Co-reporter:Jing Liu, Yu Ma, Rongliang Wu, Muhuo Yu
Polymer 2016 Volume 97() pp:335-345
Publication Date(Web):5 August 2016
DOI:10.1016/j.polymer.2016.05.050
•Stepwise polymerization kinetics was studied by a new molecular simulation algorithm.•Scaling of polymerization kinetics in diffusion-controlled regime was proposed.•Transition from reaction-to diffusion-controlled kinetics was provided.The kinetics of stepwise polymerization in the diffusion-controlled regime was investigated using dynamic Monte Carlo simulation and scaling analysis. In analogy to Flory’s expression, a concise expression of reaction kinetics in diffusion controlled regime was proposed, where the number average degree of polymerization was related to the initial concentration and reaction time through a power law dependence. In addition, the transition of kinetics from the classical reaction-controlled to diffusion-controlled regime was predicted and examined via simulation. The results provided a good description of kinetics for the late stage of stepwise polymerizations, and demonstrated good agreements with the various experiments.
Co-reporter:Kong Haijuan, Yang Peng, Teng Cuiqing and Yu Muhuo
RSC Advances 2015 vol. 5(Issue 72) pp:58916-58920
Publication Date(Web):08 Jun 2015
DOI:10.1039/C5RA07919E
A process of surface modification of poly(p-phenylene terephthalamide) fibers was reported to improve the adhesion to epoxy, in which the fibers were treated in supercritical carbon dioxide (ScCO2) with hexamethylene diisocyanate (HDI). After the modification, the surface chemical composition of the fibers was identified using X-ray photoelectron spectroscopy (XPS), and the results showed Ph-NH2 groups are formed on fibers after treatment in ScCO2 with HDI. From the scanning electron microscope (SEM) and atomic force microscope (AFM) results, we can find the surface of fibers treated with HDI in ScCO2 became much rougher. The interfacial properties of aramid/epoxy composites were investigated by microdebond test, the results showed that the interfacial shear strength (IFSS) was improved by 22%. It is beneficial for the application of the fiber material as reinforcement in an epoxy system that can improve the interfacial property of PPTA fibers with epoxy.
Co-reporter:Shuping Liu, Keqing Han, Lei Chen, Ying Zheng and Muhuo Yu
RSC Advances 2015 vol. 5(Issue 47) pp:37669-37674
Publication Date(Web):24 Apr 2015
DOI:10.1039/C5RA00476D
A new method of melt-spun process was developed to prepare PAN precursor fibers using ionic liquid as the medium of processing. Melt-spun precursor fibers exhibited a partially cyclized structure. For the different structure of melt-spun precursor fibers from solution-spun precursor fibers, it is necessary to investigate the oxidation process of the melt-spun precursors. In this paper, the influence of air circulation on the structure and properties of melt-spun precursor fibers during the oxidative process was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry, etc.Results showed that the air circulation almost had no visible effects on the chemical structure of pre-oxidized fibers. The crystallinity and the crystal size of pre-oxidized melt-spun fibers increased with the increase of air circulation. When the air circulation was 6 L min−1, the pre-oxidized melt-spun fibers had the maximum density and tensile strength. Meanwhile, the tensile strength of the final carbon fibers reached a maximum.
