphosphinic acid and monoisobutylphosphinic acid (HPA-2TBA-Al) and glass fibres were compounded with polyamide 6 to prepare a series of flame retardant GF/PA6 composites via melt blending. The flame retardance and burning behaviors of the composites were investigated by limiting oxygen index (LOI), vertical burning test (UL-94), and Cone calorimeter test. The thermal properties and decomposition kinetics were investigated by thermogravimetric analysis (TGA) under N2 atmosphere. Addition of HPA-2TBA-Al results in an increased LOI value, a UL-94 V-0 rating together with a decrease in both the values of PHRR and THR in Cone calorimetric analysis. Visual observations and scanning electronic microscopy (SEM) after flame retardant tests confirmed the char-formation which acts as a fire barrier in condense phase. Analysis of cone calorimeter data indicates that gas phase flame retardant mechanism exists in the GFPA6/HPA-2TBA-Al system.
Co-reporter:Yun Liu, Cheng-Liang Deng, Jing Zhao, Jun-Sheng Wang, Li Chen, Yu-Zhong Wang
Polymer Degradation and Stability 2011 Volume 96(Issue 3) pp:363-370
Publication Date(Web):March 2011
DOI:10.1016/j.polymdegradstab.2010.02.033
In order to solve the “candlewick effect” caused by glass fibers, which results in the decrease of flame retardancy of flame-retardant long-glass-fiber-reinforced polypropylene (LGFPP) systems, and the deterioration of mechanical properties caused by adding an additional amount of flame retardants compared with flame-retardant non-glass-fiber-reinforced polypropylene systems so as to keep a same flame retardancy, a novel intumescent flame retardant (IFR) system, which is composed of a charring agent (CA), ammonium polyphosphate (APP) and organically-modified montmorillonite (OMMT), was used to flame retard LGFPP. The thermal stability, combustion behavior, char formation, flame retardant mechanism and mechanical properties of the IFR-LGFPP samples were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 test, cone calorimeter test, scanning electronic microscopy, and mechanical property tests. When the content of IFR is 20 wt%, the LOI value of IFR-LGFPP reaches 31.3, and the vertical burning test reaches UL-94 V-0 rating, solving the “candlewick effect” caused by long glass fiber without additional amount of the IFR. All the relevant cone calorimeter parameters also show that IFR-LGFPP has much better flame-retardant behaviors than LGFPP. Furthermore, the mechanical properties of IFR-LGFPP almost remain unchanged in comparison with those of LGFPP containing no IFR. The flame retardant mechanism was also discussed.
Co-reporter:Zhi Hu, Li Chen, Bin Zhao, Yuan Luo, De-Yi Wang, Yu-Zhong Wang
Polymer Degradation and Stability 2011 Volume 96(Issue 3) pp:320-327
Publication Date(Web):March 2011
DOI:10.1016/j.polymdegradstab.2010.03.005
A novel silicon- and phosphorus-containing flame retardant, poly (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide siloxane), P(DOPO-VTES) was synthesized from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO) and vinyltriethoxy silane(VTES). Its chemical structure was confirmed by FTIR. The thermal gravimetrical analysis (TGA) showed that P(DOPO-VTES) had good thermal stability and a high of char yield (86.31%) at 700 °C in nitrogen atmosphere. Its XRD patterns showed that this compound had a certain ordered structure. P(DOPO-VTES) was blended with polycarbonate (PC) together with montmorillonite(MMT) to prepare a series of organic-inorganic hybrids of flame retardant (PC)/P(DOPO-VTES)/MMT via melt blending. The thermal degradation behavior and flame retardancy of those hybrids were investigated with TGA, limiting oxygen index (LOI), vertical burning test (UL-94), and cone calorimeter. The LOI value of the flame-retardant PC systems could reach a maximal value of 32.8 when the content of P(DOPO-VTES) was 5 wt%. When 2 wt% MMT was added into the PC/5%P(DOPO-VTES) system, the UL-94 rating reached V-0. The possible flame retardant mode of MMT was studied via the dynamic rheological properties of the systems and the morphology of the chars remaining after the LOI test and the cone calorimeter test.
Co-reporter:Bin Zhao;Zhi Hu;Li Chen;Yun Liu;Ya Liu
Journal of Applied Polymer Science 2011 Volume 119( Issue 4) pp:2379-2385
Publication Date(Web):
DOI:10.1002/app.32860
Abstract
A novel inorganic compound, aluminum hypophosphite (AP), was synthesized successfully and applied as a flame retardant to glass-fiber-reinforced polyamide 6 (GF–PA6). The thermal stability and burning behaviors of the GF–PA6 samples containing AP (flame-retardant GF–PA6) were investigated by thermogravimetric analysis, vertical burning testing (with a UL-94 instrument), limiting oxygen index (LOI) testing, and cone calorimeter testing (CCT). The thermogravimetric data indicated that the addition of AP decreased the onset decomposition temperatures, the maximum mass loss rate (MLR), and the maximum-rate decomposition temperature of GF–PA6 and increased the residue chars of the samples. Compared with the neat GF–PA6, the AP-containing GF–PA6 samples had obviously improved flame retardancy: the LOI value increased from 22.5 to 30.1, and the UL-94 rating went from no rating to V-0 (1.6 mm) when the AP content increased from 0 to 25 wt % in GF–PA6. The results of CCT reveal that the heat release rate, total heat release, and MLR of the AP-containing GF–PA6 samples were lower than those of GF–PA6. Furthermore, the higher additive amount of AP affected the mechanical properties of GF–PA6, but they remained acceptable. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Juan Yang;Chao-Xian Wang;Zhi-Sheng Yu;Yang Li;Ke-Ke Yang
Journal of Applied Polymer Science 2011 Volume 121( Issue 4) pp:2458-2466
Publication Date(Web):
DOI:10.1002/app.33773
Abstract
A novel toughening modifier, styrene–isoprene–butadiene rubber (SIBR), was used to improve the impact resistance and toughness of acrylonitrile–butadiene–styrene (ABS) resin via bulk polymerization. For comparison, two kinds of ABS samples were prepared: ABS-1 was toughened by a conventional modifier (a low-cis polybutadiene rubber/styrene–butadiene block copolymer), and ABS-2 was toughened by SIBR. The mechanical properties, microstructures of the as-prepared materials, and fracture surface morphology of the specimens after impact were studied by instrumented notched Izod impact tests and tensile tests, transmission electron microscopy, and scanning electron microscopy, respectively. The mechanical test results show that ABS-2 had a much higher impact strength and elongation at break than ABS-1. The microscopic results suggested that fracture resistance of ABS-1 only depended on voids, shear yielding, and few crazing, which resulted in less ductile fracture behavior. Compared with ABS-1, ABS toughened by linear random SIBR (ABS-2) displayed the synergistic toughening effect of crazing and shear yielding, which could absorb and dissipate massive energy, and presented high ductile fracture behavior. These results were also confirmed by instrumented impact tests. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Yun-Xuan Weng, Xiu-Li Wang, Yu-Zhong Wang
Polymer Testing 2011 Volume 30(Issue 4) pp:372-380
Publication Date(Web):June 2011
DOI:10.1016/j.polymertesting.2011.02.001
Polyhydroxyalkanotes (PHAs) are biobased and biodegradable polymers, of which poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV, 3 %mol HV) and poly-3-hydroxybutyrate-co-4-hydroxybutyrate [P(3HB,4HB), 10 %mol 4HB] are currently commercialized. To understand the influence of chemical structure on the biodegradability of PHA, the biodegradation behavior of poly(hydroxybutyrate) (PHB), PHBV (40 %mol HV), PHBV (20 %mol HV), PHBV (3 %mol HV) and P(3HB,4HB) (10 %mol 4HB) were investigated under the controlled composting conditions according to ISO 14855-1. It was found that PHAs with different chemical structures can be biodegraded under the controlled composting conditions. The order of biodegradability was P(3HB, 4HB) (40 %mol 4HB) ≈ PHBV(40 %mol HV) >PHBV(20 %mol HV) >PHBV(3 %mol HV) >PHB.
