Co-reporter:Yan Zhang;Xiaonan Li;Zhenhu Cao;Anna A. Stec;T. Richard Hull
Industrial & Engineering Chemistry Research April 8, 2015 Volume 54(Issue 13) pp:3247-3256
Publication Date(Web):2017-2-22
DOI:10.1021/ie504200y
A novel oligomeric intumescent fire-retardant chelate, zinc phosphonated poly(ethylene imine) (Zn-PEIP), with a variable Zn2+ loading, was synthesized. The chemical structure of Zn-PEIP was confirmed by FTIR, 13C NMR, and 31P NMR spectroscopies. The thermal behavior and fire retardancy of low-density polyethylene (LDPE) containing 25 wt % Zn-PEIPs with different amounts of Zn2+ were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI) measurements, and cone calorimetry. The TGA results showed that higher concentrations of Zn2+ improved the thermal stability and increased the residue yield of LDPE. However, the data from the LOI and cone calorimetry tests showed that there is an optimum concentration of Zn2+ for the best fire-retardancy performance of LDPE. This behavior is ascribed to the high cross-link density resulting from zinc bridges, preventing normal swelling of the intumescent system. The surface morphology of the char was characterized by digital photography and scanning electron microscopy (SEM). This confirmed the optimum intumescence and coherent and strong barrier layer formation at an intermediate Zn2+ loading.
Co-reporter:Zhenghong Guo;Shiya Ran
Journal of Thermal Analysis and Calorimetry 2017 Volume 128( Issue 3) pp:1719-1730
Publication Date(Web):23 January 2017
DOI:10.1007/s10973-017-6093-y
Graphene nanoplatelets (GNPs) were introduced into polystyrene (PS)/brominated polystyrene (BPS) blends to suppress the large amounts of smoke generated from brominated flame retardants during combustion. A Lewis acid catalyst (AlCl3) was added to initiate Friedel–Crafts reaction to produce macrocarbocations interacted with graphene sheets by electrostatic attraction, leading to an improved dispersive state of GNPs in polymer matrix. And the scanning electron microscopy (SEM) showed that more compact and integrated char barriers were formed in PS/BPS/GNPs/AlCl3 composite. Cone calorimeter tests revealed that the continuous and uniform char barriers of GNPs fabricated by Friedel–Crafts reaction prevented the spread of combustion, reduced the heat release in the initial stage of combustion, and especially suppressed the smoke release effectively. The mutual influences among the char barrier effect of GNPs, the electrostatic attraction between macrocarbocations and graphene sheets, the catalytic degradation of Lewis acid catalyst, the solid lubricant effect and the heat gathering effect of GNPs caused the complex microstructure changes, which lead to the complex rheological behaviors of PS/BPS/GNPs/AlCl3 composite. The pyrolysis products showed that the light carbon decreased and the heavy carbon increased in PS/BPS/GNPs/AlCl3 composite, revealing that the char barrier of GNPs fabricated by Friedel–Crafts reaction played an effective protective layer to prevent polymer form erosion of high temperature.
Co-reporter:
Journal of Applied Polymer Science 2017 Volume 134(Issue 9) pp:
Publication Date(Web):2017/03/05
DOI:10.1002/app.44551
ABSTRACTThe influence of fullerene (C60) on the flame retardancy and thermal stability of high-density polyethylene (HDPE)/aluminum hydroxide (ATH) composites was studied. After the addition of three portions of C60 to an HDPE–ATH (mass ratio = 100:120) composite, a V-0 rating in the UL-94 vertical combustion test was achieved, and the limiting oxygen index increased by about 2%. The results of cone testing also showed that the addition of C60 effectively extended the time to ignition and the time to maximum heat-release rate while cutting down the peak heat-release rate. Thus, fewer flame retardants were needed to achieve a satisfactory flame retardance. Consequently, the adverse effects on the mechanical properties because of the high level of flame-retardant loading was reduced, as evidenced by the obvious enhancements in the tensile strength, elongation at break, and flexural strength. Electron spin resonance spectroscopy proved that C60 was an efficient free-radical scavenger toward HO· radicals. Thermogravimetric analysis coupled to Fourier transform infrared spectroscopy demonstrated that in both N2 and air atmospheres, C60 increased the onset temperature of the matrix by about 10 °C because of its enormous capacity to absorb free radicals evolved from the degradation of the matrix to form crosslinked network, which was covered by aluminum oxide. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44551.
Co-reporter:Jian Jing, Yan Zhang, Xinlei Tang, Yang Zhou, Xiaonan Li, Baljinder K. Kandola, Zhengping Fang
Polymer 2017 Volume 108() pp:361-371
Publication Date(Web):13 January 2017
DOI:10.1016/j.polymer.2016.12.008
•A novel bio-based polyelectrolyte was synthesized using plant-derived resource diphenolic acid.•A novel hybrid with core/shell structure was fabricated via layer-by-layer assembly method.•The core/shell hybrid imparted both highly efficient flame retardancy and toughness to polylactic acid.In this study, a facile approach to fabricate a novel bio-based hybrid (BBH) with core/shell structure is presented by taking advantage of plant-derived resources. The BBH developed herein comprises of an inorganic core of ammonium polyphosphate (APP), covered with an organic shell that is constructed via layer-by-layer assembly of a novel bio-based polyelectrolyte (BPE) and polyethylenimine (PEI). BBH can simultaneously enhance the flame retardancy and toughness of polylactic acid (PLA) with very high efficiency. The flame retardant PLA composite can pass UL94 V0 rating at the BBH loading content of 10 wt%. The efficient flame retardant performance is due to its effectiveness in both gas and condensed phases. More importantly, the flame retardant PLA composite containing 10 wt% BBH exhibits ductile fracture with an elongation at break of 27.3%, which is much higher than that of neat PLA (8%). The debonding and plastic void deformation of the PLA matrix around the BBH are responsible for the enhanced toughness. This work provides important hints for devising highly efficient multifunctional flame retardant and broadening the application field of renewable resources.
Co-reporter:Jian Jing, Yan Zhang, Zhengping Fang
Polymer 2017 Volume 108() pp:29-37
Publication Date(Web):13 January 2017
DOI:10.1016/j.polymer.2016.11.036
•A novel bio-based biphosphate was synthesized using plant-derived diphenolic acid.•The biphosphate endowed efficient flame retardancy to PLA through gas phase action.•Depression on the mechanical properties of flame retardant PLA was minimal.In an effort to impart fire protection properties to polylactic acid (PLA) utilizing renewable resources, diphenolic acid, a plant derived compound, was used to synthesize a biphosphate (hereinafter shortened as FR) that contains two types of phosphorus. The chemical structure of FR was confirmed by 1H NMR and 31P NMR. UL-94 V0 rating and LOI value of 27.4 for PLA were achieved at the FR loading content of 16 wt%. Besides, the heat release rate and total heat release of the flame retardant PLA were decreased remarkably in cone calorimetric tests. The significantly increased CO/CO2 ratio in cone tests and the presence of phosphorous containing compound in gas phase in TG-FTIR tests confirmed that the gas phase mechanism is mainly responsible for the improved flame retardant performance. Differential scanning calorimetric analysis showed the glass transition temperature of PLA composites have no change indicating no plasticizing effect of the FR. Finally, the tensile tests revealed that the ductility of PLA was sustained and tensile strength was depressed in a minimal content after the FR was incorporated. This work suggests a novel green strategy for improving flame retardancy performance of PLA and promoting the utilization of sustainable resource.
Co-reporter:Zhenghong Guo, Runfeng Ye, Liping Zhao, Shiya Ran, Zhengping Fang, Juan Li
Composites Science and Technology 2016 Volume 129() pp:123-129
Publication Date(Web):6 June 2016
DOI:10.1016/j.compscitech.2016.04.024
Fullerene (C60) decorated graphene oxide (GO), denoted as GO-d-C60, was synthesized through a three-step chemical process, including acylating chlorination of GO, amino-functionalization of GO and addition reaction of C60 molecules with amino groups, with the purpose of promoting the dispersion of GO in high density polyethylene (HDPE) and further improving thermal stability and flame retardancy of HDPE/GO composite. Infrared spectroscopy (IR), transmission electron micrographs (TEM) and X-ray photoelectron spectroscopy (XPS) proved that about 2.3 wt.% of C60 molecules, with the size of about 40–70 nm, were bonded onto the surface of GO and mainly located on the edge of GO sheets. The chemical decoration made GO-d-C60 to have better dispersion in HDPE than GO, favoring the formation of compact and integrated char barriers when heated or ignited. Consequently, GO-d-C60 improved the thermal stability and flame retardancy of HDPE more effectively than pristine GO, due to the assembly of the barrier effect of GO and the radical-trapping effect of C60.
Co-reporter:Shan Liu, Zhengping Fang, Hongqiang Yan and Hao Wang
RSC Advances 2016 vol. 6(Issue 7) pp:5288-5295
Publication Date(Web):12 Jan 2016
DOI:10.1039/C5RA25988F
In this paper, the thermal stability and fire retardant behavior of epoxy resin (ER) composites filled with graphene nanosheets (GNS) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were investigated. Addition of GNS and DOPO changed the decomposition pathway of ER. During combustion, DOPO played a key flame retardancy role in the gas phase and the char enhancement in the condensed phase, while GNS played an effect in the condensed phase. Addition of 5 wt% GNS and DOPO separated, the peak heat release rate (PHRR) of ER was reduced from 1194 kW m−2 to 513.9 kW m−2 and 937.1 kW m−2, respectively. With the combined addition of GNS and DOPO, the flame retardancy of ER composites was significantly improved. The PHRR was reduced to 396 kW m−2 at the addition of 2.5% GNS and 2.5% DOPO. The same tendency was obtained for the total heat release (THR), showing a synergistic effect between GNS and DOPO in improving the flame retardancy of ER composites. The combined addition of GNS and DOPO extended the diffusion path for heat and combustible gas while DOPO captured the free radicals which further retarded ER degradation.