Co-reporter:Shuping Liu;Keqing Han;Lei Chen;Ying Zheng
Polymer Engineering & Science 2015 Volume 55( Issue 12) pp:2722-2728
Publication Date(Web):
DOI:10.1002/pen.24121
Carbon fiber has many excellent properties. Currently, the precursor fiber of polyacrylonitrile (PAN)-based carbon fiber is made from solution by wet or dry spinning process that requires expensive solvents and costly solvent recovery. To solve this problem, we developed a melt-spun process with ionic liquid as the medium of processing. The melt-spun precursor fiber exhibited partially cyclized structure. The structure and properties of the melt-spun PAN precursor fiber were analyzed by combination of scanning electron microscope, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, thermogravimetry, ultraviolet spectroscopy, flotation technique, sound velocity orientation test, linear density, and tensile strength tests. The results showed that the tensile strength of melt-spun PAN precursor fiber was fairly high reached up to 7.0 cN/dtex. The reason was the low imperfect morphology and a cyclized structure formed by in situ chemical reaction during melt-spun process. Due to the existence of partially cyclized structure in the melt-spun PAN precursor fiber, exothermic process was mitigated and the heat evolved decreased during thermal stabilization stage in comparison with commercial precursor fibers produced by solution-spun, which could shorten the residence time of thermal stabilization and reduce the cost of final carbon fiber. POLYM. ENG. SCI., 55:2722–2728, 2015. © 2015 Society of Plastics Engineers
Co-reporter:Yue Zhang, Haifeng Li, Xinda Li, Magdi E. Gibril, Muhuo Yu
Carbohydrate Polymers 2014 Volume 99() pp:126-131
Publication Date(Web):2 January 2014
DOI:10.1016/j.carbpol.2013.07.084
•A new processing technology “in situ reactive extrusion” of cellulose was applied.•In situ formation of side chain on cellulose destroyed the hydrogen bond network.•The in situ derivatization effect of cellulose with anhydride group was better.•The solubility of modified cellulose with maleic anhydride in IL was raised to 25%.•The short extrusion time and little IL restrained the degradation of cellulose.In order to prepare the spinning solution of cellulose with high concentration in environmentally friendly solvent, cellulose was chemically modified by in situ reactive extrusion with several chemicals, such as urea, phthalic anhydride (PA), maleic anhydride (MA) and butyl glycidyl ether (BGE) and with ionic liquid namely 1-N-butyl-3-methylimidazolium chloride (BMIMCl) as reaction medium. These four modifiers all in situ grafted onto cellulose and the modification effectiveness was found to decrease in the sequence, MA > PA > BGE > urea. The formation of side chain on cellulose backbone destroyed the regularity of cellulose chains and the hydrogen bond network efficiently. The concentration of modified cellulose in spinning solution can be up to 14–25%, comparing with 9% for unmodified cellulose in BMIMCl. The high solid content results in high efficiency and less energy consumption of fiber production and solvent recycle.
Co-reporter:Yue Zhang, Xinda Li, Yanping Yang, Ai Lan, Xiaoyun He and Muhuo Yu
RSC Advances 2014 vol. 4(Issue 65) pp:34584-34590
Publication Date(Web):06 Aug 2014
DOI:10.1039/C4RA02727B
In order to prepare bio-degradable cellulose-based fibers in an environmentally-friendly way, graft copolymerization of L-lactide (LLA) onto cellulose was carried out through a co-rotating twin-screw extruder and then the blend melt was directly spun. Ionic liquid, namely 1-allyl-3-methylimidazolium chloride ([AMIM]Cl), was used as the reaction medium and tin(II) octoate was used as a catalyst. The graft copolymerization effect was evaluated by the study of FTIR, 13C-NMR, WAXD, TGA and SEM. The results indicated that LLA successfully in situ grafted onto the cellulose backbone and PLA long-chain branches were formed, which restrained the thermal and photo degradation of regenerated cellulose and hindered the crystallization of cellulose. The morphology of the cellulose-graft-polylactide blend fiber showed a smooth surface and ductile cross section due to the destruction of the hydrogen bond network of cellulose and the better thermoplastic properties of the PLA branches. Because cellulose-g-PLA blend with 1000 g LLA prepared at 50 rpm rotation speed has good spinnability, drawability and thermostability, the mechanical properties of this fiber were better than other cellulose-g-PLA blend fibers. Compared to other commercial cellulose fibers, the in situ graft copolymerization modification of cellulose with LLA resulted in better mechanical properties of cellulose-based fibers, high efficiency of cellulose fiber production and less energy consumption in solvent recycling.
Co-reporter:Shuang Li;Keqing Han;Huaiping Rong;Xuanzhe Li
Journal of Applied Polymer Science 2014 Volume 131( Issue 10) pp:
Publication Date(Web):
DOI:10.1002/app.40250
ABSTRACT
In this article, aramid fibers III were surface modified using an ammonia-plasma treatment to improve the adhesive performance and surface wettability. The surface properties of fibers before and after plasma treatment were investigated by X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, and water contact angle measurements. The interfacial shear strength of each aramid fibers III-reinforced epoxy composites was studied by micro-debonding test. The ammonia-plasma treatment caused the significant chemical changes of aramid fibers III, introducing nitrogen-containing polar functional groups, such as CN and CONH, and improving their surface roughness, which contributed to the improvement of adhesive performance and surface wettability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40250.
