Co-reporter:Liang Gao;Qingjie Zhang;Hao Li;Siruo Yu;Weihong Zhong;Gang Sui
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 13) pp:2016-2027
Publication Date(Web):2017/03/28
DOI:10.1039/C7PY00063D
The curing kinetics and thermo-mechanical characteristics of two kinds of high-performance amine cured tri-functional epoxy resin compounds, including diglycidyl-4,5-epoxycyclohexane-1,2-dicarboxylate and N,N-diglycidyl-4-glycidyloxyaniline, were systematically studied herein. Different to the simple bi-functional epoxy resins studied before, the increase in epoxy functionality and resultant asymmetric monomer structure made the whole curing behaviour more difficult to analyse. Nevertheless, there is an urgent demand to provide a thorough understanding of the tri-functional epoxy resin/amine system in order to obtain the desired macro-performance. In this paper, a methodology, which combines atomistic molecular simulation with experimental research, was established to expound the effect of the asymmetric epoxy monomer structure on the reaction kinetics and ultimate performance of the tri-functional epoxy/amine system. It can be utilized to efficiently analyse the cross-linking procedure and the microstructure–property relationships of epoxy resin with poly-functionality and asymmetric monomer structures, thereby serving as guidance to design high-performance polymer matrices for advanced composites.
Co-reporter:Yuqiang Jin;Haocheng Yuan;Jin-Le Lan;Yunhua Yu;Yuan-Hua Lin
Nanoscale (2009-Present) 2017 vol. 9(Issue 35) pp:13298-13304
Publication Date(Web):2017/09/14
DOI:10.1039/C7NR04912A
High gravimetric energy density and volumetric energy density energy storage devices are highly desirable due to the rapid development of electric vehicles, and portable and wearable electronic equipment. Electrospinning is a promising technology for preparing freestanding electrodes with high gravimetric and volumetric energy density. However, the energy density of the traditional electrospun electrodes is restricted by the low mass loading of active materials (e.g. 20%–30 wt%). Herein, a biomimetic strategy inspired by the phenomenon of the sticky spider web is demonstrated as a high performance anode, which simultaneously improves the gravimetric and volumetric energy density. Freestanding carbon nanofiber (CNF) membranes containing over 50 wt% of bismuth were prepared by electrospinning and subsequent thermal treatment. Membranes consisting of CNF network structures bonded tightly with active Bi cluster materials, resulting in excellent mechanical protection and a fast charge transport path, which are difficult to achieve simultaneously. The composite membrane delivers high reversible capacity (483 mA h g−1 at 100 mA g−1 after 200 cycles) and high rate performance (242 mA h g−1 at 1 A g−1) as a lithium-ion battery anode. For use as a sodium ion battery, the composite membrane also shows a high reversible specific capacity of 346 mA h g−1 and outstanding cycling performance (186 mA h g−1 at 50 mA g−1 after 100 cycles). This work offers a simple, low cost and eco-friendly method for fabricating free-standing and binder-free composite electrodes with high loading used in LIBs and SIBs.
Co-reporter:Qing Cai, Yuzhou Shi, Dingying Shan, Wenkai Jia, Shun Duan, Xuliang Deng, Xiaoping Yang
Materials Science and Engineering: C 2015 Volume 55() pp:166-173
Publication Date(Web):1 October 2015
DOI:10.1016/j.msec.2015.05.002
•Magnetic nanofibers containing well-dispersed Fe3O4 nanoparticles were produced.•Static magnetic field (SMF) was applied to perform the culture of osteoblasts.•Osteogenic differentiation was enhanced on magnetic substrate with exposure to SMF.Proliferation and differentiation of bone-related cells are modulated by many factors such as scaffold design, growth factor, dynamic culture system, and physical simulation. Nanofibrous structure and moderate-intensity (1 mT–1 T) static magnetic field (SMF) have been identified as capable of stimulating proliferation and differentiation of osteoblasts. Herein, magnetic nanofibers were prepared by electrospinning mixture solutions of poly(l-lactide) (PLLA) and ferromagnetic Fe3O4 nanoparticles (NPs). The PLLA/Fe3O4 composite nanofibers demonstrated homogeneous dispersion of Fe3O4 NPs, and their magnetism depended on the contents of Fe3O4 NPs. SMF of 100 mT was applied in the culture of MC3T3-E1 osteoblasts on pure PLLA and PLLA/Fe3O4 composite nanofibers for the purpose of studying the effect of SMF on osteogenic differentiation of osteoblastic cells on magnetic nanofibrous scaffolds. On non-magnetic PLLA nanofibers, the application of external SMF could enhance the proliferation and osteogenic differentiation of MC3T3-E1 cells. In comparison with pure PLLA nanofibers, the incorporation of Fe3O4 NPs could also promote the proliferation and osteogenic differentiation of MC3T3-E1 cells in the absence or presence of external SMF. The marriage of magnetic nanofibers and external SMF was found most effective in accelerating every aspect of biological behaviors of MC3T3-E1 osteoblasts. The findings demonstrated that the magnetic feature of substrate and microenvironment were applicable ways in regulating osteogenesis in bone tissue engineering.
Co-reporter:Xiaodong Yan, Yunhua Yu, Seung-Kon Ryu, Jinle Lan, Xiaolong Jia, Xiaoping Yang
Electrochimica Acta 2014 Volume 136() pp:466-472
Publication Date(Web):1 August 2014
DOI:10.1016/j.electacta.2014.05.031
Phosphorus and nitrogen enriched porous carbons were fabricated by direct heat treatments of the honeycomb-patterned H3PO4/polyacrylonitrile composite precursors obtained through solvent evaporation. Surface chemistry analysis showed that high surface concentrations of phosphorus and nitrogen as well as the desirable chemical structures can be achieved by controlling the carbonization temperature. Electrochemical measurements in 1 M H2SO4 aqueous electrolyte showed that the gravimetric capacitance and the volumetric capacitance reached as high as 205.7 F g−1 and 261 F cm−3 at 0.5 A g−1, respectively. In particular, the capacitance showed no degradation even after 8000 charge/discharge cycles, clearly demonstrating a robust long-term stability. The excellent electrochemical performance makes the electrode material a promising candidate for supercapacitors.