Co-reporter:Jian Jing, Yan Zhang, Xinlei Tang and Zhengping Fang
RSC Advances 2016 vol. 6(Issue 54) pp:49019-49027
Publication Date(Web):12 May 2016
DOI:10.1039/C6RA06742E
Organophosphorus compounds as one of the most preferred flame retardants are traditionally derived from petroleum resources. Of recent interest is the exploration of renewable candidates as the precursors to synthesise these compounds. Here, we report the synthesis of a novel bio-based polyphosphonate (BPPT) through the reaction of plant-derived diphenolic acid (DPA), caged bicyclic phosphorus (PEPA) and phenylphosphonic dichloride (PPDC) in two steps. The BPPT was used as a flame retardant to prepare polylactic acid (PLA) blends. Significant enhancement in the limiting oxygen index of PLA (28.8, 33.7 and 35.4 with 2 wt%, 4 wt%, and 6 wt% of BPPT, respectively, in the PLA blends) was obtained. Additionally, the results in the UL94 flammability tests demonstrates that BPPT is effective to quench the flame, which facilitate PLA blends to achieve a V0 level at a BPPT loading of 4 wt%. The data of the cone tests and thermal gravimetric analysis confirm that a gas phase mechanism is mainly responsible for the highly efficient flame retardancy. Moreover, the tensile test results indicate that the BPPT-induced depression of the mechanical properties of the flame retardant blends is minimal. The flame retardant PLA blends developed herein contain a bio-mass content of more than 95 wt%.
Co-reporter:Xinrui Zhou;Shiya Ran;Hefeng Hu
Journal of Thermal Analysis and Calorimetry 2016 Volume 125( Issue 1) pp:199-204
Publication Date(Web):2016 July
DOI:10.1007/s10973-016-5354-5
The effects of fullerene (C60) and aluminum hydroxide (ATH)/C60 combination on the thermal stability, flame retardancy and mechanical properties of styrene–butadiene–styrene block copolymer (SBS) were investigated. Adding small amount (0.5–2 mass%) of C60 into SBS matrix raised the initial decomposition temperature of the composites slightly, while C60 alone had little influence on the flame-retardant behavior. In SBS/ATH/C60 system, however, the addition of C60 significantly improved the UL-94 vertical combustion grade and limiting oxygen index. The total content of the flame retardant in SBS/ATH/C60 system (56 mass%) was lower than that in SBS/ATH system (60 mass%) when UL-94 reached V0 level. Consequently, the adverse effects on the mechanical properties due to the high level of flame-retardant loading reduced. Meanwhile, the data obtained from cone calorimetric test indicated that C60 can not only reduce the heat release rate, but also raise the char residue of SBS/ATH composites.
Co-reporter:Nannan Li, Hongqiang Yan, Lei Xia, Lebo Mao, Zhengping Fang, Yihu Song, Hao Wang
Composites Science and Technology 2015 Volume 121() pp:82-88
Publication Date(Web):16 December 2015
DOI:10.1016/j.compscitech.2015.07.013
Ramie fabrics were firstly treated with amino functional silane coupling agent. Then the layer-by-layer self-assemble technique was used to develop flame retardant coating on flexible and porous ramie fabrics through the electronegativity of ammonium polyphosphate (APP) and the electropositivity of polyethyleneimine (PEI). The content of the coating was measured to be 13.8 wt.%. The flame retardant ramie/polybenzoxazine composites were prepared with APP/PEI treated ramie fabrics as reinforcement. The self-assembly of the flame retardant coating on the fabric surface endowed the composites with self-extinguishing ability, and the treated composites can reach UL-94 V-0 rating during the vertical flame tests. Moreover, the interfacial adhesion of the treated composites has been enhanced. In consequence, its tensile and flexural properties have been improved and the treated composites show much higher strength and toughness compared with the untreated composites.
Co-reporter:Hongqiang Yan, Huaqing Wang, Jie Cheng, Zhengping Fang and Hao Wang
RSC Advances 2015 vol. 5(Issue 24) pp:18538-18545
Publication Date(Web):28 Jan 2015
DOI:10.1039/C4RA15035J
Iron acetylacetonate (Fe(AcAc)3) was chosen as the catalyst for a novel aromatic diamine-based benzoxazine, containing cyano group (BAPBACP). Its effect on the curing process, thermal and flammability properties of BAPBACP were investigated. The results indicated that without Fe(AcAc)3, the ring-opening polymerization of the BAPBACP monomer occurred and an arylamine Mannich bridge structure was formed at the low curing temperature stage; and then the cyclotrimerization of the cyano group followed at the high curing temperature stage, but the cyano group was not fully cyclotrimerized even after curing at 350 °C for 0.5 h. The addition of 3.5% Fe(AcAc)3 speeded up the curing reaction and the cyano group was fully cyclotrimerized at 350 °C. Thermogravimetric analysis and microscale combustion calorimetry results showed that the poly(BAPBACP) resins possess excellent thermal and flammability properties due to the existence of the arylamine Mannich bridge structure and triazine ring in their crosslinked structure.
Co-reporter:Li Zhao, Hongqiang Yan, Zhengping Fang, Jing Wang, Hao Wang
Polymer Degradation and Stability 2015 Volume 121() pp:11-17
Publication Date(Web):November 2015
DOI:10.1016/j.polymdegradstab.2015.08.007
Flame-retardant coatings were applied to ramie fabric. These consisted of oppositely-charged polyelectrolyte polyethyleneimine (PEI) and ammonium polyphosphate (APP). Application was made using, both a spray-assisted layer-by-layer (LBL) technique and by the conventional dipping LBL method. Thermogravimetric analysis showed that all the coated fabrics left two to three times as much residual char as did uncoated ones. Use of the spraying method was able to achieve the similar thermal stabilization at fewer bilayer number in coating that compared with the dipping method. Additionally, spraying also exhibited a more obvious reduction in both heat release capacity and peak heat release rate in a microscale combustion calorimeter test and cone calorimetry. The cloth acquired the same self-extinguishing property during the vertical flame test and resulted in a more compact and intact char residues. These results demonstrate that the spray-assisted LBL technique represents a relatively efficient and practical alternative to the conventional dipping LBL technique for imparting flame-retardant behavior to ramie fabric.
Co-reporter:Shiya Ran, Zhenghong Guo, Chao Chen, Liping Zhao and Zhengping Fang
Journal of Materials Chemistry A 2014 vol. 2(Issue 9) pp:2999-3007
Publication Date(Web):2013/11/29
DOI:10.1039/C3TA14179A
Multiwalled carbon nanotube (MWNT) bridged cerium phenylphosphonate (CeHPP) hybrids (Ce-MWNTs) were facilely prepared through the in situ introduction of MWNTs into the hydrothermal reaction system of CeHPP, aiming at enhancing the flame retardancy of the polymer. Morphological observations indicated that the MWNTs acted as bridges to connect CeHPP lamellas to form a consecutive structure. Moreover, due to the good dispersion of CeHPP and the acting force between CeHPP and the MWNTs, the hybrids were dispersed uniformly resisting the strong intermolecular attractions. The hybrids led to a reduction in the peak heat release rate (PHRR) of the conventional flame retardant high-density polyethylene (HDPE) composite and improved the UL-94 grade from V-2 to V-0, indicating that they could confer a better flame retardancy on HDPE compared to the CeHPP or MWNTs alone. The results of the pyrolysis products and the morphology of the chars gave the evidence that Ce-MWNTs could enhance the physical barrier effect to retard the vaporization of flammable gases and the transfer of heat because of the mutual complementarity of the CeHPP and MWNTs.
Co-reporter:Hongqiang Yan, Huaqing Wang, and Zhengping Fang
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 51) pp:19961-19969
Publication Date(Web):December 4, 2014
DOI:10.1021/ie504070t
Flame retardant ramie/benzoxazine resin laminates were prepared and modified by ammonium polyphosphate (APP) and a nitrogen–phosphorus flame retardant (NEWRAY911). The results showed that the limiting oxygen index (LOI) values of the ramie/benzoxazine laminates could be ameliorated by the addition of APP, but did not achieve V0 level in UL94 test. Their mechanical strengths were also partially damaged. To improve the flame retardancy and reduce the mechanical damage to laminates, ramie fabric was modified by NEWRAY911 before compounding. The LOI value of the laminate made by flame retardant ramie fabric could be increased to 44.8%, and the laminates achieved V0 level in UL94 test. Compared to the unmodified laminates, the flame retarding modification of the fabric helped to improve the mechanical properties of laminates. The mechanism of flame retardancy of these laminates was investigated further by thermogravimetric analysis coupled with infrared spectroscopy, microscale combustion calorimetry measurements and scanning electron microscopy.
Co-reporter:Tao Zhang, Hongqiang Yan, Mao Peng, Lili Wang, Hongliang Ding and Zhengping Fang
Nanoscale 2013 vol. 5(Issue 7) pp:3013-3021
Publication Date(Web):06 Feb 2013
DOI:10.1039/C3NR34020A
A new flame retardant nanocoating has been constructed by the alternate adsorption of polyelectrolyte amino-functionalized multiwall carbon nanotube (MWNT-NH2) and ammonium polyphosphate (APP) onto flexible and porous ramie fabric. Scanning electron microscopy indicates that the adsorbed carbon nanotube coating is a randomly oriented and overlapped network structure, which is a promising candidate for flame retardancy applications. Attenuated total reflection Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis confirm that the APP is successfully incorporated into the multilayers sequentially. Assessment of the thermal and flammability properties for the pristine and nanocoated ramie fabrics shows that the thermal stability, flame retardancy and residual char are enhanced as the concentration of MWNT-NH2 suspension and number of deposition cycles increases. The enhancements are mostly attributed to the barrier effect of intumescent network structure, which is composed of MWNT-NH2 and the absorbed APP.
Co-reporter:Zhenhu Cao, Yan Zhang, Liping Zhao, Mao Peng, Zhengping Fang, Martin Klatt
Journal of Analytical and Applied Pyrolysis 2013 Volume 102() pp:154-160
Publication Date(Web):July 2013
DOI:10.1016/j.jaap.2012.12.030
Zinc N,N′-piperazinebis(methylenephosphonic acid) (PPMPA-Zn) was melt blended with high-density polyethylene-g-maleic anhydride (HDPE-MA) to fabricate flame-retardant HDPE-MA/PPMPA-Zn composites. The thermal stability and flame retardancy of the composites were investigated by thermogravimetric analysis (TGA) and cone calorimetry. The incorporation of PPMPA-Zn did not appreciably increase the thermal stability of HDPE-MA, but the residual char content increased to 18.7% when the content of PPMPA-Zn reached 25 wt%. X-ray diffraction and Raman spectroscopy tests showed that the residual char was composed mainly of Zn(PO3)2, Zn11(HPO3)8(OH)6 and amorphous graphite. Scanning electron microscopy (SEM) images of samples collected after cone calorimetric tests also confirmed the formation of char in the sample with 25 wt% PPMPA-Zn loading in HDPE-MA, and the char layer acted as a compact and intact physical barrier in the condensed phase. Even at a loading as low as 5 wt% PPMPA-Zn, the peak value of the heat release rate (PHRR) was reduced by 38% compared with that of pure HDPE-MA. In contrast to other intumescent flame retardants, the introduction of PPMPA-Zn enhanced not only the flame retardancy but also the mechanical properties of HDPE-MA. For example, the yield strength and Young's modulus of HDPE-MA with 5 wt% PPMPA-Zn were 125% and 128% higher, respectively, than those of the pure HDPE-MA matrix.Highlights► A novel metal chelate (PPMPA-Zn) containing phosphorus, nitrogen and zinc was synthesized. ► PPMPA-Zn can form an expanded intact char in fire. ► PPMPA-Zn increased both flame retardancy and mechanical properties of polyethylene.