Co-reporter:Dawelbeit Ahmed;Hongpeng Zhong;Haijuan Kong;Jing Liu;Yu Ma
Fibers and Polymers 2014 Volume 15( Issue 9) pp:1850-1854
Publication Date(Web):2014 September
DOI:10.1007/s12221-014-1850-z
Poly(p-phenylene terephthalamide) fibers prepared by dry-jet wet spinning processes have a notable response to very brief heat treatment (seconds) under tension. The modulus of the as-spun fiber can be greatly affected by the heat treatment conditions (temperature, tension and duration). The crystallite orientation and the fiber modulus will increase by this short-term heating under tension. The present research reports the heat treatment techniques, devices and its process conditions. It reports in details the structural relationships between the fiber properties which are influenced by the heat treatment process. In particular, focuses deeply on the effect of the crystal orientation changes of the fibers, on the mechanical properties and, also, investigates the thermal degradation steps & behaviours of the heat treated fibers. The heat treated PPTA fibers have a molecular orientation higher than that for the as-spun one.
Co-reporter:Xiaoling Feng, Sen Zhang, Shu Zhu, Keqing Han, Mingli Jiao, Jian Song, Yu Ma and Muhuo Yu
RSC Advances 2013 vol. 3(Issue 29) pp:11738-11744
Publication Date(Web):29 Apr 2013
DOI:10.1039/C3RA40899J
In this paper, we report a novel and facile method of pressure-induced-flow (PIF) processing that remarkably enhanced the mechanical properties of polylactic acid (PLLA)–PEG blends. The impact strength and bending strength increased by about 20 and 4 times, respectively. Meanwhile, the tensile strength and elongation at break were 3 and 7 times higher compared with raw samples. As indicated by DSC and polarizing microscopy, POM, oriented spherulites were present in the sample after PIF processing. The SEM results showed that the fracture surface of the PIF samples became oriented and much rougher. The cell culture results indicated that the PLLA–PEG blends after PIF processing still maintain as good biocompatibility as the original.
Co-reporter:Yue Zhang, Xinda Li, Haifeng Li, Magdi E. Gibril, Keqing Han and Muhuo Yu
RSC Advances 2013 vol. 3(Issue 29) pp:11732-11737
Publication Date(Web):07 May 2013
DOI:10.1039/C3RA41236A
In order to prepare a cellulose-based water absorbent material in an environmentally-friendly way, a cellulose-graft-polyacrylamide (cellulose-g-PAM) copolymer is synthesized by in situ graft copolymerization through a co-rotating twin-screw extruder. An ionic liquid, namely 1-N-butyl-3-methylimidazolium chloride, is used as the reaction medium and ceric ammonium nitrate is used as the initiator. The graft copolymerization effect is evaluated by the study of the thermal and rheological properties of the copolymers. FTIR and elemental analysis results show that the amide groups of PAM successfully graft onto the cellulose backbone and the graft ratio of the cellulose-g-PAM is increased with the increase in AM content. Thermal analysis shows that the thermal stability of cellulose-g-PAM and the glass transition temperature of PAM are increased as the graft ratio increases due to the formation of PAM long-chain branches which disturb the segment motion of the cellulose chains. In comparison with cellulose, the dehydration peak of cellulose-g-PAM displays a larger endothermic enthalpy and shifts to higher temperature. Rheological results show that the storage modulus curve of cellulose-g-PAM with a high graft ratio exhibits a plateau at low frequency and the tan δ curve displays a peak value, indicating that the large amount of PAM branches cause the entanglement of copolymer chains and improve the toughness of the copolymers.
Co-reporter:Sen Zhang, Shu Zhu, Xiaoling Feng, Keqing Han, Qian Huan, Jian Song, Yu Ma and Muhuo Yu
RSC Advances 2013 vol. 3(Issue 19) pp:6879-6887
Publication Date(Web):31 Jan 2013
DOI:10.1039/C3RA22515A
In this paper, firstly, we systematically explain the deformation mechanism of the high impact polystyrene (HIPS) via pressure-induced-flow (PIF) processing. As indicated by TEM, AFM and SAXS, we find that a single salami domain is intensively deformed into a disk-like shape, and rubber-disk domains form parallel and oriented structure. In addition, chains in the interphase are oriented and become stiffer as suggested by FTIR and DMA. Such structural variation gives rise to the improvement in both strength and toughness. Impact and tensile strength for high impact polystyrene (HIPS) with parallel and oriented structure increase by 100% and 30% respectively. Moreover, we studied the toughening mechanism. The post-impact fracture surface transits from normal smooth fish scale like morphology to aligned grooves with high roughness, as demonstrated by SEM. The craze of impact fracture surface of HIPS samples after PIF processing is characterized by TEM. Finally, a model for the confinement of crazing is proposed.