Co-reporter:De-Yi Wang, Yan-Peng Song, Ling Lin, Xiu-Li Wang, Yu-Zhong Wang
Polymer 2011 Volume 52(Issue 2) pp:233-238
Publication Date(Web):21 January 2011
DOI:10.1016/j.polymer.2010.11.023
An inherently flame-retardant poly(lactic acid) (PLA) was synthesized via the chain-extending reactions of dihydroxyl terminated pre-poly(lactic acid) (pre-PLA), which was synthesized by direct polycondensation of l-lactic acid using 1,4-butanediol as initiator and stannous chloride (SnCl2) as catalyst, using ethyl phosphorodichloridate as chain extender. The resulting phosphorus-containing poly(lactic acid) (PPLA) was characterized by gel permeation chromatography (GPC), 1H and 31P nuclear magnetic resonance (1H, 31P NMR) and homonuclear correlation spectroscopy (COSY) and inductively coupled plasma-mass (ICP). A comprehensive flame retardant property of PPLA was evaluated by microscale combustion calorimetry (MCC), limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter test (CCT). PPLA has excellent flame retardancy and also can be used as a flame retardant for commercial PLA. Only 5 wt.% of PPLA added into PLA can obtain good flame retardant properties. As the content of PPLA is further increased to 10 wt.%, PLA can have much better flame retardancy (LOI = 35 and UL-94 V-0 rating), lower peak heat release rate (pHRR) and longer ignition time (TTI) than neat PLA. All those results mean that this novel approach to impart flame retardancy to PLA is very effective.
Co-reporter:Gang Wu, Si-Chong Chen, Qi Zhan, and Yu-Zhong Wang
Macromolecules 2011 Volume 44(Issue 4) pp:999-1008
Publication Date(Web):January 25, 2011
DOI:10.1021/ma102588k
As an extremely promising characteristic, the transformation between a lower critical solution temperature (LCST) and an upper critical solution temperature (UCST) has rarely been reported until now. In the present paper, a three-step strategy, based on “grafting onto” concept, was implemented to synthesize a novel thermoresponsive amphiphilic biodegradable and biocompatible poly(p-dioxanone)-grafted poly(vinyl alcohol) (PVA-g-PPDO) copolymer with well-define structure. A transformable thermoresponsivity from a LCST to an UCST can be achieved facilely via changing the graft chain length of the resulting PVA-g-PPDO copolymers. The results of transmittance indicate that a wide range of LCST and UCST between 30 and 80 °C can be achieved easily, which is attributed to the controllable structures and hydrophobic/hydrophilic ratio of copolymers by adjusting degree of polymerization (Dp) of PPDO prepolymers and molar feed ratios in the last esterification coupling step. This is the first example having the feature of architecture-determined different-type thermoresponsivities by a facile change of side chain length from an identical comb-like graft copolymer family, and displaying a wide range of controllable LCST and UCST. The influence of solution concentrations on thermoresponsivities has been investigated by UV−vis spectrometer, and the solution properties of copolymers have also been evaluated by dynamic light scattering (DLS). The results show that the self-assembly of copolymers displaying different thermoresponsivities can be observed and regulated by changing the structure and temperature.
Co-reporter:Fei Song, Xiu-Li Wang, Yu-Zhong Wang
Colloids and Surfaces B: Biointerfaces 2011 Volume 88(Issue 2) pp:749-754
Publication Date(Web):1 December 2011
DOI:10.1016/j.colsurfb.2011.08.015
A facile electrospinning method has been utilized to fabricate poly (N-isopropylacrylamide) (PNIPAM)/poly (ethylene oxide) (PEO) blend nanofibers having the mean fiber diameters from approximately 250 to 380 nm. Scanning electron microscopy (SEM) images showed that the morphology and diameter distribution of the nanofibrous scaffolds can be easily modulated by changing the weight ratio of PNIPAM/PEO in electrospinning solution. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) demonstrated that there were interactions between the molecules of PNIPAM and PEO. Vitamin B12 was chosen as a hydrophilic model drug for in situ encapsulation in PNIPAM/PEO blend nanofibrous scaffolds. The rate of drug release can be controlled by adjusting the weight ratio of PNIPAM/PEO, the temperature of release medium and the drug loading amount. It is suggested that the blend nanofibrous scaffold could be used as a new thermo-responsive matrix for the entrapment and controlled release of drugs.Graphical abstractFabrication of PNIPAM/PEO nanofibrous scaffold and its in vitro thermo-responsive drug release property.Highlights► A new thermo-responsive nanofibrous scaffold for drug delivery. ► Adjustable diameter for PNIPAM/PEO nanofibers. ► In situ drug encapsulation and high drug loading property. ► Controlled drug release rate by chemical composition of nanofiber as well as drug loading.
Co-reporter:Fei Song, Dao-Lu Tang, Xiu-Li Wang, and Yu-Zhong Wang
Biomacromolecules 2011 Volume 12(Issue 10) pp:
Publication Date(Web):September 13, 2011
DOI:10.1021/bm200904x
Recently, there is an increasing interest of using bio-based polymers instead of conventional petroleum-based polymers to fabricate biodegradable materials. Soy protein isolate (SPI), a protein with reproducible resource, good biocompatibility, biodegradability, and processability, has a significant potential in the food industry, agriculture, bioscience, and biotechnology. Up to now, several technologies have been applied to prepare SPI-based materials with equivalent or superior physical and mechanical properties compared with petroleum-based materials. The aim of this review is focused on discussion of the advantages and limitations of native SPI as well as the bulk and surface modification strategies for SPI. Moreover, some applications of SPI-based materials, especially for food preservation and packaging technology, were discussed.
Co-reporter:Rong Yang, Li Chen, Wen-Qiang Zhang, Hong-Bing Chen, Yu-Zhong Wang
Polymer 2011 Volume 52(Issue 18) pp:4150-4157
Publication Date(Web):18 August 2011
DOI:10.1016/j.polymer.2011.06.047
Polycarbonate (PC) was blended with various loadings of novel phosphorus-containing thermotropic liquid crystalline copolyester named PHDDT to form the in situ reinforced composites (PC/PHDDT) by flake extrusion. The morphology, thermal behaviors, tensile properties and flame-retardant performances of PC/PHDDT composites were investigated. Results suggested that fine deformation and microfibrillation of PHDDT in PC matrix could be formed during flake extrusion, which was confirmed by both the SEM observation and rheological analysis. With the increase of PHDDT content, the limiting oxygen index (LOI), tensile strength and storage modulus of the composites were enhanced simultaneously, along with the gradually decreased values of the peak heat release rate (PHRR) and the total heat released (THR), indicating the in situ reinforced and flame-retardant PC/PHDDT composites could be obtained.