Co-reporter:Lan Huang, Xiaoping Yang, Xiaolong Jia and Dapeng Cao
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 45) pp:24892-24898
Publication Date(Web):06 Oct 2014
DOI:10.1039/C4CP03120B
Owing to the wide application of polymeric materials, understanding the fracture mechanism of amorphous polymers at strain fields is a fundamentally important challenge. In this work, we use molecular dynamics simulations to investigate the uniaxial deformation of amorphous polyethylene and further monitor the polyethylene fracture process induced by stretching. Results indicate that the polyethylene systems with chain lengths of 600–800 united atoms exhibit the fracture behavior at a temperature T < 200 K and the strain of 1.0. Further study shows that in the stretching process, the disentanglement and orientation of chains lead to the formation of small cavities in the middle region of the system, and the small cavities subsequently form a large hole, causing the fracture of the whole system. Definitely, the fracture is determined by the two factors of mobility and entanglement of chains. The polyethylene systems with a high chain mobility or a high chain entanglement do not fracture. Finally, a schematic diagram is put forward to illustrate the fracture behavior.
Co-reporter:Donghua Teng, Yunhua Yu and Xiaoping Yang
RSC Advances 2014 vol. 4(Issue 24) pp:12309-12312
Publication Date(Web):10 Feb 2014
DOI:10.1039/C3RA47685E
A hierarchical flower-like TiO2/MPCNFs web was cost-effectively fabricated by electrospinning, solvothermal treatment and calcination. The flower-like TiO2/MPCNFs as a free-standing anode possessed superior cycling reversibility and rate capability to nano-particulate and micro-particulate TiO2/MPCNFs because of its unique multiporous micro-/nano-architecture for synergistic lithium storage.
Co-reporter:Qing Cai, Jifu Mao, Xiaoli Li, Xiaoping Yang
Materials Letters 2014 Volume 128() pp:238-241
Publication Date(Web):1 August 2014
DOI:10.1016/j.matlet.2014.04.164
•Chemical modification of multiwalled carbon nanotubes (MWCNTs) with phosphorylation.•Evenly coating phosphorylated MWCNT׳s surface with CaP depositions (MWCNTs-CaP).•Macroporous PLLA scaffolds with nanofibrous pore walls reinforced with MWCNTs-CaP.Scaffolds with both macro- and nanoscale structures have shown promise in tissue engineering; however, their mechanical properties are not satisfactory for load-bearing bone regeneration. In this study, calcium phosphate-coated multiwalled carbon nanotubes (MWCNTs-CaP) were developed to reinforce macroporous poly(L-lactide) (PLLA) scaffolds with nanofibrous pore walls. The scaffolds were prepared using a phase separation/particle-leaching method. One-dimensional MWCNTs-CaP were prepared via phosphorylation and mineralization. The addition of the MWCNTs-CaP did not affect the nanofibrous pore walls of the resulting PLLA scaffolds. In comparison with pure PLLA scaffolds, the compressive properties of PLLA/MWCNTs-CaP composite scaffolds were significantly improved, indicating their potential in bone regeneration applications.
Co-reporter:Donghua Teng, Yunhua Yu, Peiwen Li, Xiang Bai and Xiaoping Yang
RSC Advances 2013 vol. 3(Issue 34) pp:14237-14240
Publication Date(Web):18 Jun 2013
DOI:10.1039/C3RA42182A
A novel Ti3O5/TiP2O7@MPCNFs nanocomposite was facilely prepared by electrospinning, sol–gel ripening and H3PO4 pre-impregnation activation treatment. The Ti3O5/TiP2O7@MPCNFs as a binder-free anode showed a synergistic lithium storage effect due to its topographical surface morphology, hierarchical nanostructure and special heterogeneous composition.
Co-reporter:Qing Cai, Qiaofang Feng, Haiyang Liu, Xiaoping Yang
Materials Letters 2013 Volume 91() pp:275-278
Publication Date(Web):15 January 2013
DOI:10.1016/j.matlet.2012.09.101
In this study, poly(l-lactic acid)/gelatin composite fibrous matrixes were prepared by electrospinning and were immersed in five times simulated body fluid (SBF) to induce flaky-like minerals depositing on fiber surface. After being subjected to calcination, the flaky-like apatite minerals transformed into hexagonal hydroxyapatite (HA) crystals under proper sintering temperature and time along with the complete removal of organic fibers. The obtained hexagonal HA crystals demonstrated similar morphology and crystallinity to those obtained by calcining antlers and human tibia. The results suggested that the combination of biomineralization and calcination was a possible way to produce biomimetic calcium-phosphate apatite in vitro, which had wide use in bone tissue engineering.Highlights► Preparation of hexagonal-shaped hydroxyapatite resembling the structure of minerals from antlers and human tibia. ► Preparation of biomimetic hexagonal-shaped hydroxyapatite by combining biomineralization and calcination. ► Using electrospun poly(l-lactide)/gelatin composite fibers as substrates for biomineralization.
Co-reporter:Xiaolong Jia, Baiyang Liu, Lan Huang, David Hui, Xiaoping Yang
Composites Part B: Engineering 2013 Volume 54() pp:133-137
Publication Date(Web):November 2013
DOI:10.1016/j.compositesb.2013.04.002
A novel nanostructural hybrid (SiO2–MWCNTs) composed of zero-dimensional silica nanoparticles (SiO2) and one-dimensional multi-walled carbon nanotubes (MWCNTs) were successfully prepared by multi-step functionalization. Synergistic reinforcing effect of SiO2–MWCNTs on epoxy-based composites was investigated using various theoretical methods. Specifically, a novel finite element method (FEM) based on nanoscale representative volume element (RVE) model was built up to describe the irregular geometry and reinforcing effect of SiO2–MWCNTs. In contrast with the corrected rule of mixtures and corrected Halpin–Tsai equations, the established FEM based on nanoscale RVE model was highly accurate and effective in predicting mechanical properties for polymer-based composites reinforced by SiO2–MWCNTs.