Co-reporter:Magdi E. Gibril, Li Huan, Li haiFeng, Li Xin Da, Zhang Yue, Keqing Han and Yu Muhuo
RSC Advances 2013 vol. 3(Issue 4) pp:1021-1024
Publication Date(Web):21 Nov 2012
DOI:10.1039/C2RA22296E
A facile method was adopted to perform succinylation of cellulose using succinic anhydride and a reactive extrusion process in the presence of ionic liquid (IL), 1-butyl-3-methylimidazolium chloride [Bmim]Cl. Succinylated cellulose with a degree of substitution (DS) in the range of 0.166–0.245 was obtained. Upon characterization, the existence of succinylation between cellulose and succinic anhydride was confirmed.
Co-reporter:Yincai Tian, Keqing Han, Wenhui Zhang, Jingjie Zhang, Huaiping Rong, Dan Wang, Bin Yan, Shuping Liu, Muhuo Yu
Materials Letters 2013 Volume 92() pp:119-121
Publication Date(Web):1 February 2013
DOI:10.1016/j.matlet.2012.10.042
Carbon fibers have excellent properties; however, their wide application is limited by the high cost. In the production process of carbon fibers, the stabilization is the most time-consuming step. If the heat emission can be reduced or its distribution widened, it will be helpful to improve the speed of the stabilization process. In the previous article, we have reported the effect of temperature on the structure of polyacrylonitrile (PAN) in ionic liquids. In this work, influence of residence time on the structures of PAN in ionic liquids is studied by a twin-screw extruder. The formation of C=C and C=N groups was indicated by Fourier transform infrared spectroscopy (FTIR) and Ultraviolet Visible (UV–vis) absorption spectra, which was attributed to the occurrence of cyclization and dehydrogenation during the extruding process. The cyclization degree was calculated by differential scanning calorimetry (DSC) test, which can be up to 29.4% with the residence time of 40 min at 210 °C. Therefore, this method can be helpful to improve the production efficiency in the subsequent stabilization process by widening and reducing the distribution of heat emission in the product process of PAN fibers.Highlights► Effect of residence time on the structure of PAN was investigated by using a twin-screw extruder. ► Formation of C=C and C=N groups was illustrated by using FTIR and UV–vis tests. ► Degree of cyclization is up to 29.4% with the residence time of 40 min at 210 °C.
Co-reporter:Yue Zhang;Haifeng Li;Xinda Li;Magdi E. Gibril;Keqing Han
Journal of Polymer Research 2013 Volume 20( Issue 6) pp:
Publication Date(Web):2013 June
DOI:10.1007/s10965-013-0171-z
With ionic liquid namely 1-N-butyl-3-methylimidazolium chloride ([BMIM]Cl) as reaction medium in cellulose modification, maleic anhydride/glycidyl methacrylate-grafted ethylene-octene copolymer (POE-g-(MA/GMA)) was blended with cellulose by a co-rotating twin-screw extruder. Cellulose/POE-g-(MA/GMA) blend was examined by FTIR, 13C-NMR, WAXD, DSC, TGA, rheology and tensile properties. Owing to the reaction between functional groups of POE-g-(MA/GMA) and hydroxyl groups of cellulose and the high mobility of POE-g-(MA/GMA), hydrogen bond network in cellulose was destructed and cellulose-b-POE-g-(MA/GMA) copolymer was synthesized in-situ. As a result, the reduction in intermolecular force of cellulose improved the melt flowability and spinnability of cellulose blend. The formation of long-chain branches hindered the crystallization and increased the thermal stability of cellulose on one hand and obtained much more chemical bond fracture under stress action and increased the tensile strength and elongation at break of the blend fibers on the other. However, the addition of 15 wt% POE-g-(MA/GMA) led to the formation of crosslined structure, so a high degree of chain entanglement increased the dynamic viscosity and decreased the spinnability of cellulose/POE-g-(MA/GMA) blend.