Co-reporter:Tao Zhang, Hongqiang Yan, Lili Wang, and Zhengping Fang
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 18) pp:6138
Publication Date(Web):April 15, 2013
DOI:10.1021/ie3031554
Self-extinguishing multilayer coatings consisting of polyelectrolyte polyethylenimine (PEI) and ammonium polyphosphate (APP) have been constructed by the layer-by-layer assembly technique onto flexible and porous ramie fabric. Attenuated total reflection Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis directly confirmed that PEI and APP were successfully incorporated onto the surface of ramie fabric sequentially. Assessment of the thermal and flammability properties for the coated ramie fabrics showed that the char residue at temperatures ranging from 400 to 600 °C during thermogravimetric analysis (TGA) and the self-extinguishing ability during vertical flame test were significantly enhanced as compared with the pristine sample, which showed strong dependency on the number of deposited layers, especially on the concentration collocation of both polyelectrolytes. This work provided a simple but effective method for the controlled formation of self-extinguishing intumescent coating on ramie fabric and can be applied to other cellulose systems.
Co-reporter:Yan Zhang;Xiaoling Chen
Journal of Applied Polymer Science 2013 Volume 128( Issue 4) pp:2424-2432
Publication Date(Web):
DOI:10.1002/app.38382
Abstract
A novel flame retardant system, ammonium polyphosphate (APP), and expandable graphite (EG) with a new carbon source, poly(diphenolic phenyl phosphate) (poly(DPA-PDCP)), derived from biomass has been proven to be effective in preventing melting drip and improving flame retardancy of acrylonitrile–butadiene–styrene copolymer (ABS) in this study, which was manifested by limiting oxygen index (LOI) and vertical flammability (UL-94) tests. The optimal synergy was exhibited at a loading of 30 wt % of three flame retardants in a proper ratio (APP/poly(DPA-PDCP)/EG = 12/3/15). Thermogravimetric analysis result indicated the char residue and the thermal stability could be enhanced because of the synergistic effect of APP/poly(DPA-PDCP)/EG, which is elaborated by a hypothesis of flame retardancy mechanism of the three components. The morphologies of cross-section and char residue by SEM were also described. The dynamic mechanical analysis implied that APP/poly(DPA-PDCP)/EG together can enhance the dynamic mechanical property of ABS. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Lili Wang;Tao Zhang;Hongqiang Yan;Mao Peng
Journal of Applied Polymer Science 2013 Volume 129( Issue 5) pp:2986-2997
Publication Date(Web):
DOI:10.1002/app.39015
Abstract
Transition-metal-ion-doped flame-retardant coatings were constructed on the surface of ramie fabrics by a layer-by-layer (LbL) assembly technique to investigate possible cooperative actions that could improve the fabric's flame-retardant efficiency. We found that these functional coatings, consisting of poly(vinylphosphonic acid) (the anionic layer) and branched polyethylenimine/cupric or zinc ions (the cationic layer), improved the fire retardancy of the ramie fabrics remarkably. Attenuated total reflectance–Fourier transform infrared (FTIR) spectroscopy and energy dispersive X-ray spectroscopy demonstrated the successful LbL assembly process and the incorporation of metal ions into the coating. Thermogravimetric analysis coupled with FTIR spectrometry, vertical flame testing, and microscale combustion calorimetry confirmed the improved thermal stability and reduced flammability of the coated ramie fabrics. All of the results show that the metal-ion-doped flame-retardant coatings not only dramatically increased the residues but also retained the original weave structure and fiber morphology of ramie fabrics well. The enhanced flame-retardant efficiency may have been caused by the lower decomposition temperature of the flame-retardant coating, as promoted by cupric and zinc ions, and as a result, may have helped the flame-retardant activity to take place earlier. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Yan Liu, Yan Zhang2, Zhenhu Cao, and Zhengping Fang
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 34) pp:11059
Publication Date(Web):August 9, 2012
DOI:10.1021/ie301562b
Three novel intumescent flame retardants (IFRs), polyphosphate esters (designated as PDP, PEP, and PPP), were synthesized by reacting phenyl dichlorophosphate with three bis-hydroxy azomethine monomers through interfacial polycondensation. The polyphosphate esters were characterized by hydrogen nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). Thermal stability and flammability properties of ethylene vinyl acetate copolymer (EVA)/30%IFRs blends were investigated by thermogravimetric analysis (TGA), limited oxygen index (LOI), and microscale combustion calorimeter (MCC). The EVA/IFRs blends exhibited high thermal stabilities, and char yields at 600 °C were 11–19% in nitrogen. The results from MCC indicated that the addition of PPP to EVA reduced the PHRR by about 33%, while the LOI values increased from 19 to 22. Scanning electron microscope (SEM) observation results indicated that the existence of the tight charred layer on the surface of the residues was responsible for the improvement of the flame retardancy of EVA.
Co-reporter:Zhenhu Cao;Pingan Song;Yuanyuan Xu;Yan Zhang;Zhenghong Guo
Journal of Applied Polymer Science 2012 Volume 126( Issue 5) pp:1546-1555
Publication Date(Web):
DOI:10.1002/app.36898
Abstract
A facile method to encapsulate the reduced graphene oxide (RGO) sheets physically with polyethylene (PE) wax was developed. The graphene oxide sheets were first wrapped with polyethylene wax, and reduced by hydrazine hydrate. The structure of the wrapped RGO was confirmed by means of Fourier transform infrared spectroscopy, X-ray diffraction (XRD), and Raman spectroscopy. The PE wax-wrapped RGO sheets were melt blended with PE to prepare PE/RGO nanocomposites. Transmission electron microscopy and XRD studies showed that this method could provide uniform dispersion of RGO sheets in the PE matrix. Scanning electron microscopy and Raman spectroscopy indicated that there was a strong interfacial interaction between the PE wax-wrapped RGO sheets and PE matrix. Addition of 1 wt % RGO sheets in PE matrix led to a 48% increment in the yield stress and 118% increment in the Young's modulus, respectively. However, the elongation at break decreased with increasing RGO sheets loading content. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Co-reporter:Yajun Chen;Zhenghong Guo
Polymer Engineering & Science 2012 Volume 52( Issue 2) pp:390-398
Publication Date(Web):
DOI:10.1002/pen.22094
Abstract
This article studies the relationship between the distribution of organically modified montmorillonite (OMMT) and the flammability of flame retardant polypropylene which consists of polypropylene (PP), brominated epoxy resin-antimony oxide (BER-AO) and OMMT. Polypropylene-graft-maleic anhydride (PP-g-MAH) was used to increase the polarity of PP and aid the dispersion of OMMT. Two model systems, PP/BER-AO/OMMT and PP/PP-g-MAH/BER-AO/OMMT composites, have been prepared by melt blending. TEM studies reveal a significant change in the distribution of OMMT for these two systems. For the first composites, OMMT platelets are aggregated in the BER-AO domains, whereas for the second composites, OMMT platelets are dispersed in the PP matrix. The flame retardant properties of the second composite reflected by UL 94 vertical burning test and cone calorimetry are better than that of the first one. When OMMT platelets aggregate in BER-AO domains as in the first composite, the BER-AO associated with OMMT may agglomerate into long ribbon-like structures during burning, inducing uneven distribution of BER-AO. As a result, loose and uneven residues are formed at the end of combustion. In comparison, OMMT platelets dispersed in polymer matrix are more efficient at stabilizing the polymer and preventing aggregation of BER-AO during burning, which induce thick and uniform char layers at the end of combustion. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers
Co-reporter:Pingan Song, Liping Zhao, Zhenhu Cao and Zhengping Fang
Journal of Materials Chemistry A 2011 vol. 21(Issue 21) pp:7782-7788
Publication Date(Web):08 Apr 2011
DOI:10.1039/C1JM10395D
In the present study, the effects of covalently functionalized carbon nanotubes (CNTs) decorated with C60 (abbr. C60-d-CNT) on thermal, flame retardancy and mechanical properties of polypropylene (PP) are investigated. Compared with pristine CNTs, the C60-d-CNT is more easily dispersed in the PP matrix through reactive compatibilization. With the incorporation of C60-d-CNT, thermal oxidation degradation of PP is considerably delayed. Compared to PP, at 1.0 wt% loading of C60-d-CNT, the initial degradation temperature (T5) and maximum weight loss temperature (Tmax) in air are enhanced by 68 °C and 87 °C, respectively. Furthermore, incorporating 1.0 wt% C60-d-CNT can remarkably reduce the peak heat release rate (PHRR) by 71% relative to that of PP, and slow down the combustion process to some extent. The free-radical trapping effect of C60 and the CNTs network are responsible for the improved thermal and flame retardancy properties. Meanwhile, addition of C60-d-CNT also causes enhanced mechanical properties of PP nanocomposites to a certain degree.
Co-reporter:Baoxian Du;Haiyun Ma
Polymers for Advanced Technologies 2011 Volume 22( Issue 7) pp:1139-1146
Publication Date(Web):
DOI:10.1002/pat.1914
Recent advances in flame retardant polymers have centered on the flame retardancy of nano-fillers contained polymer nanocomposites. Among which, organo-clay (OMMT), layered double hydroxides (LDHs), polyhedral oligomeric silsesquioxane (POSS), and carbon nanotubes (CNTs) have been reported and proved to be effective flame retardants for variable polymers. In this paper, a systematical study was executed on flame retarded polypropylene (PP) composites containing intumescent flame retardant (IFR) and the most popular nano-fillers. Dispersion of the nano-fillers was characterized by using transmission electron microscopy (TEM), the results revealed that all nano-fillers dispersed homogeneously in PP matrix. The effects of nano-fillers on thermal stability and flammable of PP were investigated by thermogravimetry (TG) and cone calorimetry tests, respectively. The results indicated that different nano-fillers played different roles in thermal and flammability properties of composites. PP composites with OMMT gave the best reductions in heat release rate (PHRR) and endowed PP with relatively better flame retardancy. Copyright © 2011 John Wiley & Sons, Ltd.