Co-reporter:Xiaolong Jia, Zigao Zeng, Gang Li, David Hui, Xiaoping Yang, Shiren Wang
Composites Part B: Engineering 2013 Volume 54() pp:234-240
Publication Date(Web):November 2013
DOI:10.1016/j.compositesb.2013.05.005
Effects of epoxy phenolic resin (EPR) on ablative and interfacial bonding properties of EPDM composites were evaluated. Ablative properties of EPDM composites were enhanced by two folds with incorporating 10 phr EPR. This significant enhancement was attributed to positive effect of EPR on thermal stability and thermal insulating properties of EPDM composites as well as formation of compact char layer onto composites. Furthermore, interfacial shear strength of EPDM composites with carbon fiber/epoxy (CF/EP) composites was increased by 55.6% with incorporating 10 phr EPR, due to interfacial chemical reaction of epoxide groups of EPR molecule from EPDM composites with amine group of hardener from CF/EP composites.
Co-reporter:Song Lin, Xiaolong Jia, Hongjie Sun, Hongwei Sun, David Hui, Xiaoping Yang
Composites Part B: Engineering 2013 Volume 46() pp:227-233
Publication Date(Web):March 2013
DOI:10.1016/j.compositesb.2012.09.067
Mechanical properties of composite pressure vessels under thermo-mechanical conditions were performed by a hydraulic and atmospheric pressure test, respectively. During atmospheric fatigue test, the temperature of the gas and vessel varied remarkably with the pressure, indicating that the vessel was under thermo-mechanical cyclic loadings. Besides, the mechanical properties of the filament wound resin matrix and composition-dependent composites varied significantly throughout the temperature changing range, which could stimulate more damages to the vessel during atmospheric fatigue test than that during hydraulic test characterized by acoustic emission. These damages might lead to a reduction in the final burst pressure of the vessel by 9.6%.
Co-reporter:Gang Li, Xiaolong Jia, Zhibin Huang, Bo Zhu, Peng Li, Xiaoping Yang, Wuguo Dai
Materials Chemistry and Physics 2012 Volume 134(2–3) pp:958-965
Publication Date(Web):15 June 2012
DOI:10.1016/j.matchemphys.2012.03.098
MWNTs-EP were successfully prepared by functionalization of MWNTs with epoxy-based groups, and MWNTs-EP/polysulfone (PSF) hybrid nanofibers were fabricated to obtain ex-situ dispersion and alignment of MWNTs-EP by electrospinning. The prescribed morphology and interface correlation of hybrid nanofibers reinforced and toughened epoxy matrix (RTEP) were investigated. The alignment degree of hybrid nanofibers was enhanced with increasing MWNTs-EP loadings, and MWNTs-EP were found to be well dispersed and aligned along the nanofiber axis. The dispersion and alignment states of MWNTs-EP during inhomogeneous phase separation of RTEP were proposed and verified. MWNTs-EP dispersed and aligned along the orginal nanofiber axis were enveloped, bridged or pinned by PSF spheres arranged in the nanofiber direction. The interface chemical correlation between MWNTs-EP and resin matrix was generated due to the further reaction of epoxide rings on the surface of MWNTs-EP, which resulted in simultaneous improvement of mechanical and thermal properties of RTEP.Highlights► The ex-situ dispersion and alignment of MWNTs-EP were obtained by electrospinning. ► MWNTs-EP/PSF hybrid nanofibers were used to reinforce and toughen epoxy matrix. ► The prescribed morphology of reinforced and toughened epoxy were proposed and verified. ► The interface chemical correlation between MWNTs-EP and epoxy matrix was generated. ► The simultaneous improvement of mechanical and thermal properties were achieved.
Co-reporter:Bingxue Liu, Yunhua Yu, Jie Chang, Xiujuan Yang, Dezhen Wu, Xiaoping Yang
Electrochemistry Communications 2011 Volume 13(Issue 6) pp:558-561
Publication Date(Web):June 2011
DOI:10.1016/j.elecom.2011.03.009
A new core-shell coaxial carbon nanofibers web (C-CNFW), exhibiting high carbon purity (without any binders), structural integrity, enhanced stability under different current loads, long cycling life, large reversible capacity (over 520 mA h g− 1), excellent capacity retention and good rate capability, is fabricated by coaxial electrospinning and subsequent carbonization. It is envisaged that the superior electrochemical properties of C-CNFW will make it a promising candidate for the anode material of high-power lithium-ion batteries (LIBs), owing to the unique combinative effects of core carbon material from mineral oil and sheath carbon material from PAN.Research Highlights► A novel core-shell coaxial carbon nanofibers web (C-CNFW) is fabricated. ► The C-CNFW presents a reversible capacity about 520 mA h g− 1. ► After 80 cycles, the coaxial structure of the nanofibers is enhanced stable. ► The C-CNFW can keep a desirable structural integrity.