Co-reporter:Qian Huan, Shu Zhu, Yu Ma, Juanjuan Zhang, Sen Zhang, Xiaolin Feng, Keqing Han, Muhuo Yu
Polymer 2013 Volume 54(Issue 3) pp:1177-1183
Publication Date(Web):5 February 2013
DOI:10.1016/j.polymer.2012.12.055
Mechanical property of semicrystalline polymer with large-size spherulites is rather poor, and needs to be improved by adding nucleating agent to make spherulites smaller. However, the nucleating agent causes many problems limiting its applications. In this paper, we report a method to simultaneously improve the toughness and tensile strength of isotactic polypropylene (iPP) with large-size spherulites by deformation of spherulites and orientation of lamellaes through pressure-induced flow processing (PIF-processing) at solid state. The initial spherulite sizes of iPP samples with the same crystallinity and crystal form were controlled by adding nucleating agent (NA, Talc, nano-scaled), and then the samples were subjected to PIF-processing. The resulting mechanical performance of the bulk materials, including impact and tensile strength, was simultaneously enhanced. In particular, the impact strength increases upto 8 folds higher than those obtained by conventional processing for the same bulk materials, attributing to the synergistic effect of both the orientation and the large-size spherulites. The measurements of SEM, XRD and SAXS revealed the spherulites deformation and lamellae orientation during PIF-processing, as the basis of discussing the mechanism.
Co-reporter:Sen Zhang, Shu Zhu, Keqing Han, Xiaoling Feng, Yu Ma, Muhuo Yu, Günter Reiter
Polymer 2013 Volume 54(Issue 21) pp:6019-6025
Publication Date(Web):4 October 2013
DOI:10.1016/j.polymer.2013.08.025
We demonstrate that without changing the filler content mechanical properties of commodity plastics with immiscible soft inclusions can be decisively enhanced, simply by pressure induced flow processing in the solid state. As an example, we have chosen acrylonitrile-butadiene-styrene (ABS), where shape and orientation of the soft fillers were changed by processing, resulting in an array of aligned and oriented nanosize deformed rubber domains. These deformed domains effectively controlled the propagation of cracks inside the solid matrix and were responsible for a multifold increase of tensile and impact toughness. Thus, appropriate processing allows manufacturing plastics with high impact resistance in accordance with engineering needs.
Co-reporter:Musa E. Babiker;Yu Muhuo
Arabian Journal for Science and Engineering 2013 Volume 38( Issue 3) pp:479-490
Publication Date(Web):2013 March
DOI:10.1007/s13369-012-0371-6
In this paper the effects of loading of montmorillonite (MMT) on the properties of ultra-high molecular weight polyethylene/montmorillonite (UHMWPE/MMT) nano-composites were reported. The UHMWPE gel sheet with nanoparticles of MMT clay was prepared by using paraffin oil as a non-volatile solvent. The paraffin oil was removed using two steps, i.e., mini-mold as PIF and extraction processes. The microstructure of the gel sheet shows good dispersion of MMT clay nanoparticles and hence intercalation and exfoliation between the layers of the microstructure gel sheet, i.e., MMT clay onto the layer surface by means of gel and PIF processes in the microstructure gel sheet shows that the layer spacing was increased significantly or even exfoliated. For intercalated nanocomposites, different layer spacing corresponds to different chain flexibility and the presence of multi-peaks is caused by the processing of these materials. The resulting exfoliated UHMWPE/organo-MMT nanocomposites were characterized by transmission electron microscopy and scanning electron microscope. The thermal properties of the nanocomposites were investigated by thermogravimetric analysis, dynamic mechanical analysis and differential scanning calorimetry. The results obtained provide a guide to the interfacial design of organic/inorganic materials.
Co-reporter:Hong Xu;Cuiqing Teng;Zhiping Mao
Journal of Polymer Research 2012 Volume 19( Issue 9) pp:
Publication Date(Web):2012 September
DOI:10.1007/s10965-012-9960-z
A new process to prepare L-lactic acid based polymer with high molecular-weight was established. In this process, the carboxyl terminated poly (L-lactic acid) (PLLA) prepolymer was first synthesized via polycondensation of L-lactic acid and a little adipic acid, and then the molecular weight of PLLA was increased by a chain-extending reaction using bisphenol-A epoxy resin as a chain extender. In situ FTIR was used to characterize the activity of reaction between epoxy groups at the end of bisphenol-A epoxy resin and carboxyl groups at the end of PLLA prepolymer, and the results showed that the reaction was of high activity. The weight-average molecular weight of prepared L-lactic acid based copolymer (PLLA-co-BisA ER) was up to 210,000 at an optimum synthetic condition. The thermal property and crystallization behavior of prepared copolymer were also studied.