Co-reporter:Pingan Song, Zhenhu Cao, Yuanzheng Cai, Liping Zhao, Zhengping Fang, Shenyuan Fu
Polymer 2011 Volume 52(Issue 18) pp:4001-4010
Publication Date(Web):18 August 2011
DOI:10.1016/j.polymer.2011.06.045
Despite the great potential of graphene as the nanofiller, to achieve homogeneous dispersion remains the key challenge for effectively reinforcing the polymer. Here, we report an eco-friendly strategy for fabricating the polymer nanocomposites with well-dispersed graphene sheets in the polymer matrix via first coating graphene using polypropylene (PP) latex and then melt-blending the coated graphene with PP matrix. A ∼75% increase in yield strength and a ∼74% increase in the Young’s modulus of PP are achieved by addition of only 0.42 vol% of graphene due to the effective external load transfer. The glass transition temperature of PP is enhanced by ∼2.5 °C by incorporating only 0.041 vol% graphene. The thermal oxidative stability of PP is also remarkably improved with the addition of graphene, for example, compared with neat PP, the initial degradation temperature is enhanced by 26 °C at only 0.42 vol% of graphene loading.We created the polypropylene (PP)/exfoliated graphene nanocomposites via melt-blending by first coating graphene sheets with PP latex. Compared with neat PP, a ∼75% increase in yield strength and a ∼74% increase in the Young’s modulus are achieved by addition of only 0.42 vol% of graphene sheets due to the effective external load transfer.
Co-reporter:Lina Liu, Zhengping Fang, Aijuan Gu, Zhenghong Guo
Composites Part B: Engineering 2011 Volume 42(Issue 8) pp:2117-2122
Publication Date(Web):December 2011
DOI:10.1016/j.compositesb.2011.05.006
Atmospheric pressure filamentary dielectric barrier discharge (APDBP) treatment was adopted to modify the surface of the multi-walled carbon nanotubes (MWCNTs), altering the miscibility of MWCNTs with bismaleimide (BMI) matrix and the effects of this treatment on friction and wear properties of MWCNTs/BMI composites were investigated. Dynamic mechanical analysis (DMA), scanning electron microscope (SEM) images of the fractured surface and the worn surface were adopted to figure out the possible friction and wear mechanism of the composite. It is found that BMI composite with APDBD treated MWCNTs exhibits a lower friction coefficient value and a lower wear loss rate value than the composite with original MWCNTs, which can be related to the higher degree of crosslink of the resin and also better interfacial adhesion between MWCNTs and the BMI matrix.
Co-reporter:Lina Liu;Aijuan Gu;Zhenghong Guo
Tribology Letters 2011 Volume 42( Issue 1) pp:59-65
Publication Date(Web):2011 April
DOI:10.1007/s11249-011-9749-y
Multiwalled carbon nanotubes (MWCNTs) were functionalized and were used as additives in paraffin oil to improve its lubrication effect for bismaleimide resin. The tribological behavior of bismaleimide resin lubricated by the paraffin oil filled with the functionalized carbon nanotubes was investigated by friction and wear tester. The wear surface of the resin with steel ball as tribopair was analyzed by means of scanning electron microscopy (SEM). It was found that the addition of this kind of functionalized MWCNTs effectively reduced the friction coefficient. An optimal additive concentration existed in the system and was found to be 0.025 wt%. A lubrication model for the resin and steel ball system was postulated and it was the isolating effect and bearing structure of f-MWCNTs that played a key role in friction and wear reduction.
Co-reporter:HaiYun Ma;PingAn Song
Science China Chemistry 2011 Volume 54( Issue 2) pp:302-313
Publication Date(Web):2011 February
DOI:10.1007/s11426-010-4196-4
Polymer nanocomposites are a new class of flame retarded materials which have attracted much attention and considered as a revolutionary new flame retardant approach. A very small amount of nano flame retardants (normally < 5 wt%) can significantly reduce the heat release rate (HRR) and smoke emission (SEA) during the combustion of polymer materials. Moreover, the addition of nano flame retardants can also improve the mechanical properties of polymer materials compared with the deterioration of traditional flame retardants. This paper reviews the recent development in the flame retardant field of polymer nanocomposites and also introduces the related research in our lab. The challenges and problems are discussed and the future development of flame retarded polymer nanocomposites is prospected.
Co-reporter:Yajun Chen;Zhenghong Guo
Journal of Applied Polymer Science 2010 Volume 118( Issue 1) pp:152-158
Publication Date(Web):
DOI:10.1002/app.32452
Abstract
Polystyrene (PS) was flame retarded with a polymeric intumescent flame retardant, poly(diaminodiphenyl methane spirocyclic pentaerythritol bisphosphonate) (PDSPB), and in situ compatibilized with styrene-maleic anhydride (SMA) copolymer. Compatibilization reaction was verified by IR spectroscopy and gel content measurement. Electron microscopy images showed that compatibilization could considerably reduce the size of the flame retardant domains and improve the interfacial adhesion between PS and PDSPB. With the same PDSPB loading (20 wt %), addition of 5, 10, and 20 wt % SMA increased the impact strength of the flame retarded PS by about 29, 103, and 201%, respectively. Compared with PS/PDSPB sample, addition of 5 wt % of SMA improved the limiting oxygen index from 23.8 to 24.2 and reduced the peak heat release rate (PHRR) of the blend by 18.3%. However, further increment of SMA content deteriorated the flame retardancy of the blend. It was found that the NH2 groups changed into more stable imide groups at high temperature, causing the absence of gas source. Therefore, the intumescent char could not be formed during combustion process, which was the main reason for the deteriorate effect of flame retardancy at high SMA loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Yajun Chen;Chunzhuang Yang;Yu Wang;Zhenghong Guo;Yan Zhang
Journal of Applied Polymer Science 2010 Volume 115( Issue 2) pp:777-783
Publication Date(Web):
DOI:10.1002/app.31068
Abstract
Different formulations were designed to evaluate the effect of organically modified clay (DK4) on the combustion behavior of polystyrene (PS) containing an intumescent flame retardant, poly(4,4-diaminodiphenyl methane spirocyclic pentaerythritol bisphosphonate) (PDSPB). The results of transmission electron microscopy reveal that DK4 selectively dispersed in the PDSPB phase. An investigation of thermogravimetric analysis revealed that the thermal stability of PS resin showed no obvious change with the addition of PDSPB and DK4, but the residue increased. From the results of cone calorimetry, we observed that there were two steps during combustion. The dispersion of DK4 played an important role in improving the thermal stability and the flammability of the PS/PDSPB/DK4 nanocomposites. In the first step, DK4 was restricted in the PDSPB phase; there was no synergistic effect. A synergistic effect occurred in the second step when clay had a homogeneous distribution, in which the peak heat release rates were reduced by about 40 and 61% compared to the pure PS. A model of combustion behavior was developed according to these results. The synergistic mechanism was caused by the formation of the silicoaluminophosphate (SAPO) structure formed by reactions between PDSPB and DK4. Field emission scanning electron microscopy characterization showed that such an SAPO structure led to a ceramic-like residue after burning. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Yu Shen;Zhenghong Guo;Jie Cheng
Journal of Applied Polymer Science 2010 Volume 116( Issue 3) pp:1322-1328
Publication Date(Web):
DOI:10.1002/app.31540
Abstract
Carbon nanotubes with different functional groups were prepared and then incorporated into the poly(2,6-dimethyl-1,4-phenylene oxide)/polyamide 6 (PPO/PA6) blend via melt blending. The influence of different carbon nanotubes on the morphology and properties of the blend was studied. The results show that addition of pristine CNTs, CNTs-OH, CNTs-NH2 leads to the evolution of the phase structure of PPO/PA6 (mass ratio: 60/40) blend from sea-island to cocontinuous, whereas incorporation of CNTs-COOH does not change the blend morphology due to serious aggregation of the carbon nanotubes. Incorporating different CNTs into PPO/PA6 blend increases the tensile modulus and storage modulus of the blends, whereas decreases slightly the tensile strength. At the same time, the glass transition temperatures (Tg) of PA6 and PPO are enhanced. ΔTg, the gap between the Tg of PA6 and PPO, decreases with the addition of carbon nanotubes due to the stronger interaction of carbon nanotubes with PA6 than PPO. A similar tendency was found in the storage modulus (G′) and complex viscosity (η*) of the composites. The dispersion state of different carbon nanotubes and their interaction with polymer components are different, which causes the different confinement effect to the macromolecular chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Bing-tao Wang;Yan Zhang;Ping-an Song
Chinese Journal of Polymer Science 2010 Volume 28( Issue 3) pp:405-415
Publication Date(Web):2010 May
DOI:10.1007/s10118-010-9032-y
Biodegradable aliphatic/aromatic copolyesters, poly(butylene terephthalate-co-lactate) (PBTL) were prepared via direct melt polycondensation of terephthalic acid (TPA), 1,4-butanediol (BDO) and poly(L-lactic acid) oligomer (OLLA). The effects of polymerization time and temperature, as well as aliphatic/aromatic moiety ratio on the physical and thermal properties were investigated. The largest molecular weight of the copolyesters was up to 64100 with molecular weight distribution index of 2.09 when the polycondensation was carried out at 230°C for 6 h. DSC, XRD, DMA and TGA analysis clearly indicated that the degree of crystallinity, glass-transition temperature, melting point, decomposition temperature, tensile strength, elongation and Young’s modulus were influenced by the ratio between TPA and OLLA in the final copolyesters. Hydrolytic degradation results demonstrated that the incorporation of biodegradable lactate moieties into the aromatic polyester could efficiently improve hydrolytic degradability of the copolymer even though it still had many aromatic units in the main chains.
Co-reporter:Baoxian Du, Zhenghong Guo, Zhengping Fang
Polymer Degradation and Stability 2009 Volume 94(Issue 11) pp:1979-1985
Publication Date(Web):November 2009
DOI:10.1016/j.polymdegradstab.2009.07.024
The thermal and flame performances of intumescent flame retarded polypropylene (PP/IFR) composites with organically modified clay or sodium dodecyl sulfonate intercalated layered double hydroxide (SDS-LDH) were studied. The organo-clay particles were partially exfoliated in the PP matrix, while intercalation and aggregation was obtained for SDS-LDH. Incorporation of SDS-LDH improved the thermal stability and flame retardancy of the intumescent flame retarded PP composite in the early stage of heating and combustion; while the effects of organo-clay came into play in the middle-later stage. Differences in degradation pathway of clay and LDH were responsible for the above phenomenon which bore important implication for the barrier mechanism. The introduction of organo-clay into PP/IFR not only increased the char residue, but also formed compact and folded morphology of char residue which provided more effective protect for underlying materials against heat and oxygen relative to LDH, thus improved the flame retardancy of intumescent flame retarded PP samples more efficiently.