Co-reporter:Bo Wang, Qing Cai, Shen Zhang, Xiaoping Yang, Xuliang Deng
Journal of the Mechanical Behavior of Biomedical Materials 2011 Volume 4(Issue 4) pp:600-609
Publication Date(Web):May 2011
DOI:10.1016/j.jmbbm.2011.01.008
In this study, poly (L-lactic acid) (PLLA)/trifluoroethanol (TFE) solution was electrospun to fabricate fibrous scaffolds with different fiber orientations. Random and parallel PLLA nanofiber alignments were achieved by using a metal plate and a rolling rod as the receiver, respectively. The parallel PLLA fibrous scaffolds were further hot-stretched to obtain hyperparallel PLLA fibrous scaffolds. The PLLA fibrous scaffolds were characterized by fiber diameter, interfiber distance, fiber array angle, water contact angle, morphology and mechanical strength. The tensile strength of hyperparallel nano-fibers was approximately 5- and 14-times the parallel and random fibers, respectively. Osteoblast-like MG63 cells were cultured on the PLLA scaffolds to study the effects of fiber orientation on cell morphology, proliferation and differentiation. The cells on the randomly-oriented scaffolds showed irregular forms, while the cells exhibited shuttle-like shapes on the parallel scaffolds and had larger aspect ratios along the fiber direction of the hyperparallel scaffolds. Alkaline phosphatase (ALP) activity and collagen I (placeStateCol I) and osteocalcin (OC) deposition exhibited fiber orientation dependence. With an increase in parallelism of the fibers, there was a decrease in ALP activity and placeStateCol I and OC production. These results suggest that exploitation of PLLA fiber orientation may be used to control osteoblast-like cell responses.
Co-reporter:Qing Cai, Qingqing Xu, Qiaofang Feng, Xiaoyan Cao, Xiaoping Yang, Xuliang Deng
Applied Surface Science 2011 Volume 257(Issue 23) pp:10109-10118
Publication Date(Web):15 September 2011
DOI:10.1016/j.apsusc.2011.06.157
Abstract
To promote the biomineralization, supersaturated simulated body fluids (SBFs), e.g. five times SBF (5 × SBF), were usually applied. In these SBFs, however, homogeneous nucleation of Ca–P mineralites and deposition unavoidably took place owing to the HCO3− decomposition and the pH value increment, which made the prediction of bone bioactivity of substrates controversial. In this study, the classically prepared 5 × SBF was continuously bubbled with CO2 to keep the pH value stable at 6.4 and the solution transparent, and a kind of electrospun poly(l-lactic acid)/gelatin composite fibers was used for the biomineralization study. In such a modified 5 × SBF, heterogenenous nucleation occurred dominantly and thermodynamical unstable brushites (dicalcium phosphate dihydrate, DCPD) were detected shortly on both electrospun PLLA fibers and PLLA/gelatin (1:1 in weight) composite fibers. In comparison with electrospun PLLA fibers, the sheet-like DCPD mineralites transformed into flaky carbonated calcium-deficient hydroxyapatite (CDHA) within 24 h on the PLLA/gelatin composite fibers due to the accelerating effect of gelatin component. The formed apatite coating contained much less Mg2+ ions than that deposited in the classical 5 × SBF. The results of this study showed that supersaturated SBFs buffered with gassy CO2 were expected good choices for the accelerated biomineralization, and for the prediction of the bone bonding bioactivity of substrates.
Co-reporter:Yanan Li;Yunhua Yu;Xiaolong Jia;Shun Duan
Polymer Composites 2011 Volume 32( Issue 12) pp:1953-1960
Publication Date(Web):
DOI:10.1002/pc.21225
Abstract
The corrosion mechanism of glass-fiber reinforced vinyl ester composites was investigated by immersing composite samples in 40 wt% sulfuric acid solution at constant temperature of 35°C, 55°C, 65°C, and 75°C for periods up to 10,500 h. Results were characterized through weight gain tests, inductively coupled plasma analysis, and scanning electron microscope (SEM). Weight gains and ion-leaching behaviors show that the composite interface has undergone significant changes due to a long corrosive environment, and the interface corrosion of composite increases with increasing the temperature. SEM images of surface and cross-section of samples indicated that there exit in irreversible degradation reaction on resin matrix and interface in composite, which lead to the increase of weight gain and ion leachability, especially at high temperatures. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers
Co-reporter:Haiyang Liu, Qing Cai, Pengfei Lian, Zhou Fang, Shun Duan, Seungkon Ryu, Xiaoping Yang, Xuliang Deng
Carbon 2010 Volume 48(Issue 8) pp:2266-2272
Publication Date(Web):July 2010
DOI:10.1016/j.carbon.2010.02.042
Carbon nanofibers decorated with β-tricalcium phosphate (β-TCP) nanoparticles (β-TCP/CNFs) have been prepared by sintering electrospun polyacrylonitrile fibers with calcium nitrate tetrahydrate as the calcium source and triethyl phosphate as the phosphorus source. Microstructure and phase composition analysis indicate that the resulting materials are composed of β-TCP nanoparticles and CNFs. And the long β-TCP/CNFs can be cut into organism-eliminable short CNFs gradually in hydrochloric acid solution due to the solubilization of β-TCP nanoparticles. The materials exhibit good biocompatibility, and have comparable effect on cell growth with pure CNFs, with their tuning ability in degradation.
Co-reporter:Yunhua Yu, Qing Yang, Donghua Teng, Xiaoping Yang, Seungkon Ryu
Electrochemistry Communications 2010 Volume 12(Issue 9) pp:1187-1190
Publication Date(Web):September 2010
DOI:10.1016/j.elecom.2010.06.015
Reticular tin nanoparticle-dispersed carbon (Sn/C) nanofibers were fabricated by stabilization of electrospun SnCl4/PAN composite fibers and subsequent carbonization at different temperatures. These Sn/C composite nanofibers used as anode materials for rechargeable lithium-ion batteries (LIBs) show that the Sn/C nanofibers at 700 and 850 °C present much higher charge (785.8 and 811 mA h g−1) and discharge (1211.7 and 993 mA h g−1) capacities than those at 550 and 1000 °C and the as-received CNFs at 850 °C, corresponding to coulombic efficiencies of 64.9% and 81.7%, respectively. The superior electrochemical properties of the intriguing Sn/C nanofibers indicate a promising application in high performance Li-ion batteries.