Co-reporter:Feng Chen, Si-Chong Chen, Ke-Ke Yang, Xiu-Li Wang, Yu-Zhong Wang
European Polymer Journal 2010 Volume 46(Issue 1) pp:24-33
Publication Date(Web):January 2010
DOI:10.1016/j.eurpolymj.2009.09.008
Long-chain-branched poly(p-dioxanone)s (LCB-PPDOs) with different branch densities were prepared via the chain-extending reaction of hydroxyl group terminated linear bi-functional PPDO (2a-PPDO) and star-like tri-functional PPDO (3a-PPDO) prepolymers, which were synthesized by the ring-opening polymerization of p-dioxanone (PDO) using 1,4-butanediol (BD) and trimethylolpropane (TMP) as multi-functional initiators, respectively. The undesirable gelation was successfully depressed by adjusting the chain length and feed ratio of prepolymers. The average molecular weight between branch points (Mb) and the average number of branch per 100,000 g/mol (Bn) of LCB-PPDOs were calculated from the 1H NMR spectra. The average number of branch ranged from 0 to 6.72 branch points per 100,000 g/mol, and the number-average molecular weights between branch points ranged from 6900 to 20,500 g/mol. The results of differential scanning calorimetry (DSC) showed that the crystallization behavior of LCB-PPDOs was changed evidently with the branch density. Small-amplitude dynamic oscillatory rheometer was used to investigate the rheological properties of the melts of LCB-PPDO including zero-shear viscosity, storage modulus, relaxation times and loss angle, which largely depended on the branch density and length of LCB-PPDOs. Therefore, the rheological behaviors of PPDO can be well-controlled via synthesizing LCB-PPDOs with the desired architectures.Long-chain-branched poly(p-dioxanone) was prepared by using hexamethylene diisocyanate as chain-extender of bi- and tri-functional PPDO prepolymers. The undesired gelation was depressed by adjusting the molecular weight and content of the prepolymer.
Co-reporter:Jing Zhang, Qian Zhou, Xian-Hong Jiang, An-Ke Du, Tao Zhao, Johannes van Kasteren, Yu-Zhong Wang
Polymer Degradation and Stability 2010 Volume 95(Issue 6) pp:1077-1082
Publication Date(Web):June 2010
DOI:10.1016/j.polymdegradstab.2010.02.028
A catalytic system based on Na2WO4/CH3COOH/H2O2 effectively oxidizes natural rubber (NR) to prepare telechelic epoxidised liquid natural rubber (TELNR). The Na2WO4/CH3COOH/H2O2 catalytic system possesses a much higher epoxidation efficiency than the traditional CH3COOH/H2O2 system: the epoxidation degree (Xepoxy) of products increases from merely 5.6% (CH3COOH/H2O2) to values as high as 52.1% (Na2WO4/CH3COOH/H2O2) by reacting for 24 h at 60 °C. Moreover, this catalytic system also induces hydrolytic degradation so that the weight average molecular weight (Mw¯) of NR decreases, e.g., from 14.10 × 105 Da (NR) to 0.57 × 105 Da (TELNR) after reacting for 30 h.The catalytic process probably proceeds via a mononuclear tungsten peroxo-species with coordinated peracetyl/acetyl group, as suggested by ESI-MS measurements. During oxidation, the tungstic anion [W(CH3COOO)(O)(O2)2]− not only catalyzes NR epoxidation, but also induces a further oxidation of epoxy groups to form ketones and aldehydes.
Co-reporter:Chen-Hao Ke, Juan Li, Ke-Yi Fang, Qi-Liang Zhu, Jin Zhu, Qing Yan, Yu-Zhong Wang
Polymer Degradation and Stability 2010 Volume 95(Issue 5) pp:763-770
Publication Date(Web):May 2010
DOI:10.1016/j.polymdegradstab.2010.02.011
A novel hyperbranched polyamine charring agent (HPCA), a derivative of triazines, was synthesized and well characterized by 1H NMR and FTIR. HPCA and ammonium polyphosphate (APP) were added into polylactide (PLA) resin as an intumescent flame retardant (IFR) system to impart flame retardancy and dripping resistance to PLA. The flammability and thermal stability of IFR-PLA composites were investigated by limiting oxygen index (LOI), UL-94 vertical burning, cone calorimetry and thermogravometric analysis (TGA) tests. The results showed that the IFR system had both excellent flame retardant and anti-dripping abilities for PLA. The TGA curves suggested that HPCA has good ability of char formation and when combined with APP, would induce synergistic effect which could be clearly observed. This effect greatly promoted the char formation of IFR-PLA composites, hence improved the flame retardant property. Additionally, the structure and morphology of char residues were studied by XPS, FTIR and SEM.
Co-reporter:Hong-Bing Chen, Yi Zhang, Li Chen, Zhu-Bao Shao, Ya Liu and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 15) pp:7052-7059
Publication Date(Web):July 2, 2010
DOI:10.1021/ie1006917
A novel phosphorus-containing copolyester, poly(trimethylene terephthalate)-co-poly(trimethylene DDP)s (PTTP), was synthesized through esterification and polycondensation of terephthalic acid (TPA), 1,3-propane diol (PDO), and 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phospha-phenanthrene-10-oxide (DDP). The analysis of phosphorus content and the test of intrinsic viscosity indicated that DDP was successfully introduced to the poly(trimethylene terephthalate) (PTT) chain. The chemical structure of the resulting copolyesters was further confirmed by 1H NMR and 31P NMR. The thermal behaviors were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and it was shown that the introduction of DDP lowered the melting temperature and crystallization because of its bulky pendent groups and decreased the initial decomposition temperature in the nitrogen atmosphere due to its weak P−C bond. The flame retardant properties of the resulting copolyesters were characterized by limiting oxygen index (LOI) and cone calorimeter, and it was shown that the copolyesters had good inherent flame retardancy.
Co-reporter:Jun-Sheng Wang, Hai-Bo Zhao, Xin-Guo Ge, Yun Liu, Li Chen, De-Yi Wang and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 9) pp:4190-4196
Publication Date(Web):April 1, 2010
DOI:10.1021/ie100057n
A series of novel branched polyester-based ionomers were synthesized with trihydroxy ethyl esters of trimethyl-1,3,5-benzentricarboxylate (as branching agent) and sodium salt of 2-hydroxyethyl 3-(phenylphosphinyl)propionate (SHPPP, as end-capping agent) by melt polycondensation. The chemical structures of the branched polyester-based ionomers were confirmed with 1H and 31P NMR spectra. The effects of branching and ionic end groups on the melt behavior and thermal properties were investigated by differential scanning calorimetry and thermogravimetric analysis. The flammability and fire behavior were characterized by limiting oxygen index (LOI) and cone calorimeter. The LOI values of branched poly(ethylene terephthalate)s (PETs) are higher than that of pure PET. The cone calorimeter parameters of the samples such as heat release rate, total heat release, and time to ignition indicate that the fire safety of branched polyester-based ionomers is improved by introducing SHPPP. The effects of SHPPP on accelerating char forming and antidripping could be observed clearly from the pictures of the samples after LOI test.