Co-reporter:Yan Zhang, Bing Tao Wang, Zheng Hong Guo, Jie Chen, Zheng Ping Fang
Chinese Chemical Letters 2009 Volume 20(Issue 11) pp:1348-1352
Publication Date(Web):November 2009
DOI:10.1016/j.cclet.2009.05.013
In situ melt polycondensation was proposed to prepare biodegradable aliphatic–aromatic copolyesters/nano-SiO2 hybrids based on terephthalic acid (TPA), poly(l-lactic acid) oligomer (OLLA), 1,4-butanediol (BDO) and nano-SiO2. TEM and FT-IR characterizations confirmed that TPA, OLLA and BDO copolymerized to obtain biodegradable copolyesters, poly(butylene terephthalate-co-lactate) (PBTL), and the abundant hydroxyl groups on the surface of nano-SiO2 provided potential sites for in situ grafting with the simultaneous resulted PBTL. The nano-SiO2 particles were chemically wrapped with PBTL to form PBTL/nano-SiO2 hybrids. Due to the good dispersion and interfacial adhesion of nano-SiO2 particles with the copolyester matrix, the tensile strength and the Young's modulus increased from 5.4 and 5.6 MPa for neat PBTL to 16 and 390 MPa for PBTL/nano-SiO2 hybrids with 5 wt.% nano-SiO2, respectively. The mechanical properties of PBTL/nano-SiO2 hybrids were substantially improved.
Co-reporter:Zhengping Fang;Lina Liu;Aijuan Gu;Xinyu Wang;Zhenghong Guo
Polymers for Advanced Technologies 2009 Volume 20( Issue 11) pp:849-856
Publication Date(Web):
DOI:10.1002/pat.1345
Abstract
Through the functionalization of multiwalled carbon nanotubes (MWCNTs) by 0,0′-diallylbisphenol A (DBA), the interface situation between MWCNTs and bismaleimide (BMI) was improved, as detected by scanning electron microscope (SEM) and dynamic mechanical analysis (DMA). The improved interface situation was considered to be the main reason for the huge increased microhardness value and greatly improved the microtribological property of MWCNTs/BMI composites. Besides, the wear mechanism for the composite was also believed to be related to the interfacial situation. The rough wavelike worn surface of pure BMI resin is attributed to its poor load capacity. The smoother waterfall-shape worn surface of MWCNTs/BMI is related to the interface formed by the addition of MWCNTs while the ultrasmooth worn surface of DBA modified MWCNTs/BMI is due to the greatly improved interfacial interaction of the composite. Copyright © 2008 John Wiley & Sons, Ltd.
Co-reporter:Lina Liu;Aijuan Gu;Zhenghong Guo
Journal of Applied Polymer Science 2009 Volume 113( Issue 6) pp:3484-3491
Publication Date(Web):
DOI:10.1002/app.30156
Abstract
Original multiwalled carbon nanotubes (O-MWCNTs) and aminofunctionalized ethylenediamine-treated multiwalled carbon nanotubes (MWCNTs-EDA) were mixed with bismaleimide (BMI) resin to prepare O-MWCNT/BMI and MWCNT-EDA/BMI composites, respectively. Raman spectroscopy, thermogravimetric analysis, and infrared spectroscopy were used to investigate the influence of aminofunctionalization on the multiwalled carbon nanotube (MWCNT) framework. Dynamic mechanical analysis, scanning electron microscopy images of the fractured surface, and field emission scanning electron microscopy of the worn surface were used to determine the possible friction and wear mechanisms of the system. The MWCNT-EDA/BMI composite exhibited a higher friction coefficient value and a lower wear loss rate value than the O-MWCNT/BMI composite, which was attributed to the larger number of defects caused by the aminofunctionalization of the MWCNTs, the stronger interfacial adhesion formed between the MWCNTs-EDA and the BMI resin, and the better dispersive state of the MWCNTs-EDA in the BMI matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Hai-Yun Ma;Li-Fang Tong;Zhong-Bin Xu;Zheng-Ping Fang
Advanced Functional Materials 2008 Volume 18( Issue 3) pp:414-421
Publication Date(Web):
DOI:10.1002/adfm.200700677
Abstract
An intumescent flame retardant, poly(diaminodiphenyl methane spirocyclic pentaerythritol bisphosphonate) (PDSPB) has been covalently grafted onto the surfaces of multiwalled carbon nanotubes (MWNTs) to obtain MWNT-PDSPB and according nanocomposites were prepared via melt blending. After high density PDSPB (65 wt %) were attached to the MWNTs, core-shell nanostructures with MWNTs as the hard core and PDSPB as the soft shell were formed. The resultant MWNT-PDSPB was soluble and stable in polar solvents, such as DMF. The optical microscopy and TEM results showed that the functionalized MWNTs can achieve better dispersion in ABS matrix. The linear viscoelastic behavior indicated that MWNT-PDSPB can form network structure at very low nanotube loading than un-functionalized MWNTs. The results of flammability showed that better flame retardancy was obtained for ABS/MWNT-PDSPB nanocomposites due to the better dispersion of MWNT-PDSPB in ABS matrix. The flammability of the composites is strongly dependent on the network structure of nanotubes which reduces the diffusion of volatile combustible fragments generated by polymer degradation which diffuse towards the surface of the burning polymer to evaporate to feed the flame. The grafting of intumescent flame retardant of PDSPB can improve both the dispersion of nanotubes in polymer matrix and flame retardancy of the nanocomposites.
Co-reporter:Pingan Song, Zhengping Fang, Lifang Tong, Yongming Jin, Fengzhu Lu
Journal of Analytical and Applied Pyrolysis 2008 Volume 82(Issue 2) pp:286-291
Publication Date(Web):July 2008
DOI:10.1016/j.jaap.2008.04.008
A novel oligomeric phosphorus–nitrogen containing intumescent flame retardant, poly(4,4-diamino diphenyl methane-O-bicyclicpentaerythritol phosphate-phosphate) (PDBPP), was synthesized and characterized. Effects of metal chelates on flame retardancy of polypropylene (PP)/PDBPP systems were studied and the results showed that the presence of metal chelates considerably enhanced the fire retardant performance as evidenced by the increase of LOI values and a great reduction in peak heat release rate of PP/PDBPP system. Raman spectroscopy, infrared spectroscopy and scanning electron microscopy demonstrated that metal chelates could react with polyphosphoric acid, a decomposition product of PDBPP, to form crosslinked network. Through salt bridges a more compact char layer was formed which was responsible for the improved thermal and flame retardancy properties of PP/PDBPP system.
Co-reporter:Pingan Song;Lifang Tong
Journal of Applied Polymer Science 2008 Volume 110( Issue 1) pp:616-623
Publication Date(Web):
DOI:10.1002/app.28689
Abstract
Polypropylene (PP)/clay nanocomposites were prepared by melt-compounding PP with organomontmorillonite (OMT), using maleic anhydride grafted polypropylene (PP-g-MA) as the primary compatibilizer and N-imidazol-O-(bicyclo pentaerythritol phosphate)-O-(ethyl methacrylate) phosphate (PEBI) as the cointercalating monomer. X-ray diffraction patterns indicated that the larger interlayer spacing of OMT in PP was obtained due to the cointercalation monomer having a large steric volume and the d-spacing further increased with the addition of PP-g-MA, as evidenced by transmission electron microscopy. Thermogravimetric analysis revealed that the PEBI-containing PP nanocomposites exhibited better thermal stability than PEBI-free PP composites. Dynamic mechanical analysis demonstrated that the storage modulus was significantly enhanced, and the glass transition temperature (Tg) shifted slightly to low temperature with the incorporation of clay for PP/OMT hybrids. PEBI-containing PP/OMT composites gave a lower Tg value because of the strong internal plasticization effect of PEBI in the system. Cone calorimetry showed that the flame-retardancy properties of PP nanocomposites were highly improved with the incorporation of PEBI. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Yan Zhu;Yuzhen Xu;Lifang Tong;Zhongbin Xu
Journal of Applied Polymer Science 2008 Volume 110( Issue 5) pp:3130-3139
Publication Date(Web):
DOI:10.1002/app.28927
Abstract
The immiscible polypropylene (PP)/polystyrene (PS) blend was prepared via melt compounding and the preferential intercalation behavior of clay was investigated by wide angle X-ray diffraction (XRD) and transmission electron microscope (TEM). It was found that the clay platelets initially located in the PS phase in PP/PS/Clay composites and PS chains intercalated into the clay layers. However, all clay migrated from the PS phase to the modified PP phase after introducing polar maleic anhydride group (MAH) to PP chains. Interestingly, most of clay migrated from the modified PP phase to the modified PS phase again when PS matrix was modified with sulfonic group, and some enriched in the interphase region. The interaction energy density (B) of the blends was determined by combining the melting point variation with the ternary interaction model for heat of mixing. It was found that the value of B decreased with the introduction of polar group (MAH or sulfonic group), indicating that the polarization of PP and PS can enhance interaction between clay platelet and polymer component. Different interaction between clay platelet and polymer component leads to the preferential intercalation behavior. The higher polarity of the polymer generates higher interaction between clay and polymer component as well as results in stronger preferential intercalating ability. Moreover, the results of FTIR spectra after extraction of all samples gave additional explanation of the preferential intercalation behavior of clay in the immiscible PP/PS blends. On the basis of the results of the measurement mentioned above, a possible mechanism was proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Xiao Yun Fu, Zheng Ping Fang, Hai Tang Yang, Li Fang Tong
Chinese Chemical Letters 2008 Volume 19(Issue 6) pp:655-657
Publication Date(Web):June 2008
DOI:10.1016/j.cclet.2008.04.015
In this work, the preparation of α,ω-dichloride-terminated multi-vinyl branched siloxane 1 (yield: 57.1%) used for self-healing polymer composites were synthesized via ring-opening of 1,3,5,7-tetravinyl-1,3,5,7-tetramethyl-cyclotetrasiloxane (D4Vi) in the presence of vinylmethydichlorosilane (VM–32). 1 was hydrogenated by aluminum lithium hydride (LiAlH4) to get self-healing monomer 2 (yield: 79.8%) which contained both Si–H bonds and Si–vinyl bonds. Then hydrosilation occurred between these two bands and finally silicone 3 was obtained, showing the potential of self-healing.