Co-reporter:Julan Duan;Cuiqing Teng;Keqing Han;Wenxuan Wu;Qijin Zhang;Kin Seng Chiang
Polymer Engineering & Science 2009 Volume 49( Issue 9) pp:1865-1870
Publication Date(Web):
DOI:10.1002/pen.21375
Abstract
Fabrication of segmented cladding fiber (SCF) by bicomponent spinning was proposed in this article. In the new designed spin pack, we considered the high refractive component of cladding and core as a whole to control the cross section of the fiber. Quenching system in current bicomponent melting spinning system was modified according to the requirement of quenching fiber with a large size. The polymer SCF with required cross section was successfully fabricated using polycarbonate and polymethyl methacrylate. The transmission loss in the wavelength of 500–1000 nm was tested by the cut-back method. The result showed that the transmission loss of the obtained fiber was comparatively high, being up to 30 dB/m. The output light pattern of the obtained fiber of 60 cm was collected by using a charge-coupled device camera with laser light of 532 nm as the input. The output light pattern for the far field was a uniform circle and that for the near field was similar to the cross-section designed. The results showed that the obtained fiber was still a multimode optical fiber because of the comparatively large refractive index difference between the two materials used. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Co-reporter:Weixia Yan;KeQing Han;Hongmei Zhou
Journal of Applied Polymer Science 2006 Volume 99(Issue 3) pp:775-781
Publication Date(Web):11 NOV 2005
DOI:10.1002/app.22552
An in situ solid-state polymerization process was developed to produce long glass fiber reinforced poly(ethylene terephthalate) (PET) composites. As reported in our last article, one advantage of this new process is that the good wetting of reinforcing fiber can be obtained for using low-viscosity oligomer as raw materials. In this article, the grafting of PET macromolecular chain onto the surface of reinforcing glass fiber during in situ solid-state polycondensation (SSP) will be investigated, which was believed to be another advantage for this new process and should be very important for thermoplastic composite. The reinforcing glass fiber after removing ungrafted PET from a long glass fiber reinforced PET composite by solvent extraction was investigated by SEM, pyrolysis-gas chromatography mass spectrometry (Py-GC/MS), DSC, and FTIR. The information from morphology of SEM photos of glass fiber surface, the spectrum of Py-GC/MS, the melt peak at differential scanning calorimetric (DSC) curve, and the spectrum of Fourier transform infrared Raman spectroscopy (FTIR) gave a series evidence to prove the presence of grafted PET layer on the surface of silane-coupling-treated glass fiber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 775–781, 2006
Co-reporter:Keqing Han
Journal of Applied Polymer Science 2006 Volume 100(Issue 2) pp:1588-1593
Publication Date(Web):30 JAN 2006
DOI:10.1002/app.23312
Poly(ethylene phthalate) (PET)/nano-TiO2 composites prepared via in situ polymerization were spun into fiber by the melt-spinning process. The dispersion of nanosized rutile TiO2 in the PET was studied using transmission electron microscopy (TEM) and scanning probe microscopy (SPM) techniques. The mechanical properties and the properties of ultraviolet (UV) protection were investigated. The results showed that rutile TiO2 can be dispersed uniformly by the in situ polycondensation process. The mechanical properties of PET/TiO2 fiber were slightly affected by adding nano-TiO2. The UV-ray transmittance of PET/nano-TiO2 fabrics was below 10% in the UV-A band and below 1% in the UV-B band. And the ultraviolet protection factor (UPF) of PET/nano-TiO2 fabrics was greater than 50. All these PET/TiO2 nanocomposite fabrics exhibited excellent UV-blocking properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1588–1593, 2006
Co-reporter:Keqing Han;Wenjiang Li;Chengxun Wu
Polymer International 2006 Volume 55(Issue 8) pp:
Publication Date(Web):2 MAY 2006
DOI:10.1002/pi.2025