Co-reporter:Zhu Xiong, Jian-Bing Zeng, Xiu-Li Wang, Yu-Rong Zhang, Ling-Ling Li and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 13) pp:5986-5992
Publication Date(Web):June 10, 2010
DOI:10.1021/ie100817h
Poly (l-lactic acid) (PLLA) is a biobased polymer, and poly(trimethylene terephthalate) (PTT) is a semibiobased polymer. However, PLLA is biodegradable, and PTT is not. In this paper, their copolymers (PTHT−PLLA) are synthesized via chain-extension reaction of hydroxyl terminated poly(trimethylene-co-hexamethylene terephthalate) (PTHT−OH) and hydroxyl terminated poly(l-lactic acid) (PLLA−OH) using toluene-2,4-diisocyanate (TDI) as a chain extender. The structures and molecular weights of PTHT−OH, PLLA−OH, and PTHT−PLLA were characterized by Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC). The thermal, crystalline, and mechanical properties of PTHT−PLLA were further studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and tensile testing. The resulting PTHT−PLLA copolyesters went through a two-stage thermal decomposition behavior and showed two glass transition temperatures. The tensile testing results showed that PTHT−PLLA copolyesters have excellent flexibility with a strain of more than 300%, which is much higher than that of PLLA. The copolyesters are expected to have a better biodegradability than PTT.
Co-reporter:Jian-Bing Zeng, Cong Liu, Fang-Yang Liu, Yi-Dong Li, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 20) pp:9870
Publication Date(Web):September 27, 2010
DOI:10.1021/ie101444x
Miscibility and crystallization behaviors of poly(butylenes succinate) (PBS) and poly(l-lactic acid) (PLLA) segments in their multiblock copoly(ester urethane) were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). The single glass transition and depressed crystallization temperatures of PEUs with different compositions suggest that PBS and PLLA segments are miscible in amorphous phase of PEUs. Nonisothermal crystallization kinetics of PEUs was studied by Avrami and Mo methods; both results suggest that the crystallization rates of PEUs decreased with increasing weight fraction of PLLA segments. POM results indicate that banded spherulites were formed for PEUs when PLLA segments were introduced, and the band spacing increased with weight fraction of PLLA segments. The investigation of WAXD demonstrated the crystal structure of PEUs was the same as that of PBS, suggesting the crystallization of PEUs arose from PBS segments, and PLLA segments were unable to crystallize in PEUs.
Co-reporter:Jun Li, Zhi-Qiang Jiang, Jian Zhou, Ji Liu, Wen-Tao Shi, Qun Gu, and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 20) pp:9803
Publication Date(Web):September 10, 2010
DOI:10.1021/ie100915y
Aromatic−aliphatic copolyesters of poly(ethylene-co-diethylene terephthalate)-co-poly(l-lactic acid) (PEDLT) with different compositions were synthesized by direct melt copolyesterization of l-lactic acid oligomers and poly(ethylene-co-diethylene terephthalate) (PEDT) oligomers. Chemical structures, thermal properties, and crystalline behaviors were studied. 1H NMR confirmed that the short lactyl units were incorporated into the PEDT chains. Thermogravimetric analysis showed that PEDLT copolyesters were thermally stable up to about 380 °C. Both wide-angle X-ray diffraction and Fourier transform infrared spectroscopy showed that no poly(l-lactic acid) crystal was formed during the crystallization of PEDLT copolyesters. Isothermal crystallization of PEDLT copolyesters was carried out, and it was found that both the crystallinity and crystal growth rate decreased after incorporation of lactyl units compared with those of PEDT. The obtained aromatic−aliphatic copolyesters are expected to find a potential application as biodegradable polymer materials.
Co-reporter:Yun-Xuan Weng, Ying Wang, Xiu-Li Wang, Yu-Zhong Wang
Polymer Testing 2010 Volume 29(Issue 5) pp:579-587
Publication Date(Web):August 2010
DOI:10.1016/j.polymertesting.2010.04.002
Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), synthesized via microorganisms, has been paid great attention. However, its biodegradation behavior in pilot-scale composting conditions has not been investigated. In this paper, the biodegradability of PHBV containing 3 mol% of hydroxyvalerate (HV) was tested under composting conditions on both a pilot and a laboratory scale. In the pilot-scale composting conditions, parameters such as pH value, temperature and the amounts of oxygen and CO2 produced were determined periodically. In the laboratory-scale controlled composting, the evolved CO2 was measured so as to calculate the degree of biodegradation of PHBV. It was found that the biodegradation behavior of PHBV in the pilot-scale composting conditions was similar with that in the laboratory-scale. The PHBV film was completely disintegrated in the pilot-scale composting test, and the degree of biodegradation was 81% in the laboratory-scale control composting test. The variations of molecular weight and morphology of PHBV films during composting were also monitored.
Co-reporter:Jian-Bing Zeng, Qun-Ying Zhu, Yi-Dong Li, Zhi-Cheng Qiu, and Yu-Zhong Wang
The Journal of Physical Chemistry B 2010 Volume 114(Issue 46) pp:14827-14833
Publication Date(Web):October 29, 2010
DOI:10.1021/jp104709z
Miscibility and crystallization behaviors of poly(ethylene succinate)/poly(p-dioxanone) (PES/PPDO) blends were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). PES/PPDO blends are completely miscible as proved by the single grass transition temperature (Tg) dependence of composition and decreasing crystallization temperature of the blends in comparison with the respective component. POM observation suggests that simultaneous crystallization of PES and PPDO components in the blends took place, spherulites of one component can crystallize inside the spherulites of the other component, and the unique interpenetrated crystalline morphology has been formed for the blends in the full composition range. Isothermal crystallization kinetics of the blends was studied by DSC and the data were analyzed by the Avrami equation. The results suggest that the crystallization mechanisms of the blends were unchanged but the overall crystallization rates were slowed down compared with neat PES and neat PPDO. WAXD results indicate that the crystal structures of PES and PPDO did not change in the blends.