Co-reporter:Xuegang Zhou;Qing Cai;Na Yan;Xuliang Deng
Journal of Biomedical Materials Research Part A 2010 Volume 95A( Issue 3) pp:
Publication Date(Web):
DOI:10.1002/jbm.a.32896
Abstract
A common problem in applying electrospun biodegradable polyester matrixes as tissue-engineering scaffolds is their serious shrinkage with degradation to reduce the porosity drastically. To ameliorate this problem, a nestlike-patterned poly(D,L-lactide-co-glycolide) (PLGA) nanofibrous (∼900 nm) matrix was proposed and fabricated by electropinning. Shrinkage studies demonstrated that the dimension change of nestlike-patterned fibrous membrane was much smaller than those of nonwoven and parallel-aligned fibrous membranes. And the robust framework of the patterned matrix helped to maintain its original nestlike topographical structure during degradation. Compared to hydrolytic-degraded specimens, the PLGA nanofibrous matrixes degraded in the presence of lysozyme showed larger weight loss but slower decrease in molecular weight. Besides, porous fibers with intact surface were detected by scanning electron microscopy after 20-week hydrolysis, and fibers with pores both inside and on surface were observed after enzymatic degradation for 12 weeks. Accordingly, the former presented a bimodal gel permeation chromatography (GPC) peak, while no bi or multimodal GPC peaks were found for the latter as degradation proceeded. These results indicated that an acid autocatalytic effect still existed in the hydrolysis of PLGA nanofibrous matrix. The presence of lysozyme could only accelerate the dissolution of degradation products with low molecular weight, but have no contribution to the chain scission. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010.
Co-reporter:Xiaolong Jia;Yunhua Yu;Gang Li;Gang Sui;Peng Li
Journal of Applied Polymer Science 2010 Volume 118( Issue 2) pp:1060-1067
Publication Date(Web):
DOI:10.1002/app.32332
Abstract
The effects of three curing systems and polysulfonamide (PSA) pulp on the curing characteristics, mechanical properties, and swelling behavior of ethylene–propylene–diene elastomer (EPDM) composites were investigated. The maximum torque value and the optimum curing time were highest for EPDM composites cured with a peroxide system, and they were closely followed by those cured with a sulfur system. In comparison with those cured with peroxide and phenolic resin systems, EPDM composites cured with the sulfur system showed higher mechanical properties and dimensional stability. With increasing PSA pulp content, the maximum torque value of the EPDM composites increased, whereas the optimum curing time of the composites decreased. The orientation percentage of the PSA pulp in the EPDM composites was maximum at 30 phr pulp, as determined from green strength measurements. In the longitudinal direction along which the pulp was oriented, the EPDM composites showed higher tensile strength as well as lower elongation and swelling ratios. Also, with increasing PSA pulp content, the tensile strength of the EPDM composites decreased up to 10 phr pulp and subsequently increased, whereas the elongation and swelling ratio of the EPDM composites decreased linearly. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Haiyang Liu, Qing Cai, Pengfei Lian, Zhou Fang, Shun Duan, Xiaoping Yang, Xuliang Deng, Seungkon Ryu
Materials Letters 2010 Volume 64(Issue 6) pp:725-728
Publication Date(Web):31 March 2010
DOI:10.1016/j.matlet.2009.12.050
β-tricalcium phosphate nanoparticles adhered carbon nanofibrous (β-TCP@CNFs) membranes were prepared by electrospinning and sintering a mixed solution of triethylphosphate, calcium nitrate tetrahydrate, and PAN. Crystalline structure and morphology of β-TCP@CNFs were characterized by XRD, SEM, and TEM observations. The diameter of the β-TCP nanoparticles was in the range of 30–60 nm, they were well distributed on the surface of CNFs. Human osteoblasts cells were actively proliferated on the β-TCP@CNFs membrane due to the far extended adhesion area and biocompatibility.
Co-reporter:Shen Zhang;Yaqin Huang;Fang Mei;Qi Ma;Guoqiang Chen;Seungkon Ryu;Xuliang Deng
Journal of Biomedical Materials Research Part A 2009 Volume 90A( Issue 3) pp:671-679
Publication Date(Web):
DOI:10.1002/jbm.a.32136
Abstract
The electrospinning of gelatin aqueous solution was successfully carried out by elevating the spinning temperature. The effects of spinning temperature and solution concentration were investigated on the morphology of gelatin nanofibers in the current study. To improve the stability and mechanical properties in moist state, the gelatin nanofibrous membrane was chemically crosslinked by 1-ethyl-3-dimethyl-aminopropyl carbodiimide hydrochloride and N-hydroxyl succinimide. The concentration of crosslinker was optimized by measuring the swelling degree and weight loss. Nanofibrous structure of the membrane was retained after lyophilization, although the fibers were curled and conglutinated. Tensile test revealed that the hydrated membrane becomes pliable and provides predetermined mechanical properties. Periodontal ligament cells cultured on the membrane in vitro exhibited good cell attachment, growth, and proliferation. Gelatin nanofibrous membrane can be one of promising biomaterials for the regeneration of damaged periodontal tissues. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Co-reporter:Yunhua Yu;Peng Li;Gang Sui;Hongliang Liu
Polymer Composites 2009 Volume 30( Issue 10) pp:1458-1464
Publication Date(Web):
DOI:10.1002/pc.20712
Abstract