The rheological behavior of polyurethane (PU)/N,N-dimethylformamide (DMF) spinning solutions with various contents of hyperbranched polyesters was studied using a RS150L-controlled stress rotational rheometer. The results showed that the viscosity of the spinning solutions could be greatly reduced by adding hyperbranched polyesters even at 0.5 wt% loading. The zero-shear viscosity of solutions with hyperbranched polyesters was much lower than that of pure PU/DMF solution, which indicated a lower degree of entanglement when solutions were in a static state. The apparent activation energy of viscous flow and the critical shear rate for shear thinning of solutions with hyperbranched polyesters were much lower than that for pure PU/DMF solution, which indicated a weaker entanglement structure formed. In addition, the effect of hyperbranched polyesters on the mechanical properties of Spandex fiber was discussed. Copyright © 2006 Society of Chemical Industry
Co-reporter:Zheng-jun Liu;Ke-qing Han;Mu-huo Yu
Macromolecular Materials and Engineering 2005 Volume 290(Issue 7) pp:688-694
Publication Date(Web):30 JUN 2005
DOI:10.1002/mame.200500051
Summary: Long glass fiber reinforced PA6 (LGF/PA6) prepregs were prepared by impregnating PA6 oligomer melt into reinforcing glass fiber followed by subsequent solid-state polymerization (SSP) to obtain LGF/PA6 composite pellets. A conventional injection-molding machine suitable for short glass fiber reinforced composites was applied to the processing of the prepared composites, which reduced the fiber length in the final products. Mechanical properties, thermal property, and fiber length distribution of injection molding bars were investigated. Scanning electron microscopy (SEM) was used to observe the impact fracture surfaces and the surfaces of glass fiber after the SSP. It was found that the LGF/PA6 composites were of favorable mechanical properties, especially the impact strength, although the average length of glass fiber was rather short. By this novel process, the content of glass fiber in composite could be high up to 60 wt.-% and the maximum level of heat distortion temperature (HDT) was close to the melting temperature of PA6. SEM images indicated the favorable interfacial properties between the glass fiber and matrix. The glass fiber surfaces were further observed by SEM after removing the matrix PA6 with a solvent, the results showed that PA6 macromolecules were grafted onto the surface. Furthermore, the grafting amount of PA6 was increased with SSP time.
Co-reporter:Muhuo Yu;Cuiqing Teng
Journal of Applied Polymer Science 2005 Volume 97(Issue 2) pp:449-454
Publication Date(Web):26 APR 2005
DOI:10.1002/app.21715
High-strength polyethylene (HSPE) fibers were oxidated via chemical reactions in an acidic medium, and the carboxyl group was transferred into the acyl chloride and then reacted with pentaerythritol or diethylene triamine to graft the multifunctional group compounds onto the surface of the HSPE fibers. Subtractive Fourier transform infrared spectroscopy and the methylene blue absorbing method were used to study the functional groups on the surface of the modified fibers and their content. The results show that the polar functional groups, including COOH, OH, and NH2, were introduced onto the surface of the HSPE fibers, and the polar groups improved the wettability. The interface shear stress (IFSS) of the composites that were made from modified fibers and epoxy was measured by means of the microdebond method. The results show that the IFSS was greatly increased by the grafting of pentaerythritol or diethylene triamine onto the HSPE fiber surface. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 449–454, 2005
Co-reporter:Weizhen Xiao;Huimin Yu;Keqing Han
Journal of Applied Polymer Science 2005 Volume 96(Issue 6) pp:2247-2252
Publication Date(Web):6 APR 2005
DOI:10.1002/app.21703
Poly(ethylene terephthalate) (PET) and PET/montmorillonite(MMT) (2.5 wt %) nanocomposites with high molecular weight were prepared by solid-state polycondensation and their fiber was spun and drawn under various conditions. The influence of MMT nanomaterials on the thermal shrinkage of PET fiber was investigated and the structure was studied using the methods of WAXD, DSC, fiber orientation measurement, etc. The results showed that the MMT nanomaterials improved the thermal stability of microstructure of PET fiber. The fusion heat of PET/MMT was higher than that of PET, which generally implied the high orientation or high crystallinity. However, the degree of orientation and the crystallinity of PET/MMT fiber measured by WAXD were lower than that of pure PET fiber. It is suggested that the strong interaction between MMT layer and PET restricted the motions of PET molecular chains, which developed “a special continuous network structure” and prohibited the thermal shrinkage of PET fiber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2247–2252, 2005