Co-reporter:Zhengping Fang, Pingan Song, Lifang Tong, Zhenghong Guo
Thermochimica Acta 2008 Volume 473(1–2) pp:106-108
Publication Date(Web):10 July 2008
DOI:10.1016/j.tca.2008.04.019
Nanocomposites based on polypropylene (PP) and fullerene C60 (in the range of 0.5–2 wt%) were prepared by melt compounding. It was observed that C60 could not only significantly enhance the thermal stability in nitrogen but also considerably delay the oxidation decomposition in air of polypropylene. Unexpectedly, the incorporation of C60 greatly reduced the heat release rate of PP and resulted in a longer time to ignition. And the free radicals-trapping mechanism of C60 was proposed for explaining the enhanced thermal properties and improved flame retardancy of PP. Therefore, C60 will be an effective flame retardant like carbon nanotubes and clay for PP.
Co-reporter:Yan Zhu;Hai-yun Ma;Li-fang Tong
Journal of Zhejiang University-SCIENCE A 2008 Volume 9( Issue 11) pp:1614-1620
Publication Date(Web):2008 November
DOI:10.1631/jzus.A0820104
In this work, polypropylene (PP)/polystyrene (PS) blends with different organoclay concentrations were prepared via melt compounding. Differing from the results of previous reports, the organoclay platelets are mostly located in the dispersed PS phase instead of the interface. The dimensions of the dispersed PS droplets are greatly reduced and apparent compatibilization effect still exists, which cannot be explained by the traditional compatibilization mechanism. A novel compatibilization mechanism, “cutting” to apparently compatibilize the immiscible PP/PS blends was proposed. The organoclay platelets tend to form a special “knife-like structure” in the PS domain under the shear stress of the continuous PP phase during compounding. The “clay knife” can split the dispersed PS domain apart and lead to the dramatic reduction of the dispersed domain size.
Co-reporter:Zhenghong Guo, Zhengping Fang, Lifang Tong, Zhongbin Xu
Polymer Degradation and Stability 2007 Volume 92(Issue 4) pp:545-551
Publication Date(Web):April 2007
DOI:10.1016/j.polymdegradstab.2007.01.012
This paper reported the degradation behaviors and thermal properties of polystyrene (PS)/polyolefin elastomer (POE) blends with AlCl3 as the catalyst of Friedel–Crafts alkylation reaction. Gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) were adopted to reveal the effects of in situ grafting reaction and degradation of blending compounds on the thermal properties of PS/POE blends. It was found that the changes in both catalyst content and blend composition influenced the competition between in situ grafting reaction and degradation, resulting in the complexity of the thermal properties of PS/POE/AlCl3 blends.
Co-reporter:Haiyun Ma, Lifang Tong, Zhongbin Xu, Zhengping Fang
Polymer Degradation and Stability 2007 Volume 92(Issue 8) pp:1439-1445
Publication Date(Web):August 2007
DOI:10.1016/j.polymdegradstab.2007.05.013
A melt blending method was used to prepare ABS/clay and ABS-g-MAH/clay nanocomposites. Cone calorimeter and advanced rheological extension system (ARES©) were employed to measure flammability and dynamic rheological properties. The main aim is to establish a relationship between the clay network structure and flammability properties of polymer nanocomposites. From the results of dynamic rheological measurements, it was found that the clay network structure was formed in ABS-g-MAH/clay nanocomposites, which strongly affected the flammability properties of the nanocomposites. The clay network improves the melt viscosity and results in restraint on the mobility of the polymer chains during combustion, which leads to significant improvement of flame retardancy for the nanocomposites.
Co-reporter:Juan Li;Yan Zhu;Fu Liu;Aijuan Gu;Lifang Tong
Journal of Applied Polymer Science 2007 Volume 105(Issue 6) pp:3531-3542
Publication Date(Web):5 JUN 2007
DOI:10.1002/app.24606
Pristine and functionalized multiwalled carbon nanotubes (MWNTs) were used to fabricate polyamide 6 (PA6) composites through melt blending. The functionalized MWNTs were obtained by grafting 1,6-hexamethylenediamine (HMD) onto the pristine MWNTs to improve their compatibility with PA6 matrix. The effect of MWNTs on the isothermal crystallization and melting behavior of PA6 was investigated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The Avrami and Lauritzen–Hoffmann equations are used to describe the isothermal crystallization kinetics. The values of the Avrami exponent found for neat PA6, the pristine MWNTs/PA6 and functionalized MWNTs/PA6 composite samples are about 4.0, 1.7, and 2.3, respectively. The activation energies are determined by the Arrhenius method, which is lower for the composites, −320.52 KJ/mol for pristine MWNTs/PA6 and −293.83 KJ/mol for functionalized MWNTs/PA6, than that for the neat PA6 (−284.71 KJ/mol). The following melting behavior reveals that all the isothermally crystallized samples exhibit triple melting endotherms at lower crystallization temperature and double melting endotherms at higher crystallization temperature. The multiple melting endotherms are mainly caused by the recrystallization of PA6 during heating. The resulting equilibrium melting temperature is lower for the composites than for neat PA6. In addition, polarizing microscopy (PLM) and small angle light scanning (SALS) were used to study the spherulite morphology. The results show that the MWNTs reduce the spherulite radius of PA6. This reduction is more significant for pristine MWNTs. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Co-reporter:Aijuan Gu;Zhongbin Xu;Chao Zhao;Lifang Tong
Journal of Applied Polymer Science 2007 Volume 106(Issue 3) pp:2008-2017
Publication Date(Web):20 JUL 2007
DOI:10.1002/app.26827
Several carbon black (CB)-filled binary polymer blends were prepared in Haake rheometer. Distribution states of CB and effect of morphology on the electric conductivity of different ternary composites were investigated. Under our experimental condition CB particles located preferentially at the interface between polymethyl methacrylate (PMMA) and polypropylene (PP) in PMMA/PP/CB composites, in high-density polyethylene (HDPE) phase in PP/HDPE/CB composites, and in Nylon6 (PA6) phase in polystyrene (PS)/PA6/CB, PP/PA6/CB, PMMA/PA6/CB, and polyacrylonitrile (PAN)/PA6/CB composites; the ternary composites in which CB particles locate at the interface of two polymer components have the highest electric conductivity when the mass ratio of the two polymers is near to 1 : 1. The ternary composites in which CB particles located preferentially in one polymer have the highest electric conductivity usually when the amount of the polymer component having CB particles is comparatively less than the amount of the polymer component not having CB particles; if the formulations of PS/PA6/CB, PP/PA6/CB, and PMMA/PA6/CB composites equaled and PA6/CB in them is in dispersed phase, PS/PA6/CB composites have the highest electric conductivity and PP/PA6/CB composites have the lowest electric conductivity; suitable amount of PS or PAN in PA6/CB composites increase the electric conductivity due in the formation of a parallel electrocircuit for electrons to transmit. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Co-reporter:Zhengping Fang;Lifang Tong;Aijuan Gu;Fu Liu;Juan Li
Journal of Applied Polymer Science 2007 Volume 106(Issue 5) pp:2898-2906
Publication Date(Web):9 AUG 2007
DOI:10.1002/app.24599
The focus of this study is to investigate the state of dispersion of different treated multiwalled carbon nanotubes (MWNTs) in polyamide 6 (PA6). The MWNTs used in composites were grafted by 1,6-hexamethylenediamine (HMD) via acid-thionyl chloride to improve their compatibility with PA6 matrix. A microstructure transformation of MWNTs is found during the treatment process. Acidification makes the MWNTs compact and grafting HMD promotes the compact structure loose again. The MWNTs after different treatment were used to fabricate MWNTs/PA6 composites through melt blending. The dispersion of different MWNTs in PA6 was observed by a combination of scanning electron microscopy, optical microscopy, and transmission electron microscopy. The results show that the amino-functionalized MWNTs are dispersed more homogeneously in PA6 than the purified MWNTs, and the poorest dispersion is achieved for acid treated MWNTs. It is indicated that the loose structure and functionalized surface of MWNTs benefit the dispersion of MWNTs in PA6. In addition, the amino-functionalization of MWNTs improves the compatibility between the MWNTs and PA6, resulting in stronger interfacial adhesion. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Co-reporter:Zhenghong Guo;Lifang Tong;Zhongbin Xu
Polymer Engineering & Science 2007 Volume 47(Issue 6) pp:951-959
Publication Date(Web):30 APR 2007
DOI:10.1002/pen.20779
To increase the compatibility of polystyrene (PS) and polyolefin elastomer (POE) blends, a Lewis acid catalyst, aluminum chloride (AlCl3), was adopted to initiate the Friedel–Crafts alkylation reaction for the formation of PS-graft-POE copolymer. Dynamic mechanical analysis indicated that PS/POE and PS/POE/AlCl3 blends are partially miscible, and the formation of PS-graft-POE copolymer increased the compatibility between PS and POE. Scanning electron microscope and transmission electron microscope results showed that the domain size of the blends decreased dramatically and the size distribution became more uniform with the addition of AlCl3. Such in situ compatibilization also induced hindrance to the macromolecular chain movement, as reflected by the results of the dynamic rheological analysis. The dynamic rheological behaviors of PS/POE and PS/POE/AlCl3 blends under different temperature showed that in situ compatibilization weakened the effects of thermooxidation on PS/POE blends. Moreover, in situ compatibilization decreased the activation energy of viscous flow and reduced the influence of temperature on PS/POE blends. POLYM. ENG. SCI., 47:951–959, 2007. © 2007 Society of Plastics Engineers
Co-reporter:Zhengping Fang;Yuzhen Xu;Lifang Tong
Polymer Engineering & Science 2007 Volume 47(Issue 5) pp:551-559
Publication Date(Web):26 MAR 2007
DOI:10.1002/pen.20675
Polyamide 6 (PA6)/HDPE/organo-bentonite (Oclay) and PA6/HDPE-grafted-acrylic acid (PEAA)/Oclay nanocomposites were prepared via melt compounding. The influence of Oclay on the morphology of composites was investigated. Scanning electron microscopy results revealed the size of the dispersed HDPE, and PEAA phase decreased with increasing Oclay content. Transmission electron microscopy and X-ray diffraction results revealed that the Oclay was predominately intercalated with some evidence of partial exfoliation. The majority of Oclay platelets were concentrated in the PA6 phase and in the interfacial region between PA6 and HDPE (PEAA). The Oclay platelets played the role of coupling species between the two polymers, increasing the interaction of the two phases in certain extent. These results were proved by FTIR and positron annihilation lifetime spectroscopy. Consequently, apparent emulsifying effect was induced. A schematic mechanism of the apparent compatibilization effect was presented. POLYM. ENG. SCI., 47:551–559, 2007. © 2007 Society of Plastics Engineers.