Hygrothermal aging was carried out on vinyl ester (VE) resin cast and its pultruded carbon fiber reinforced composite (CF/VE) by immersing them in distilled water at 65 and 95°C. Hygrothermal aging effects on the samples were studied in terms of thermal–mechanical properties, as well as moisture absorption behavior, interfacial adhesion, and transverse mechanical properties. Moisture absorption behaviors of the VE casts and the CF/VE composites were characterized as Fickian behavior. Dynamic mechanical thermal analysis (DMTA) tests showed that the tan δ peak temperatures of the VE casts and CF/VE composites decreased with immersion time at 65 and 95°C. Moreover, there existed a splitting in the tan δ peaks at 95°C, which was reversible and could be recovered by dehydration. Three-point flexural test indicated that flexural strengths of both the VE casts and the composites decreased by hygrothermal aging with a trend related to their moisture absorption behaviors, while flexural modulus of the composites was less affected. The ILSS of the CF/VE composites was also depressed by deterioration in interfacial adhesion, which was proved by the interfacial adhesion parameters, A and α. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers
Co-reporter:Xiaolong Jia;Gang Li;Yunhua Yu;Gang Sui;Haiyang Liu;Ya'nan Li;Peng Li
Journal of Applied Polymer Science 2009 Volume 113( Issue 1) pp:283-289
Publication Date(Web):
DOI:10.1002/app.29470
Abstract
Polysulfonamide (PSA) short fiber/ethylene–propylene–diene elastomer (EPDM) composites were prepared as high-performance thermal insulators. The pyrolysis products and thermal stabilities of the PSA fiber and aramid fiber were analyzed. The ablation and thermal properties of the PSA/EPDM composites were compared with those of the aramid/EPDM composites. The degradation peak temperature of the PSA fiber was 100°C higher than that of the aramid fiber. With the fiber content increasing, the ablation rates of both composites decreased up to 10 phr and subsequently increased, whereas the thermal conductivities of both composites increased linearly. In comparison with the aramid/EPDM composites, the ablation rate and thermal conductivity of the PSA/EPDM composites were lower, whereas the thermal degradation temperature and limiting oxygen index of the PSA/EPDM composites were higher. Dynamic mechanical thermal testing and morphology observations revealed that strong interfacial bonding between the fiber and the matrix was developed in the PSA/EPDM composites, and it was beneficial for improving the ablation properties of the composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Gang Li, Zhibin Huang, Chunling Xin, Peng Li, Xiaolong Jia, Binghui Wang, Yadong He, Seungkon Ryu, Xiaoping Yang
Materials Chemistry and Physics 2009 Volume 118(2–3) pp:398-404
Publication Date(Web):15 December 2009
DOI:10.1016/j.matchemphys.2009.08.001
The phase separation process and morphology evolution of 5 wt% polysulfone (PSF) nanofibrous membranes toughened epoxy resin at different temperatures were investigated by synchrotron radiation small angel X-ray scattering (SR-SAXS), phase contrast microscopy (PCM) and scanning electron microscopy (SEM). The onset time of phase separation obtained by different methods was basically identical. As the curing proceeded at constant temperature, the scattering peak corresponding to the maximum scattering intensity shifted to a smaller scattering vector (qm), and the average diameters of PSF spheres increased, which showed a phase separation pattern of nucleation and growth mechanism. PSF spheres exhibited random alignment in “sea-island” morphology, which was attributed to the in situ phase separation of PSF nanofibers. Also, the effects of phase separation kinetics on the phase morphology and fracture toughness of nanofibrous membranes toughened epoxy resin were investigated. Results showed that the phase separation process was faster than the curing reaction process, which implied that the diffusion coefficient of PSF in epoxy resin increased with increasing the curing temperature, resulting in the increase of PSF sphere size that in turn improved the fracture toughness at higher temperature.
Co-reporter:Jianying Ji, Gang Sui, Yunhua Yu, Yanxin Liu, Yuanhua Lin, Zhongjie Du, Seungkon Ryu and Xiaoping Yang
The Journal of Physical Chemistry C 2009 Volume 113(Issue 12) pp:4779-4785
Publication Date(Web):2017-2-22
DOI:10.1021/jp8077198
Continuous macroscopic aligned polyacrylonitrile (PAN) composite nanofiber sheets embedded with highly aligned PAN-grafted multiwalled carbon nanotubes (MWCNTs) have been prepared by electrospinning followed by hot-stretching. Homogeneous and highly aligned MWCNTs in the polymer matrix were obtained by hot-stretching of the electrospun fibers, which led to a significant enhancement in the mechanical performance of the resulting composite nanofiber sheets. After hot-stretching, the tensile strength and modulus of an electrospun PAN nanofiber sheet (containing 2 wt % grafted MWCNTs) increased by 320.7% and 204.5%, respectively, compared with the values for the pristine PAN terpolymer. In addition we show, for the first time, that a Raman mapping method can be successfully employed to investigate the distribution and alignment of MWCNTs in nanofiber sheets.
Co-reporter:Song Lin, Qing Cai, Jianying Ji, Gang Sui, Yunhua Yu, Xiaoping Yang, Qi. Ma, Yan Wei, Xuliang Deng
Composites Science and Technology 2008 Volume 68(15–16) pp:3322-3329
Publication Date(Web):December 2008
DOI:10.1016/j.compscitech.2008.08.033
PAN core–PMMA shell nanofiber fabric was prepared by electrospinning of polymer blends to reinforce 2,2-bis-[4-(methacryloxypropoxy)-phenyl]-propane (Bis-GMA) a dental resin system. The core–shell structure of the PAN–PMMA nanofiber was confirmed by scanning electron microscopy (SEM) and transmission electron microscope/energy dispersive spectroscopy (TEM/EDS) observation. The flexural properties and dynamic mechanical properties of the PAN–PMMA nanofiber reinforced Bis-GMA composites were studied. Results showed that PMMA shell was partly dissolved with the Bis-GMA resin. After photopolymerization, liner PMMA chains interpenetrated and entangled with the dental resin network, which resulted in an in situ nano-interface in the shell structure. Improvement of the mechanical properties of the PAN–PMMA nanofiber reinforced Bis-GMA composites has been achieved through this nano-interface formation.