Co-reporter:Gang Wu;Si-Chong Chen;Qi Zhan
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 21) pp:4811-4822
Publication Date(Web):
DOI:10.1002/pola.24272
Abstract
A series of amphiphilic biodegradable and biocompatible poly(p-dioxanone)-grafted poly(vinyl alcohol) (PVA) copolymers with well-defined structure were obtained by a three-step synthesis based on the “grafting from” concept. The first step (protection step), called the partial silylation of PVA hydroxyl groups, was accomplished by 1,1,1,3,3,3-hexamethyldisilazane and catalyst chlorotrimethylsilane in dimethyl sulfoxide using THF as cosolvent. The second step was the ring-opening polymerization of p-dioxanone (PDO) initiated from the remaining OH groups of the partially silylated PVA. Finally, a deprotection step was followed: the silylether group was deprotected easily under very mild conditions. The synthetic conditions of the first two steps were investigated, and the structures of polymers formed in each step were characterized by various analytical methods. The results showed that the molecular structure of the PVA-g-PPDO could be controlled easily by the degree of silylation and the feed ratio. In addition, the micellization of amphiphilic PVA-g-PPDO copolymers in water was proved by fluorescence spectra and dynamic light scattering, and the relationship between structural parameters of copolymers and micellar properties was studied preliminarily. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Co-reporter:Jian-Bing Zeng;Madhusudhan Srinivansan;Yi-Dong Li;Ramani Narayan
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 24) pp:5885-5890
Publication Date(Web):
DOI:10.1002/pola.24399
Abstract
Ring-opening polymerization of 1,4-dioxan-2-one in bulk was initiated by three titanium alkoxides, titanium dichlorodiisopropoxide (TiCl2(OiPr)2), titanium chlorotriisopropoxide (TiCl(OiPr)3), and titanium tetraisopropoxide (Ti(OiPr)4). The results indicate that the polymerization rate increased with number of OiPr groups in the initiator. High conversion of monomer (90%) and high molecular weight (11.9 × 104 g/mol) of resulting polymer can be achieved in only 5 min at 60 °C with Ti(OiPr)4 as an initiator. Analysis on nuclear magnetic resonance (NMR) spectra suggests the initiating sites for TiCl2(OiPr)2, TiCl(OiPr)3, and Ti(OiPr)4 to be 1.9, 2.6, and 3.8, respectively. Coordination-insertion mechanism for the polymerization via cleavage of the acyl–oxygen bonds of the monomer was proved by NMR investigation. Kinetic studies indicate that polymerization initiated by Ti(OiPr)4 followed a first-order kinetics, with an apparent activation energy of 33.7 kJ/mol. It is noteworthy that this value is significantly lower than earlier reported values with other catalysts, namely La(OiPr)3 (50.5 kJ/mol) and Sn(Oct)2 (71.8 kJ/mol), which makes it an attractive catalyst for reactive extrusion polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Co-reporter:Xiang-Cheng Bian;Li Chen;Jun-Sheng Wang
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 5) pp:1182-1189
Publication Date(Web):
DOI:10.1002/pola.23878
Abstract
A series of thermotropic liquid crystalline polyesters containing phosphorus and aromatic ether groups (TLCP-AEs) were synthesized from p-acetoxybenzoic acid (p-ABA), terephthalic acid (TPA), 4,4′-oxybis(benzoic acid) (OBBA), and acetylated 2-(6-oxid-6H-dibenz(c,e) (1,2) oxaphosphorin 6-yl) 1,4-benzenediol (DOPO-AHQ). The chemical structure and the properties of TLCP-AEs were characterized by Fourier-transform spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), thermogravimetry analysis (TGA), scanning electronic microscopy (SEM), polarizing optical microscopy (POM), limiting oxygen index, and UL-94 tests, respectively. The results showed that TLCP-AEs had low and broad mesophase temperatures (230–400 °C). TLCP-AEs also showed excellent thermal stability; their 5%-weight-loss temperatures were above 440 °C and the char yields at 700 °C were higher than 45 wt %. All TLCP-AE polyesters exhibited high flame retardancy with a LOI value of higher than 70 and UL-94 V-0 rating. The SEM observation revealed that TLCP-AEs had good fibrillation ability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1182–1189, 2010
Co-reporter:Jing Ding, Si-Chong Chen, Xiu-Li Wang and Yu-Zhong Wang
Industrial & Engineering Chemistry Research 2009 Volume 48(Issue 2) pp:788
Publication Date(Web):December 15, 2008
DOI:10.1021/ie8013428
Poly(vinyl alcohol)-graft-lactic acid (PVA-g-LA) was synthesized by melt polycondensation of PVA and lactic acid using stannous chloride as a catalyst. The molecular structure of the copolymer was characterized by 1H NMR. The thermal properties of PVA-g-LA were investigated by differential scanning calorimetry and thermogravimetric analysis. The results showed that the PVA-g-LA copolymer exhibited lower glass transition temperature (Tg) and melting temperature (Tm) and higher decomposition temperature (Td) than pure PVA, and a difference of 60−80 °C between Tm and Td could be obtained, suggesting that the introduction of the oligo-poly(lactic acid) grafted chains can give rise to the melting flow processing of PVA. PVA-g-LA films prepared by compression molding at 140−150 °C had good flexibility and elasticity as well as water resistance. The copolymers have a potential application in food packaging.
Co-reporter:Xin-Ke Jing;Xin-Guo Ge;Xing Xiang;Chuan Wang;Zhe Sun;Li Chen
Polymer International 2009 Volume 58( Issue 10) pp:1202-1208
Publication Date(Web):
DOI:10.1002/pi.2655
Abstract
BACKGROUND: The increasing uses of non-woven fabrics need the development of a kind of novel flame-retardant polyester with low melting temperature. Neopentyl glycol (NPG) and 3-(hydroxyphenylphosphinyl)propionic acid (HPPPA) were used as the third and fourth comonomer to synthesize phosphorus-containing poly[(ethylene terephthalate)-co-(neopentyl terephthalate)] (PENT) with both flame retardancy and low melting temperature.
RESULTS: The chemical structure of PENT was confirmed using Fourier transform infrared, 1H NMR, 13C NMR and 31P NMR spectroscopy. PENT displays a monomodal gel permeation chromatography curve. When the content of NPG was kept at 10 wt% and the content of HPPPA increased to 5 wt%, the melting temperature (Tm) of the resulting PENT5/10 decreases to 171.2 °C, a 34.6 °C decrease compared to that of PENT0/10 (containing no HPPPA). The flammability of the PENTs was characterized with the limiting oxygen index (LOI) test, the UL-94 vertical test and the cone calorimeter test. The incorporation of HPPPA can significantly improve the flame retardancy of the PENTs, the LOI values of the PENTs increasing from 24.4 to 37.6, as the loading of HPPPA increases from 0 to 5 wt%.
CONCLUSION: The PENTs possess both low melting temperatures and excellent flame retardancy. HPPPA can be used as fourth comonomer to improve the flame retardancy of the PENTs, while decreasing the Tm value of the copolyester. Copyright © 2009 Society of Chemical Industry
Co-reporter:Yi Deng, Cheng-Shou Zhao, Yu-Zhong Wang
Polymer Degradation and Stability 2008 Volume 93(Issue 11) pp:2066-2070
Publication Date(Web):November 2008
DOI:10.1016/j.polymdegradstab.2008.02.022
In order to compare their inherent flame retardancy and thermal stability, two phosphorus-containing thermotropic liquid crystalline copolyesters (P-TLCP) were synthesized by melting transesterification. Additionally based on the facts that the P-TLCP can work as a functional additive to enhance the flame retardancy and mechanical property of PET, we further studied the flame retardant mechanism. Scanning Electronic Microscope (SEM) observations show that the char from PET/P-TLCP is more compact, therefore more efficiently resists fire and heat attack than pure PET. Moreover, Fourier Transform Infrared Spectroscopy (FTIR) measurements of evolved gas, indicate that P-TLCP decomposes to produce phosphorus-containing small molecular compounds during the pyrolysis process, such that P-TLCP could play a flame retardant role in vapour phase. Furthermore, P-TLCP strongly inhibits the generation of combustible compounds in the pyrolysis of PET, which also helps to resist fire propagation.
Co-reporter:Gui-Cheng Liu, Wen-Qiang Zhang, Xiu-Li Wang, Yu-Zhong Wang
Chinese Chemical Letters (February 2017) Volume 28(Issue 2) pp:354-357
Publication Date(Web):February 2017
DOI:10.1016/j.cclet.2016.10.014
Co-reporter:Zhi-Jie Cao, Xue Dong, Teng Fu, Shi-Bi Deng, Wang Liao, Yu-Zhong Wang
Polymer Degradation and Stability (February 2017) Volume 136() pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.polymdegradstab.2016.12.004
Red phosphorus (RP) and the coated RP with melamine formaldehyde resin (MFcP) were foamed with isocyanates to prepare polyurethane foam (PUF). The cell size of PUF/RP became uneven and more spherical, and the cell struts became thicker. The cells of PUF/MFcP were much more uniform in size and more spherical in shape. Addition of flame retardants increased the densities, compressive strength and thermal conductivity of the foams, but decreased the blind hole percents. Thermal gravimetric analysis (TGA) tests exhibited that decomposition of both PUF/RP and PUF/MFcP took place at lower temperatures than that of neat PUF. However, the maximum decomposition temperature (Tmax) for PUF was increased from 300 °C to ca. 340 °C when RP or MFcP was added. Load of RP or MFcP with 80 pphp or higher increased the limiting oxygen index (LOI) of PUF to higher than 25% and pass UL-94 V-0 grade. In the cone calorimetry tests (CC), It indicated that PUF/MFcP100 released much less heat and smoke than PUF/RP100 and PUF. The smoke release of PUF/MFcP100 was reduced by almost 75% than that of PUF/RP100. The toxic gas release of PUF/MFcP100 was reduced more than 50% than that of PUF/RP100. The smoke emission of PUF increased significantly after addition of RP comparing with that addition of MFcP greatly relief the situation. The corresponding mechanism was proposed.