Co-reporter:Huimin Yu;Keqing Han
Journal of Applied Polymer Science 2004 Volume 94(Issue 3) pp:
Publication Date(Web):26 AUG 2004
DOI:10.1002/app.20888
The effect of nanomaterials on the solid-state polycondensation (SSP) of PET was investigated using intrinsic viscosity measurement, wide-angle X-ray diffraction, differential scanning calorimetry, and polarizing microscope. The results showed that the montmorillonite nanomaterials could greatly increase the rate of solid-state polycondensation of PET, probably due to the nucleation of montmorillonite nanomaterials for PET crystallization, which resulted in lower crystallinity, more small crystals, and more surfaces of the crystals. The surfaces of microcrystal and richer amorphous regions benefitted the polycondensation reaction of PET and diffusion of volatile by-products, which led to the higher rate of SSP. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 971–976, 2004
Co-reporter:Cuiqing Teng;Ping Ji;Kai Yang
Journal of Polymer Science Part A: Polymer Chemistry 2004 Volume 42(Issue 20) pp:5045-5053
Publication Date(Web):3 SEP 2004
DOI:10.1002/pola.20412
An Erratum has been published for this article in J. Polym. Sci. Part A: Polym. Chem. (2004) 42(22) 5845
New multiblock copolymers derived from poly(L-lactic acid) (PLLA) and poly(ε-caprolactone) (PCL) were prepared with the coupling reaction between PLLA and PCL oligomers with NCO terminals. Fourier transform infrared (FTIR), 13C NMR, and differential scanning calorimetry (DSC) were used to characterize the copolymers and the results showed that PLLA and PCL were coupled by the reaction between NCO groups at the end of the PCL and OH (or COOH) groups at the end of the PLLA. DSC data indicated that the different compositions of PLLA and PCL had an influence on the thermal and crystallization properties including the glass-transition temperature (Tg), melting temperature (TM), crystallizing temperature (Tc), melting enthalpy (ΔHm), crystallizing enthalpy (ΔHc), and crystallinity. Gel permeation chromatography (GPC) was employed to study the effect of the composition of PLLA and PCL and reaction time on the molecular weight and the molecular weight distribution of the copolymers. The weight-average molecular weight of PLLA–PCL multiblock copolymers was up to 180,000 at a composition of 60% PLLA and 40% PCL, whereas that of the homopolymer of PLLA was only 14,000. A polarized optical microscope was used to observe the crystalline morphology of copolymers; the results showed that all polymers exhibited a spherulitic morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5045–5053, 2004
Co-reporter:Yuqing Peng, Kaishi Wang, Muhuo Yu, Aijun Li, Rajendra K. Bordia
Ceramics International (March 2017) Volume 43(Issue 4) pp:
Publication Date(Web):March 2017
DOI:10.1016/j.ceramint.2016.12.045
A reliable and optimized process to grow carbon nanotubes (CNTs) in templated pores of polymer derived ceramic (PDC) matrix was developed. It is realized through the pyrolysis of a preceramic polymer, i.e., poly (methyl-phenyl-silsesquioxane) (denoted as PMPS), in argon atmosphere at 1000 °C together with nickel-catalyst-coated poly-methyl-methacrylate (PMMA) microbeads (denoted as PMMA-Ni). PMPS served as both a precursor for the ceramic matrix and a carbon source for the CNT growth. PMMA microbeads were used as sacrificial pore formers and coated with nickel via an electroless plating method, which provides an improved control of particle size of the catalyst and its distribution in the material. The influence of PMMA-Ni loading on the in situ growth of CNTs and the properties of CNTs/SiOC nanocomposites were studied through thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and density/porosity measurements. Under optimized conditions, uniform distribution of in situ grown CNTs was observed within the templated pores of the SiOC matrix. The optimized process leads to reproducible high yield of CNTs in the pores. The development of such novel CNT/cellular ceramic nanocomposite materials is of significant interest for a variety of sensor applications.
![N-[BIS(METHYLAMINO)BORANYL]METHANAMINE](http://img.cochemist.com/ccimg/7400/7397-44-6.png)
![N-[BIS(METHYLAMINO)BORANYL]METHANAMINE](http://img.cochemist.com/ccimg/7400/7397-44-6_b.png)
![N-[TRIS(METHYLAMINO)SILYL]METHANAMINE](http://img.cochemist.com/ccimg/32000/31978-09-3.png)
![N-[TRIS(METHYLAMINO)SILYL]METHANAMINE](http://img.cochemist.com/ccimg/32000/31978-09-3_b.png)