Co-reporter:Gang Li, Chen Zhang, Yang Wang, Peng Li, Yunhua Yu, Xiaolong Jia, Haiyang Liu, Xiaoping Yang, Zhongmin Xue, Seungkon Ryu
Composites Science and Technology 2008 Volume 68(15–16) pp:3208-3214
Publication Date(Web):December 2008
DOI:10.1016/j.compscitech.2008.08.006
Kevlar fiber was functionalized with phosphoric acid (PA) of different concentrations. The monofilament tensile strength was constant with less than 40 wt% PA functionalization. The amount of surface oxygen functional groups was maximal at 20 wt% PA-functionalized Kevlar fiber, in which the surface roughness of functionalized fiber approached to that of as-received fiber. Using optimally functionalized fiber, various combinations of epoxy and hardener were studied. The composite mechanical properties were far enhanced when 40 wt% DGEBF were added to DGEAC/DDM/DETDA system, which was attributed to interfacial adhesion between functional groups and resin matrix, and toughness matching between fiber and matrix. The interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) were 76 and 79 MPa, respectively, and the fiber strength conversion ratio of Naval Ordnance Laboratory (NOL) Rings reached 95%. Microstructure analysis revealed that better interfacial adhesion resulted in higher improvement of composite mechanical properties.
Co-reporter:Gang Li, Peng Li, Chen Zhang, Yunhua Yu, Haiyang Liu, Shen Zhang, Xiaolong Jia, Xiaoping Yang, Zhongmin Xue, Seungkon Ryu
Composites Science and Technology 2008 Volume 68(3–4) pp:987-994
Publication Date(Web):March 2008
DOI:10.1016/j.compscitech.2007.07.010
A novel approach for toughening carbon fiber/epoxy composite using electrospun polysulfone (PSF) nanofibrous membranes was performed. As-received membranes were composed of nanofibers with random orientation, and were directly electrospun onto layers of carbon fiber/epoxy prepregs to toughen the composites. According to the random dispersed nanofibers in the membranes, the inhomogeneous phase separation of polysulfone, which was generated in situ along the nanofibers direction during the curing of epoxy matrix, was proposed. Owing to the aligned PSF spheres, excellent mechanical properties of composites were obtained. Mode I interlaminar fracture toughness (GIC) increased 158%, 261% and 281% by loading 1 wt%, 3 wt% and 5 wt% nanofibrous membranes, which was far higher than those of the same content PSF films toughened composites. DMTA tests revealed good compatibility between nanofibrous membranes and epoxy matrix. And the flexural properties increased slightly compared to untoughened composite.
Co-reporter:Xiaolong Jia, Gang Li, Gang Sui, Peng Li, Yunhua Yu, Haiyang Liu, Xiaoping Yang
Materials Chemistry and Physics 2008 Volume 112(Issue 3) pp:823-830
Publication Date(Web):20 December 2008
DOI:10.1016/j.matchemphys.2008.06.048
Excellent ablative properties of ethylene–propylene–diene elastomer (EPDM) composites were obtained by adding pretreated polysulfonamide pulp (PSA-pulp). The effects of pulp pretreatment and pulp content on the mechanical and ablative properties of PSA-pulp/EPDM composites were studied. Experimental results showed that the tensile strength decreased slightly and the ablative properties increased by 3 folds on addition of 10 phr pretreated PSA-pulp. This significant improvement in the ablative properties was attributed to the enhanced dispersion degree and improved interfacial adhesion of pretreated PSA-pulp to EPDM matrix, which were observed from scanning electron microscopy. The ablation behavior of pretreated PSA-pulp/EPDM composites was proposed in accordance with the characterizations of thermogravimetric analysis (TGA), energy disperse X-ray spectroscopy (EDS) and pyrolysis-gas chromatograph–mass spectrometry (Py-GC–MS). The carbonized PSA-pulp acted as a skeleton in retaining the char layer and reduced the material loss during the high temperature ablation.
Co-reporter:Gang Li, Peng Li, Yunhua Yu, Xiaolong Jia, Shen Zhang, Xiaoping Yang, Seungkon Ryu
Materials Letters 2008 Volume 62(Issue 3) pp:511-514
Publication Date(Web):15 February 2008
DOI:10.1016/j.matlet.2007.05.080
Novel carbon fiber/epoxy composite toughened by electrospun polysulfone (PSF) nanofibers was prepared to enhance fracture toughness of the composite, and compared the morphology and toughness to those of composite toughened by PSF films prepared by solvent method. Polysulfone nanofibers with the average diameter of 230 nm were directly electrospun onto carbon fiber/epoxy prepregs to toughen the composite. SEM observations of the polysulfone nanofibers toughened composite revealed that polysulfone spheres with uneven sizes presented uniform dispersion through interleaves of the composite, which was different from those of composite toughened by PSF films. Mode I fracture toughness (GIC) of the nanofibers toughened composite was 0.869 kJ/m2 for 5.0 wt.% polysulfone nanofibers content, which was 140% and 280% higher than those of PSF films toughened and untoughened composite due to the uniform distribution of polysulfone spheres.
Co-reporter:Hongyang Cai, Peng Li, Gang Sui, Yunhua Yu, Gang Li, Xiaoping Yang, Seungkon Ryu
Thermochimica Acta 2008 Volume 473(1–2) pp:101-105
Publication Date(Web):10 July 2008
DOI:10.1016/j.tca.2008.04.012
Curing kinetics of two epoxy resin/flexible amine systems was studied by dynamic and isothermal differential scanning calorimetry (DSC). In dynamic experiments, the activation energy at different curing degree was computed under nonisothermal condition by using isoconversion method. At the same time, the isothermal experimental data was simulated by nonlinear least-squares fitting (NLSF). The results showed that the Arrhenius activation energy (E) increased with the increasing curing degree of diglycidyl ether of bisphenol A (DGEBA)–Jeffamine (T403) system, while in the DGEBA–D230 system activation energy decreased in the initial stage, and then increased when the value of α (the curing degree) was within the range of 0.1–0.4, and afterwards decreased. Under the isothermal condition, the Kamal's model was suitable to simulate two systems in the whole curing process.