Co-reporter:Haiyun Ma, Zhengping Fang, Lifang Tong
Polymer Degradation and Stability 2006 Volume 91(Issue 9) pp:1972-1979
Publication Date(Web):September 2006
DOI:10.1016/j.polymdegradstab.2006.02.011
ABS/organo montmorillonite (OMT) nanocomposites and ABS/brominated epoxy resin–antimony oxide (BER–AO)/OMT nanocomposites were prepared via melt compounding. The dispersion of OMT in nanocomposites was investigated by wide-angle X-ray diffraction and transmission electron microscopy. The results revealed an intercalated structure in ABS/OMT nanocomposites and the OMT layers mainly distribute in SAN phase. However, a completely exfoliated structure was found in ABS/BER–AO/OMT nanocomposites and OMT layers preferentially located in the BER phase which indicated that the OMT platelets had a much higher affinity with brominated epoxy resin than ABS resin. Based on the above morphological results, a schematic diagram of the ABS/OMT, ABS/BER–AO/OMT nanocomposites was established. The thermal degradation behavior was characterized by thermogravimetry. The results showed that the exfoliation of OMT can enhance the thermal stability of pure ABS resin and ABS/BER blends. An increase in the limited oxygen index (LOI) value was observed with the addition of OMT and it was found that such an enhancement is closely related to the morphologies of the chars formed after combustion. A synergistic effect between OMT and BER–AO during the combustion of the nanocomposites was found and a schematic mechanism was presented.
Co-reporter:Juan Li, Lifang Tong, Zhengping Fang, Aijuan Gu, Zhongbin Xu
Polymer Degradation and Stability 2006 Volume 91(Issue 9) pp:2046-2052
Publication Date(Web):September 2006
DOI:10.1016/j.polymdegradstab.2006.02.001
This paper focuses on the thermal degradation behavior of multi-walled carbon nanotubes (MWNTs)/polyamide 6 (PA6) composites under air and nitrogen atmosphere using thermogravimetric analysis (TGA). The results show that the dispersion of amino-functionalized MWNTs (f-MWNTs) in PA6 is more homogeneous than purified MWNTs (p-MWNTs). The presence of MWNTs improves the thermal stability of PA6 under air obviously, but has little effect on the thermal degradation behavior of PA6 under nitrogen atmosphere. The activation energies for degradation under air, Ea, estimated by Kissinger method, are 153, 165 and 169 kJ/mol for neat PA6, p-MWNTs/PA6 and f-MWNTs/PA6 composites, respectively. The p-MWNTs/PA6 composites show two-step degradation not only under air but also under nitrogen atmosphere, however, neat PA6 and the f-MWNTs/PA6 composites exhibit two-step degradation only under air.
Co-reporter:Feng Gao, Lifang Tong, Zhengping Fang
Polymer Degradation and Stability 2006 Volume 91(Issue 6) pp:1295-1299
Publication Date(Web):June 2006
DOI:10.1016/j.polymdegradstab.2005.08.013
A novel phosphorus–nitrogen containing intumescent flame retardant (P–N IFR) was prepared via the reaction of a caged bicyclic phosphorus (PEPA) compound and 4,4′-diamino diphenyl methane (DDM) in two steps. The product was added to poly(butylene terephthalate) (PBT) to obtain halogen-free flame retarded polyester. UL-94 test, thermogravimetry and in situ infrared spectroscopy were used to characterize the flammability, thermal degradation properties and the char-forming process. It was shown that the phosphorus–nitrogen containing compound could improve both the flame retardancy and thermal stability more effectively than other P–N flame retardants. Furthermore, it was a good char-forming agent incorporated with the co-addition of polyurethane (PU) when the combustion occurred. The formation of P–N structure was incorporated in the char layer.
Co-reporter:Juan Li, Zhengping Fang, Lifang Tong, Aijuan Gu, Fu Liu
European Polymer Journal 2006 Volume 42(Issue 12) pp:3230-3235
Publication Date(Web):December 2006
DOI:10.1016/j.eurpolymj.2006.08.018
The non-isothermal crystallization behaviors of multi-walled carbon nanotubes (MWNTs)/polyamide 6 (PA6) composites were investigated by differential scanning calorimetry (DSC). Three methods, namely, Avrami, Ozawa and Mo, were carried out to analyze the non-isothermal crystallization data. The results showed that the MWNTs in PA6 acted as effective nucleation agents. However the crystallization rate of composites obtained was lower than that of the neat PA6. It is indicated that the presence of MWNTs influenced the mechanism of nucleation and the growth of PA6 crystallites.
Co-reporter:Jianguo Wang;Aijuan Gu;Fu Liu;Lihua Xu
Journal of Applied Polymer Science 2006 Volume 100(Issue 1) pp:97-104
Publication Date(Web):9 JAN 2006
DOI:10.1002/app.22647
Amino-functionalization of multiwalled carbon nanotubes (MWCNTs) was carried out by grafting triethylenetetramine (TETA) on the surfaces of MWCNTs through the acid–thionyl chloride way. The amino-functionalized MWCNTs show improved compatibility with epoxy resin and, as a result, more homogenous dispersion in the matrix. The mechanical, optical, and thermal properties of the amino-functionalized MWCNT/epoxy composites were also investigated. It was found that introducing the amino-functionalized MWCNTs into epoxy resin greatly increased the charpy impact strength, glass transition temperature, and initial decomposing temperature of cured epoxy resin. In addition, introducing unfunctionalized MWCNTs into epoxy resin was found greatly depressing the light transmission properties, which would affirmatively confine the application of the MWCNTs/epoxy composites in the future, while much higher light transmittance than that of unfunctionalized MWCNTs/epoxy composites was found for amino-functionalized MWCNTs/epoxy composites. SEM of the impact cross section and TEM of ultrathin film of the amino-functionalized MWCNTs/epoxy composites showed that the amino-functionalized MWCNTs were wetted well by epoxy matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 97–104, 2006
Co-reporter:Zhengping Fang;Yuzhen Xu;Lifang Tong
Journal of Applied Polymer Science 2006 Volume 102(Issue 3) pp:2463-2469
Publication Date(Web):23 AUG 2006
DOI:10.1002/app.24569
Two type of nanocomposites—an immiscible blend, high density polyethylene/polyamide 6 (HDPE/PA-6) with organomodified clay, and a compatibilized blend, high density polyethylene grafted with acrylic acid/PA-6 (PEAA/PA-6) with organomodified clay—were prepared via melt compounding. X-ray diffraction and transmission electron microscopy results revealed that the clay was intercalated and partially exfoliated. Positron annihilation lifetime spectroscopy has been utilized to investigate the free-volume hole properties of two type of nanocomposites. The results show a negative deviation of free-volume size in PEAA/PA-6 blend, and a positive deviation in HDPE/PA-6 blend, and I3 has a greater negative deviation in compatibilized blend than in immiscible blend due to interaction between dissimilar chains. For nanocomposites based on polymer blends, in immiscible HDPE/PA-6/organomodified clay system, the variation of free-volume size with clay content is not obvious and the free-volume concentration and fraction decreased. While in the case of compatibilized PEAA/PA-6/organomodified clay nanocomposites, complicated variation of free-volume properties due to interactions between two phases and organomodified clay was observed. And the interaction parameter β shows the interactions between polymers and organomodified clay. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2463–2469, 2006
Co-reporter:Jianguo Wang;Aijuan Gu
Polymer Engineering & Science 2006 Volume 46(Issue 5) pp:635-642
Publication Date(Web):31 MAR 2006
DOI:10.1002/pen.20512
Two types of multi-walled carbon nanotubes (MWCNTs), chemically modified and unmodified, were dispersed in epoxy resin with ultrasonication. The light transmittance characteristics of epoxy composites with different ratios of MWCNTs to epoxy resin were measured at wavelengths ranging from 200 to 1100 nm. Results showed that composites with modified MWCNTs had a much higher light transmittance than those with unmodified MWCNTs. This was presumably due to a more uniform dispersion of modified MWCNTs in the epoxy matrix, as indicated by both transmission electron microscopy and optic microscopy. The wavelength dependency of light transmittance of the composites was expressed empirically as a function of weight fraction (fw) of MWCNTs and the light wavelength (λ). POLYM. ENG. SCI. 46:635–642, 2006. © 2006 Society of Plastics Engineers.