Co-reporter:Cong Deng, Huajie Yin, Rui-Min Li, Sheng-Chao Huang, Bernhard Schartel, Yu-Zhong Wang
Polymer Degradation and Stability (April 2017) Volume 138() pp:142-150
Publication Date(Web):April 2017
DOI:10.1016/j.polymdegradstab.2017.03.006
Co-reporter:Juan Wang, Dan Zhao, Ke Shang, Yu-Tao Wang, Dan-Dan Ye, A.-Hui Kang, Wang Liao and Yu-Zhong Wang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 24) pp:NaN9389-9389
Publication Date(Web):2016/05/23
DOI:10.1039/C6TA03146C
We demonstrated the preparation of a novel aerogel simply by cross-linking a gelatin physical gel with formaldehyde (cGel) and using a subsequent freeze-drying procedure. A hydrophobic absorbent material (MTCS-cGel aerogel) was further obtained by thermal chemical vapor deposition (CVD) of methyltrichlorosilane (MTCS). Rheological tests were carried out to investigate the cross-linking between gelatin and formaldehyde. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and wettability of oil and water results proved that successful silanization occurred on/in the aerogels. These results also indicated that the MTCS-cGels had low densities (5–8 kg m−3), high porosities (>95%) with uniform pore sizes, and unique laminar/fibrous 3D networks. The oleophilic aerogels possessed high oil absorption capacities of 70–123 times that of their dry weights. Furthermore, the absorbents exhibited excellent elasticity and ultrasoftness with a stress of only 2.0 kPa at 60% strain. This property endowed the aerogels with super-recyclability where 83–85% of their full absorption capacity was maintained after 5000 times of compression. The high oil absorption performance, super-recyclability, sustainability, biodegradability and cost-efficiency make this novel absorbent a promising candidate for large-scale oceanic oil contaminant removal.
Co-reporter:Xin-Ke Jing, Xiao-Shi Wang, De-Ming Guo, Yao Zhang, Fei-Yu Zhai, Xiu-Li Wang, Li Chen and Yu-Zhong Wang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 32) pp:NaN9272-9272
Publication Date(Web):2013/05/23
DOI:10.1039/C3TA11267E
This manuscript reports a new method to solve the conflict between the flame retardance and anti-dripping of poly(ethylene terephthalate) by introducing azobenzene groups into the main-chain. This novel polyester containing azobenzene units in the main chain (PEAT) was synthesized via esterification and copolycondensation of terephthalic acid, ethylene glycol and azobenzene-4,4′-dicarboxylic acid. TG-DSC, rheological and UV-Vis results proved the occurrence of the thermal and chemical crosslinking reaction by adjacent azobenzene groups. In the TG test, the residue and thermooxidative stability were obviously increased by the high-temperature crosslinking of the azobenzene groups. The cone calorimetric analysis and LOI tests further confirmed the self-extinguishing properties and inhibition of melt-dripping. Elemental analysis results indicated that besides partial decomposition of azobenzene groups into N2, most nitrogen was retained in the residue after high-temperature crosslinking. Besides, the char became more compact with an increase of azobenzene-4,4′-dicarboxylic acid. All the results demonstrated that through the high-temperature crosslinking of the azobenzene group, PEAT exhibited a good balance between flame retardance and anti-dripping properties.
Co-reporter:Lan Bai, Xiao-hui Wang, Fei Song, Xiu-li Wang and Yu-zhong Wang
Chemical Communications 2015 - vol. 51(Issue 1) pp:NaN96-96
Publication Date(Web):2014/11/03
DOI:10.1039/C4CC07012G
A dual-responsive drug delivery system simulating an AND logic gate is developed by core-cross-linking of a disulfide-containing anticancer prodrug with Cu2+ for safe and efficient delivery of anticancer drugs. These prodrug nanoparticles are stable and exhibit nearly no premature drug release, and allow a fast drug release under simulated intracellular conditions, realizing a precise drug delivery towards cell nuclei.
Co-reporter:Si-Chong Chen, Gang Wu, Jing Shi and Yu-Zhong Wang
Chemical Communications 2011 - vol. 47(Issue 14) pp:NaN4200-4200
Publication Date(Web):2011/03/02
DOI:10.1039/C1CC00050K
Nano aggregates in aqueous medium with a novel “star anise”-like morphology were prepared from a branched alternating multi-block copolymer composed of 3-arm star-like hydrophobic poly(p-dioxanone) block and linear hydrophilic poly(ethylene glycol) block. The influence of block length on the morphology of the nano aggregate was investigated.
Co-reporter:Man-Jie He, Wen-Xia Xiao, Hui Xie, Cheng-Jie Fan, Lan Du, Xiao-Ying Deng, Ke-Ke Yang and Yu-Zhong Wang
Inorganic Chemistry Frontiers 2017 - vol. 1(Issue 2) pp:NaN353-353
Publication Date(Web):2016/08/15
DOI:10.1039/C6QM00047A
How to realize the multi-stimuli-response of shape-memory polymers in a simple system is a big challenge for researchers. In this study, a facile approach to produce a series of ternary nanocomposites made of a poly(butylene succinate)–poly(ε-caprolactone) (PBSPCL) multiblock copolymer matrix and multi-walled carbon nanotubes (MWCNTs) is described. MWCNTs were easily introduced into the double-crystalline copolymer matrix using solution mixing and solvent casting processes, successively. As a consequence of the immiscibility between these two polymeric segments, the spontaneous selective dispersion of MWCNTs is realized in the matrix with refined microphase separation morphology. The different affinity of MWCNTs for the PBS or PCL segment drove the MWCNTs to be localized in the PBS domain preferentially, as demonstrated by TEM analysis. This elaborate design leads to a significant reduction of percolation thresholds with the optimized composition of the nanocomposites. Moreover, the selective dispersion of MWCNTs in the hard PBS segment improved the strength of the material without deteriorating its ductility. Dynamic thermomechanical tests revealed that the PBSPCL copolymers exhibit an excellent dual-shape memory effect, as attested by the fix ratio (Rf) and recovery ratio (Rr) of 98%. After incorporation of MWCNTs into the matrix, the electro- and NIR-induced shape-memory effects have been realized, and the sample containing 40% PBS segment and 1 wt% MWCNTs exhibits optimal structure and performance.