Co-reporter:Weiming Chen;Peng Li;Yunhua Yu
Journal of Applied Polymer Science 2008 Volume 107( Issue 3) pp:1493-1499
Publication Date(Web):
DOI:10.1002/app.26861
Abstract
Curing kinetics of DGEAC/DDM/DETDA/DGEB epoxy resin system was studied using dynamic and isothermal differential scanning calorimetry (DSC) for the preparation of T800 carbon fiber filament wound composites. In dynamic experiment, four kinds of epoxy resin systems were studied. Curing characteristics, such as curing range and curing temperatures of the epoxy resin system with mixed hardeners (DGEAC/DDM/DETDA), were found lying within those of the two epoxy resin systems with a single hardener (DGEAC/DDM, DGEAC/DETDA). The addition of reactive diluter (DGEB) caused increase in curing range and exothermic heat. In addition, the activation energies calculated by the isoconversional method of all four resin systems decreased to the minimum value in the early stage due to the autocatalytic role of hydroxyl groups in the curing reaction and then increased due to the increased viscosity and crosslink of epoxy systems. The addition of reactive diluter led to the decrease in activation energies on the initial stage (conversion = 0.1–0.3). In isothermal experiment, a series of isothermal DSC runs provided information about the curing kinetics of the DGEAC/DDM/DETDA/DGEB system over a wide temperature range. The results showed that the isothermal kinetic reaction of the epoxy resin followed an autocatalytic kinetic mechanism. The autocatalytic kinetic expression chosen in this work was suitable to analyze the curing kinetics of this system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Peng Li;Yunhua Yu
Journal of Applied Polymer Science 2008 Volume 109( Issue 4) pp:2539-2545
Publication Date(Web):
DOI:10.1002/app.28234
Abstract
Initiators play an important role in the curing of vinyl ester resins. In this study, two kinds of initiators were used to investigate the effects of initiator systems on the cure kinetics, microstructure, and mechanical properties of vinyl ester resins. The reaction kinetics, investigated with isothermal differential scanning calorimetry (DSC), showed that the combination of different kinds of initiators could significantly decrease the induction times and exothermal peak times and increase the amount of isothermal reaction heat in comparison with a single-initiator system. The residual heat of the isothermal cure of vinyl ester resins, obtained by DSC, demonstrated the existence of microheterogeneity in the cured resins. The DSC data also showed that the highly crosslinked phase (the microgel phase) was more perfect for the resins cured with an initiator-combination system. No significant difference was observed in the mechanical properties of resins cured under different conditions, whereas the cure temperature had a great effect on the mechanical properties of cured resins. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Guoqiang Chen;Fang Mei;Xiaoyang Hu;Seungkon Ryu;Xuliang Deng;Gang Sui
Journal of Biomedical Materials Research Part A 2007 Volume 82A(Issue 2) pp:445-454
Publication Date(Web):12 FEB 2007
DOI:10.1002/jbm.a.31166
Poly-L-lactic acid (PLLA)/hydroxyapatite (HA) hybrid membranes were fabricated via electrospinning of the PLLA/HA dispersion for use in bone tissue regeneration. The structural properties and morphologies of PLLA and PLLA/HA hybrid membrane were investigated by measuring the Brunauer-Emmett-Teller specific surface area, observations of SEM, and TEM. The dispersion and integrating of HA nanoparticles in the hybrid membrane were studied by energy dispersion X-ray analysis and FTIR. The mechanical properties of PLLA/HA membrane were also measured by tensile tests. For exploring biological behaviors of the hybrid membrane, in vitro degradation tests were carried out. The osteoblast cell (MG-63) was cultured in PLLA/HA hybrid membrane extract containing medium; the cell adhesion and growth capability were investigated by SEM observation and MTT assay. HA nanoparticles were not only dispersed in the PLLA but also reacted with the functional group of PLLA, resulting in strong surface bonding and high tensile strength of hybrid membrane. The cell adhesion and growth on the PLLA/HA hybrid membrane were far better than those on the pure PLLA membrane, which proves that the PLLA/HA hybrid membrane can be one of the promising biomaterials for bone tissue regeneration. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Co-reporter:Fang Mei, Jinsheng Zhong, Xiaoping Yang, Xiangying Ouyang, Shen Zhang, Xiaoyang Hu, Qi Ma, Jigui Lu, Seungkon Ryu and Xuliang Deng
Biomacromolecules 2007 Volume 8(Issue 12) pp:
Publication Date(Web):November 19, 2007
DOI:10.1021/bm7006295
Significant effort has been devoted to fabricating various biomaterials to satisfy specific clinical requirements. In this study, we developed a new type of guided tissue regeneration (GTR) membrane by electrospinning a suspension consisting of poly(l-lactic acid), multiwalled carbon nanotubes, and hydroxyapatite (PLLA/MWNTs/HA). MWNTs/HA nanoparticles were uniformly dispersed in the membranes, and the degradation characteristics were far improved. Cytologic research revealed that the PLLA/MWNTs/HA membrane enhanced the adhesion and proliferation of periodontal ligament cells (PDLCs) by 30% and inhibited the adhesion and proliferation of gingival epithelial cells by 30% also, compared with the control group. After PDLCs were seeded into the PLLA/MWNTs/HA membrane, cell/membrane composites were implanted into the leg muscle pouches of immunodeficient mice. Histologic examinations showed that PDLCs attached on the membranes functioned well in vivo. This new type of membrane shows excellent dual biological functions and satisfied the requirement of the GTR technique successfully in spite of a monolayer structure. Compared with other GTR membranes on sale or in research, the membrane can simplify the manufacturing process, reduce the fabrication cost, and avoid possible mistakes in clinical application. Moreover, it does not need to be taken out after surgery. PLLA/MWNTs/HA membranes have shown great potential for GTR and tissue engineering.
Co-reporter:Lan Huang, Xiaoping Yang, Xiaolong Jia and Dapeng Cao
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 45) pp:
Publication Date(Web):
DOI:10.1039/C4CP03120B
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