Co-reporter:Zhengping Fang;Jianguo Wang;Aijuan Gu
Polymer Engineering & Science 2006 Volume 46(Issue 5) pp:670-679
Publication Date(Web):31 MAR 2006
DOI:10.1002/pen.20487
Two types of multiwalled carbon nanotubes (MW-CNTs) with different structure and morphology were used to fabricate cyanate ester (CE) matrix composites. Mechanical, thermal, and transmission electron microscopy tests were performed to evaluate the different effects of the two types of MW-CNTs on the structure and properties of MW-CNT/CE composites. Results showed that the bundled MW-CNTs were easier to be dispersed in CE matrix than single MW-CNTs, and could improve the toughness and stiffness of CE material more significantly. Functionalization of the two types of MW-CNTs, which was achieved by grafting triethylenetetramine groups onto the surface of MW-CNTs, was helpful in improving the dispersion of the MW-CNTs in CE, and thus in fabricating MW-CNT/CE composites with improved mechanical and thermal properties. POLYM. ENG. SCI. 46:670–679, 2006. © 2006 Society of Plastics Engineers
Co-reporter:Zhenghong Guo;Lifang Tong
Polymer International 2005 Volume 54(Issue 12) pp:
Publication Date(Web):5 OCT 2005
DOI:10.1002/pi.1896
Blends of polystyrene (PS) with polyolefin elastomer (POE) were prepared by a reactive extrusion method. In order to increase the compatibility of the two blending components, a Lewis acid catalyst, aluminium chloride (AlCl3), was adopted to initiate the Friedel–Crafts alkylation reaction. Fourier-transform infrared (FTIR) spectra of the PS/POE/AlCl3 blends extracted with butanone verified the graft structure between the PS and POE. Because the in situ generated PS-graft-POE copolymers acted as compatibilizers, the mechanical properties of PS/POE blends were greatly improved. For example, after compatibilization, the Charpy impact strength of an 80/20 (wt%) PS/POE blend was increased from 6.29 to 8.50 kJ m−2. Scanning electron microscopy (SEM) showed that the size of the droplets decreased from 9–10 µm to less than 2 µm with the addition of AlCl3. Gel permeation chromatography (GPC) showed competition between the grafting reaction and the degradation of blending components in the presence of AlCl3. Copyright © 2005 Society of Chemical Industry
Co-reporter:Yu Feng;Wei Mao;Aijuan Gu
Journal of Applied Polymer Science 2005 Volume 96(Issue 3) pp:632-637
Publication Date(Web):23 FEB 2005
DOI:10.1002/app.21470
Cyanate ester (CE)/bentonite (BT) nanocomposites were prepared by melt blending of CE with NH4+-BT. The nanostructure of CE/BT nanocomposites was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that partially intercalated and partially exfoliated structures coexisted in CE/BT nanocomposites containing 2.5 wt % BT with respect to that of bulk CE. Below 2.5 wt % BT content, a totally exfoliated and disordered structure was formed in the nanocomposites. The exfoliated BT enhanced the toughness of CE/BT nanocomposites. The impact strength showed a maximum of 7.1kJ/m2 at 1 wt % BT, compared to 3.8kJ/m2 of pure CE. Furthermore, results of thermogravimetric analysis (TGA) suggest that CE/BT nanocomposites have higher thermal stability. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 632–637, 2005
Co-reporter:Zhengping Fang;Lifang Tong;Yuzhen Xu
Journal of Applied Polymer Science 2005 Volume 96(Issue 6) pp:2429-2434
Publication Date(Web):14 APR 2005
DOI:10.1002/app.21708
Acrylic acid (AA) grafted high-density polyethylene (HDPE)/bentonite (BT) composites and HDPE/BT composites were prepared via melt compounding. XRD and TEM results indicated that the modification of AA grafting promoted the dispersion and intercalation of BT in HDPE matrix; IR proved that there were interactions between AA and BT sheets. Consequently, with increasing BT content, the tensile strength and Young's modulus of HDPE-g-AA/BT nanocomposites increased, while that of HDPE/BT composites decreased. Moreover, the addition of BT to HDPE-g-AA decreased the ability of crystallization of the matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2429–2434, 2005
Co-reporter:Yu Feng;Aijuan Gu
Polymer International 2005 Volume 54(Issue 2) pp:
Publication Date(Web):1 DEC 2004
DOI:10.1002/pi.1693
Carboxyl-terminated butadiene-acrylonitrile rubber (CTBN) has often been used to improve the toughness of cyanate ester (CE) resin while sacrificing modulus and thermostability. In this paper, the addition of the appropriate amount of epoxy resin (EP) to the CE/CTBN system is shown to not only increase the modulus and thermostability of the blend, but also improve the toughness. The values of impact strength showed a maximum for the CE/CTBN/EP 100/5/5 blend. The temperature of 10 % weight loss (T10) improves from 376 °C for CE/CTBN 100/5 to 407 °C for the CE/CTBN/EP 100/5/2.5 blend. It is proposed that addition of the appropriate amount of EP can decrease the mobility and increase the stability of CTBN via the reaction between the terminal carboxyl group of CTBN and the hydroxyl group of EP. But a very high EP concentration will decrease the crosslinking density of CE, consequently reducing the mechanical properties and thermostability of the blends. Copyright © 2004 Society of Chemical Industry
Co-reporter:Zhengping Fang;Zhenghong Guo;Linlin Zha
Macromolecular Materials and Engineering 2004 Volume 289(Issue 8) pp:743-748
Publication Date(Web):2 AUG 2004
DOI:10.1002/mame.200300356
Summary: Polystyrene (PS) was toughened with ethylene-propylene-diene terpolymer (EPDM) in the presence of styrene-butadiene-styrene block copolymer (SBS). Incorporation of SBS into the PS/EPDM blends clearly improved the impact properties. For PS/EPDM/SBS (mass ratio: 69/21/10) blends, the notched Charpy impact strength reached a maximum value of 26.3 kJ/m2. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that SBS was distributed on the interface between PS and EPDM. Butanone extraction and FTIR analysis found that there was a grafting reaction between PS and EPDM phase during melt compounding. Shearing and processing rheological behaviors of blends were evaluated with a Haake capillary rheometer and a torque rheometer, respectively.
Co-reporter:Zhengping Fang;Aijuan Gu;Yu Feng
Polymers for Advanced Technologies 2004 Volume 15(Issue 10) pp:628-631
Publication Date(Web):11 OCT 2004
DOI:10.1002/pat.519
The carboxyl terminated butadiene-acrylonitrile (CTBN) rubber was used to improve the toughness of the cyanate ester (CE) resin. The toughness of the modified blends depended on the CTBN content. The addition of 10 phr (g/100gCE) CTBN in CE resin led to a 200% increase in the impact strength with a loss of storage modulus. The transmission electron microscopy result showed the existence of rubber particles, inferring that phase separation had occured after curing. The thermogravimetric analysis curve of CTBN indicated the presence of cavities which also can be observed on the fractured surface in the scanning electron microscopy pictures using high magnification. Thus, phase-separation and cavities toughening mechanisms function together to improve the toughness. Copyright © 2004 John Wiley & Sons, Ltd.
Co-reporter:Yan Liu, Yan Zhang, Zhenhu Cao, Zhengping Fang
Fire Safety Journal (October 2013) Volume 61() pp:185-192
Publication Date(Web):1 October 2013
DOI:10.1016/j.firesaf.2013.09.009
•Three novel intumescent flame retardants (IFRs) were synthesized and characterized.•The results from UL-94 showed that EVA/IFRs blends all could reach V-2 rating.•The PHRR value is reduced by 31% and the LOI value increased from 19 to 24.Three novel intumescent flame retardants (IFRs) containing phosphorus and nitrogen based on Schiff bases, poly(phosphonate ester(s)) (designated as PAB, PEB, and PPB), were synthesized and characterized. Thermal stability and flammability properties of ethylene-vinyl acetate copolymer (EVA)/30% IFRs blends were investigated by thermogravimetric analysis (TGA), limited oxygen index (LOI), vertical burning test (UL-94) and microscale combustion calorimetry (MCC). The results from UL-94 showed that EVA/IFRs blends all could reach V-2 rating. The addition of PAB into EVA reduced the PHRR value by 31%, and the LOI value increased from 19 to 24. Scanning electron microscope (SEM) observation results indicated that the existence of the cohesive charred layer on the surface of the residue was responsible for the improvement of the flame retardancy of EVA.
Co-reporter:Baoxian Du, Zhenghong Guo, Ping'an Song, Hui Liu, Zhengping Fang, Yu Wu
Applied Clay Science (July 2009) Volume 45(Issue 3) pp:178-184
Publication Date(Web):July 2009
DOI:10.1016/j.clay.2009.05.003
Co-reporter:Yan Zhang, Xiaonan Li, Zhengping Fang, T. Richard Hull, Antonios Kelarakis, Anna A. Stec
Polymer Degradation and Stability (February 2017) Volume 136() pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.polymdegradstab.2016.12.018
The effects of cobalt acetate (CoAc), manganese acetate (MnAc), nickel acetate (NiAc) and zinc acetate (ZnAc) as fire retardant additive in intumescent polypropylene (PP) formulations containing PP/ammonium polyphosphate (APP)/pentaerythritol (PER) are reported. The limiting oxygen index (LOI) and vertical burning (UL94) tests and cone calorimetry were used to quantify the enhancement. Environmental chamber rheometry, thermal gravimetric analysis and the morphology of the residual char were used to investigate the mechanism of enhancement. The incorporation of small quantities of metal acetates had a significant influence on the fire behaviour. As an example, 0.7 wt% MnAc improved the UL 94 rating of PP/APP + PER (mass ratio 100/25, with APP/PER = 3/1) sample from V-2 to V-0, while 1 wt% MnAc reduced the peak heat release rate and the total heat release by 18% and 12% in the cone calorimeter. Rheological data, cone calorimetry, and photographs of the residual char showed how the fire retardancy of the systems were affected by the melt viscosity, which depended on the loading of metal acetate. During thermal decomposition, the metal acetates promote the crosslinking of the polymer and the fire retardant, reinforcing the protective intumescent layer. While, the effect is most potent at the optimal metal loadings. At higher MnAc loadings, the benefit of a stronger char is overwhelmed by the adverse effect of crosslinking on the transition char layer. Thus, this paper offers a new insight into the mechanism of the intumescent fire retarded PP system.
Co-reporter:Haiyun Ma, Lifang Tong, Zhongbin Xu, Zhengping Fang
Applied Clay Science (December 2008) Volume 42(Issues 1–2) pp:238-245
Publication Date(Web):December 2008
DOI:10.1016/j.clay.2007.12.009
Co-reporter:Shiya Ran, Zhenghong Guo, Chao Chen, Liping Zhao and Zhengping Fang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 9) pp:NaN3007-3007
Publication Date(Web):2013/11/29
DOI:10.1039/C3TA14179A
Multiwalled carbon nanotube (MWNT) bridged cerium phenylphosphonate (CeHPP) hybrids (Ce-MWNTs) were facilely prepared through the in situ introduction of MWNTs into the hydrothermal reaction system of CeHPP, aiming at enhancing the flame retardancy of the polymer. Morphological observations indicated that the MWNTs acted as bridges to connect CeHPP lamellas to form a consecutive structure. Moreover, due to the good dispersion of CeHPP and the acting force between CeHPP and the MWNTs, the hybrids were dispersed uniformly resisting the strong intermolecular attractions. The hybrids led to a reduction in the peak heat release rate (PHRR) of the conventional flame retardant high-density polyethylene (HDPE) composite and improved the UL-94 grade from V-2 to V-0, indicating that they could confer a better flame retardancy on HDPE compared to the CeHPP or MWNTs alone. The results of the pyrolysis products and the morphology of the chars gave the evidence that Ce-MWNTs could enhance the physical barrier effect to retard the vaporization of flammable gases and the transfer of heat because of the mutual complementarity of the CeHPP and MWNTs.
Co-reporter:Pingan Song, Liping Zhao, Zhenhu Cao and Zhengping Fang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 21) pp:NaN7788-7788
Publication Date(Web):2011/04/08
DOI:10.1039/C1JM10395D
In the present study, the effects of covalently functionalized carbon nanotubes (CNTs) decorated with C60 (abbr. C60-d-CNT) on thermal, flame retardancy and mechanical properties of polypropylene (PP) are investigated. Compared with pristine CNTs, the C60-d-CNT is more easily dispersed in the PP matrix through reactive compatibilization. With the incorporation of C60-d-CNT, thermal oxidation degradation of PP is considerably delayed. Compared to PP, at 1.0 wt% loading of C60-d-CNT, the initial degradation temperature (T5) and maximum weight loss temperature (Tmax) in air are enhanced by 68 °C and 87 °C, respectively. Furthermore, incorporating 1.0 wt% C60-d-CNT can remarkably reduce the peak heat release rate (PHRR) by 71% relative to that of PP, and slow down the combustion process to some extent. The free-radical trapping effect of C60 and the CNTs network are responsible for the improved thermal and flame retardancy properties. Meanwhile, addition of C60-d-CNT also causes enhanced mechanical properties of PP nanocomposites to a certain degree.
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