Co-reporter:Hai-Yi Zhong, Li Chen, Rong Yang, Zhi-Ying Meng, Xiao-Min Ding, Xiao-Feng Liu and Yu-Zhong Wang
Journal of Materials Chemistry A 2017 - vol. 5(Issue 13) pp:NaN3314-3314
Publication Date(Web):2017/03/15
DOI:10.1039/C6TC05493E
An azobenzene-containing thermotropic liquid crystalline polyester showing unique thermo- and photo-responsive behaviours was synthesized by polycondensation from mesogenic dial 4,4′-bis(6-hydroxyhexyloxy)azobenzene (BHHAB) with 2-phenylsuccinic acid (PSA), and named as poly(4,4′-bis(6-hydroxyhexyloxy)azobenzene phenylsuccinate) (PBHPS). Liquid crystalline behaviours were investigated through differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and wide-angle X-ray diffraction (WAXD). PBHPS showed a smectic phase with strong π–π interactions between the adjacent phenyl rings or between the side group and mesogenic unit, which could be regarded as physical crosslinking points that made PBHPS have good shape memory and self-healing properties. A series of PBHPS/methylcellulose bilayer films were prepared to study the reversible photo-mechanical properties. UV-vis absorption spectra were used to study the reversible photo-responsive behaviour of the polyester, proving that the reversible photoisomerization-induced volume expansion of the PBHPS layer resulted in good reversible photo-responsive properties.
Co-reporter:Zhu-Bao Shao, Cong Deng, Yi Tan, Li Yu, Ming-Jun Chen, Li Chen and Yu-Zhong Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 34) pp:NaN13965-13965
Publication Date(Web):2014/07/01
DOI:10.1039/C4TA02778G
Ammonium polyphosphate (APP) is not an efficient flame retardant for polypropylene (PP) when it is used alone. In order to improve its flame-retardant efficiency, ethanolamine (ETA) was used to chemically modify APP via ion exchange reaction. The resulting ethanolamine-modified ammonium polyphosphate (ETA-APP) was alone applied to flame retard PP, the limiting oxygen index (LOI) value could reach 35.0% and the vertical burning test (UL-94) could pass the V-0 rating at a loading of 35 wt% ETA-APP. Moreover, cone calorimeter (CC) test results showed that the heat release rate (HRR), the total heat release (THR), the mass loss rate (MLR), the smoke production rate (SPR) and the total smoke production (TSP) of PP/35 wt% ETA-APP composite largely decreased, for example, by 77.2%, 88.5% and 77.9% for THR, TSP and the fire growth rate (FGR), respectively, compared with PP containing an equal amount of APP. In addition, the residual char of PP/35 wt% ETA-APP increased by 195.6% compared with that of PP/35 wt% APP. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the flame retardant mechanism of ETA-APP. It was confirmed that the formation of P–O–C and P–N–C structures, resulting from the incorporation of ETA could greatly improve the stability of intumescent char layer and consequently lead to the much better flame retardancy of ETA-APP than that of unmodified APP. Experimental results demonstrated that the prepared ETA-APP acted not only as the acid source and blowing source as efficient as unmodified APP, but also as an excellent charring agent beyond the unmodified APP.
Co-reporter:Rong Yang, Li Chen, Chao Ruan, Hai-Yi Zhong and Yu-Zhong Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 30) pp:NaN6164-6164
Publication Date(Web):2014/05/28
DOI:10.1039/C4TC00512K
A series of main-chain thermotropic liquid crystalline polyesters were synthesized by polycondensation from mesogenic dial such as 4,4′-bis(6-hydroxyhexyloxy)biphenyl (BHHBP) and various diacids with different substituents such as succinic acid (no side group), 2-methylsuccinic acid (aliphatic side group) and 2-phenylsuccinic acid (aromatic side group), named poly(4,4′-bis(6-hydroxyhexyloxy)biphenyl succinate) (PBDS), poly(4,4′-bis(6-hydroxyhexyloxy)biphenyl methylsuccinate) (PBDMS), and poly(4,4′-bis(6-hydroxyhexyloxy)biphenyl phenylsuccinate) (PBDPS), respectively. Liquid crystalline behaviours were investigated through differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and small angle X-ray scattering (SAXS) and the thermal stability of the polyesters was determined via thermogravimetric analysis (TGA). PBDS, PBDMS and PBDPS showed a SmF, SmB and SmA phase, respectively. On enlarging the side group, the d-spacing of the smectic layer increased, indicating folding packing of the polymer chains. Therefore, the adjacent phenyl rings in side groups stacked well together and formed strong π–π interactions even when the temperature was higher than Ti. The special structure of PBDPS could provide good mechanical properties. Thus, PBDPS exhibited the maximum tensile stress (28.6 MPa) and the highest elongation at break (1060%). Furthermore, the strong π–π interaction can act as netpoints; therefore, PBDPS exhibited excellent shape fixing (>99%) and shape recovery ratio (>99%) with large strain (>220%).
Co-reporter:Hai-Bo Zhao, Li Chen, Jun-Chi Yang, Xin-Guo Ge and Yu-Zhong Wang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 37) pp:NaN19857-19857
Publication Date(Web):2012/08/08
DOI:10.1039/C2JM34376B
In this manuscript, contradiction between the non-flammability and non-dripping of polyesters could be solved by copolymerizing terephthalic acid and ethylene glycol together with a pendent phenylethynyl-based monomer named 4-(phenylethynyl) di(ethylene glycol) phthalate (PEPE), which exhibited a cross-linkable nature at a proper temperature. TG-DSC simultaneous thermal analysis, FTIR, dissolution tests and rheological investigations proved the thermal cross-linking behavior of the copolyester, which was not active at the temperature of polymerization and processing but could cross-link rapidly at higher temperature before burning. LOI tests, cone calorimetry and small-scale flame tests further confirmed the self-extinguishment and inhibition for melt-dripping could be achieved through the cross-linking during burning, despite the absence of any flame-retardant element (say, bromine, chlorine, phosphorus, or nitrogen, etc.). Rheological analyses and the SEM microphotographs of the char showed P(ET-co-P)s exhibited a greater complex viscosity through the cross-linking at high temperature, leading to compact char residue, flame-retardant and anti-dripping effects.
Co-reporter:Hong-Bing Chen, Li Chen, Yi Zhang, Jing-Jing Zhang and Yu-Zhong Wang
Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 23) pp:NaN11075-11075
Publication Date(Web):2011/05/12
DOI:10.1039/C0CP02176H
A novel phosphorus-containing copolyester (PTTP), poly(trimethylene terephthalate) (PTT) copolyester with a bulky linking pendent group of 9,10-dihydro-10-[2,3-di(hydroxycarbonyl) propyl]-10-phosphaphenanthrene-10-oxide (DDP) was prepared, and its crystallization, crystal morphology and interference color were investigated in this article for the first time. Differential scanning calorimeter (DSC) results showed that with the increase of DDP content, the melting point (Tm) and crystallization ability of PTTP decreased. WAXD results suggests that the three samples share one crystal structure, however the crystallinity decreases with increasing DDP content. Polarized optical microscope (POM) observation indicated that the samples showed non-banded spherulites at a lower and higher temperature, and banded spherulites at the middle temperature range. From the micrographs obtained from scanning electronic microscopy (SEM) and atomic force microscopy (AFM), ringed patterns with many defects could be found for samples with higher DDP contents, which crystallized at a lower temperature, and a transformation from square-shaped spherulites to circular spherulites was noted for samples with higher DDP contents, which crystallized at a higher temperature. The interference color of the spherulites was also studied and it was shown that with the increase of film thickness or decrease of DDP content, the spherulites became more colorful under POM observation, indicating that the hindering effect and randomness caused by incorporating the DDP monomer with a bulky pendent group into the PTT molecular chain exhibited a negative influence on the molecular mobility and crystallization ability of the copolyester, and led to the formation of the defective band morphology and the less colorful interference color of the PTTP spherulites.
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![1-Butanesulfonic acid, (1-oxido-2,6,7-trioxa-1-phosphabicyclo[2.2.2]oct-4-yl)methyl ester](/data/chemimg/3783900/1962978-13-7.png)
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![1H-Pyrrole-1-propanoic acid, 2,5-dihydro-2,5-dioxo-, 2-[1-[(2S,4S)-4-[(3-amino-2,3,6-trideoxy-α-L-lyxo-hexopyranosyl)oxy]-1,2,3,4,6,11-hexahydro-2,5,12-trihydroxy-7-methoxy-6,11-dioxo-2-naphthacenyl]-2-hydroxyethylidene]hydrazide](/data/chemimg/105600/766503-90-6_b.png)
![Propanoic acid, 2,2'-[carbonothioylbis(thio)]bis[2-methyl-](/data/chemimg/104200/355120-40-0.png)
![Propanoic acid, 2,2'-[carbonothioylbis(thio)]bis[2-methyl-](/data/chemimg/104200/355120-40-0_b.png)
![Ethanol, 2-[4-(phenylazo)phenoxy]-](http://img.cochemist.com/ccimg/92300/92245-57-3.png)
![Ethanol, 2-[4-(phenylazo)phenoxy]-](http://img.cochemist.com/ccimg/92300/92245-57-3_b.png)
![PHENOL, 4,4'-[1,4-PHENYLENEBIS(OXY)]BIS-, DIACETATE](http://img.cochemist.com/ccimg/83800/83743-89-9.png)
![PHENOL, 4,4'-[1,4-PHENYLENEBIS(OXY)]BIS-, DIACETATE](http://img.cochemist.com/ccimg/83800/83743-89-9_b.png)
![POLY[1,4-PIPERAZINEDIYL(1,2-DIOXO-1,2-ETHANEDIYL)]](http://img.cochemist.com/ccimg/66600/66536-66-1.png)
![POLY[1,4-PIPERAZINEDIYL(1,2-DIOXO-1,2-ETHANEDIYL)]](http://img.cochemist.com/ccimg/66600/66536-66-1_b.png)
![Butanedioic acid, 2-[(6-oxido-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)methyl]-](/data/chemimg/1506600/63562-33-4.png)
![Butanedioic acid, 2-[(6-oxido-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)methyl]-](/data/chemimg/1506600/63562-33-4_b.png)
![2,2,2-TRIFLUORO-N-(2-OXA-6-AZASPIRO[3.4]OCT-8-YL)ACETAMIDE](http://img.cochemist.com/ccimg/39900/39887-40-6.png)
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![Poly[oxy(methyl-1,2-ethanediyl)oxy(1,10-dioxo-1,10-decanediyl)]](http://img.cochemist.com/ccimg/28800/28776-64-9.png)
![Poly[oxy(methyl-1,2-ethanediyl)oxy(1,10-dioxo-1,10-decanediyl)]](http://img.cochemist.com/ccimg/28800/28776-64-9_b.png)
![Poly[1,4-piperazinediyl(1,4-dioxo-1,4-butanediyl)]](http://img.cochemist.com/ccimg/27000/26967-91-9.png)
![Poly[1,4-piperazinediyl(1,4-dioxo-1,4-butanediyl)]](http://img.cochemist.com/ccimg/27000/26967-91-9_b.png)
![Poly[oxy-1,2-ethanediyloxy(1,4-dioxo-1,4-butanediyl)]](http://img.cochemist.com/ccimg/25700/25667-11-2.png)
![Poly[oxy-1,2-ethanediyloxy(1,4-dioxo-1,4-butanediyl)]](http://img.cochemist.com/ccimg/25700/25667-11-2_b.png)
![Poly[oxy-1,4-butanediyloxy(1,6-dioxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25000/24936-97-8.png)
![Poly[oxy-1,4-butanediyloxy(1,6-dioxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25000/24936-97-8_b.png)
![1-[4-[4-(4-ACETYLPHENOXY)PHENOXY]PHENYL]ETHANONE](http://img.cochemist.com/ccimg/24400/24319-76-4.png)
![1-[4-[4-(4-ACETYLPHENOXY)PHENOXY]PHENYL]ETHANONE](http://img.cochemist.com/ccimg/24400/24319-76-4_b.png)
![[1,1'-Biphenyl]-3,3'-diamine, 4,4'-dimethyl-](http://img.cochemist.com/ccimg/23900/23806-81-7.png)
![[1,1'-Biphenyl]-3,3'-diamine, 4,4'-dimethyl-](http://img.cochemist.com/ccimg/23900/23806-81-7_b.png)
![Phenol, 4,4'-[1,4-phenylenebis(oxy)]bis-](http://img.cochemist.com/ccimg/15100/15051-26-0.png)
![Phenol, 4,4'-[1,4-phenylenebis(oxy)]bis-](http://img.cochemist.com/ccimg/15100/15051-26-0_b.png)
![5,12[1',2']:6,11[1'',2'']-Dibenzenodibenzo[a,e]cyclooctene, 5,6,11,12-tetrahydro-](/data/chemimg/924600/1627-06-1.png)
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![4-[(1E)-prop-1-en-1-yl]phenol](http://img.cochemist.com/ccimg/600/539-12-8.png)
![4-[(1E)-prop-1-en-1-yl]phenol](http://img.cochemist.com/ccimg/600/539-12-8_b.png)
![Poly[oxy-1,2-ethanediyloxy-1,2-ethanediyloxy(1,4-dioxo-1,4-butanediyl)]](http://img.cochemist.com/ccimg/26800/26793-77-1.png)
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![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4.png)
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4_b.png)
![5H-Benzo[a]phenoxazin-5-one,9-(diethylamino)-](http://img.cochemist.com/ccimg/7400/7385-67-3.png)
![5H-Benzo[a]phenoxazin-5-one,9-(diethylamino)-](http://img.cochemist.com/ccimg/7400/7385-67-3_b.png)
![2-[anthracen-9-ylmethyl(2-hydroxyethyl)amino]ethanol](http://img.cochemist.com/ccimg/109300/109297-66-7.png)
![2-[anthracen-9-ylmethyl(2-hydroxyethyl)amino]ethanol](http://img.cochemist.com/ccimg/109300/109297-66-7_b.png)
![1-Hexanol, 6,6'-[[1,1'-biphenyl]-4,4'-diylbis(oxy)]bis-](http://img.cochemist.com/ccimg/97100/97087-90-6.png)
![1-Hexanol, 6,6'-[[1,1'-biphenyl]-4,4'-diylbis(oxy)]bis-](http://img.cochemist.com/ccimg/97100/97087-90-6_b.png)
![Poly[oxy(1-oxo-1,2-ethanediyl)oxy-1,2-ethanediyl]](http://img.cochemist.com/ccimg/31700/31621-87-1.png)
![Poly[oxy(1-oxo-1,2-ethanediyl)oxy-1,2-ethanediyl]](http://img.cochemist.com/ccimg/31700/31621-87-1_b.png)
![Poly[oxy(1,4-dioxo-1,4-butanediyl)oxy-1,4-butanediyl]](http://img.cochemist.com/ccimg/26300/26247-20-1.png)
![Poly[oxy(1,4-dioxo-1,4-butanediyl)oxy-1,4-butanediyl]](http://img.cochemist.com/ccimg/26300/26247-20-1_b.png)
![Poly[oxy[(1S)-1-methyl-2-oxo-1,2-ethanediyl]]](http://img.cochemist.com/ccimg/26200/26161-42-2.png)
![Poly[oxy[(1S)-1-methyl-2-oxo-1,2-ethanediyl]]](http://img.cochemist.com/ccimg/26200/26161-42-2_b.png)