Co-reporter:Peng Wei, Miko Cakmak, Yuwei Chen, Xinhang Wang, Yanping Wang, Yimin Wang
Thermochimica Acta 2014 Volume 586() pp:45-51
Publication Date(Web):20 June 2014
DOI:10.1016/j.tca.2014.04.008
•The thermotropic liquid crystal polyesters P-BPAFx containing BPAF unit were synthesized and characterized.•P-BPAFx shows lower melting temperature and higher glass transition temperature when compared with parent polyester P-HBA70.•The thermal stability of P-BPAFx was evaluated by Kissinger and Kissinger-Akahira-Sunose (KAS) methods.•The P-BPAF 2.5 showed better thermal stability than that of P-HBA70, higher char yield is observed for all polyesters containing BPAF unit.In this study, a series of thermotropic liquid crystal copolyesters P-BPAFx modified with 2.5–10 mol% of bisphenol AF (BPAF) and terephthalic acid (TA) were synthesized via melt polymerization. The structure and properties of P-BPAFx were characterized by various measurements. The melting temperature decreased from 260 to 220 °C and glass transition temperature increased from 70 to 118 °C after introduction of BPAF and TA units, showing P-BPAFx can easily be processed in a lower temperature and have a more broad application temperature. The thermal degradation behavior was evaluated by SEM, FTIR and thermogravimetric analysis (TG). The activation energy was obtained from Kissinger and Kissinger-Akahira-Sunose (KAS) methods, and was investigated comparatively with P-HBA70. It was found that the addition of 2.5 mol% BPAF units improve thermal stability, and much higher char yield was observed for those copolyesters containing BPAF unit.
Co-reporter:Peng Wei;Miko Cakmak;Yuwei Chen;Xinhang Wang;Yanping Wang;Yimin Wang
Journal of Applied Polymer Science 2014 Volume 131( Issue 13) pp:
Publication Date(Web):
DOI:10.1002/app.40487
ABSTRACT
In this study, a series of aromatic copolyesters P-BPAx with lower melting temperature and higher glass transition temperature derived from hydroxybenzoic acid (HBA), 6-hydroxy-2-naphthoic acid (HNA), bisphenol A (BPA) and terephthalic acid (TA) were synthesized via melt polymerization. The copolyesters were characterized by FTIR, solid state 13C NMR, DSC, TGA, polarized optical microscopy, X-ray diffraction, and rheometry measurements. With addition of BPA, the resulting copolyester's melting temperature decreased from 260 to 221°C and its glass transition temperature increased from 70 to 135°C, compared with the parent copolyester P-HBA70 (HBA/HNA copolymer). With exception of copolyester P-BPA5.0 (225–280°C), the copolyesters could maintain liquid crystalline behavior in a broad temperature range from 230°C to higher than 410°C. The ability to form nematic liquid crystalline phase disappeared when BPA concentration became higher than 15 mol %. X-ray diffraction analysis showed crystallinity decreased as the BPA content increased. A slightly distorted O" and a substantially distorted O′ orthorhombic phase was observed for P-BPA2.5. Upon annealing at 220°C, the O" phase disappeared and the O′ phase became stronger gradually. Rheology study data showed the ability to process the copolyesters improved in those compositions containing <2.5 mol % BPA. Continuing to increase concentrations of BPA, they became intractable. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40487.
Co-reporter:Xinhang Wang;Yumin Xia;Peng Wei;Yuwei Chen;Yanping Wang ;Yimin Wang
Journal of Applied Polymer Science 2014 Volume 131( Issue 19) pp:
Publication Date(Web):
DOI:10.1002/app.40832
ABSTRACT
Cellulose nanocrystals (CNCs) organogels were first produced from aqueous dispersion through solvent exchange of CNCs to acetone via a simple sol-gel process. After mixing the organogels with poly(propylene carbonate) (PPC) in dimethylformamide followed by solution casting, green nanocomposites were obtained with CNCs well dispersed in PPC polymer matrix which was confirmed by scanning electron microscopy observations. Differential scanning calorimeter analysis revealed that glass transition temperature of the nanocomposites was slightly increased from 34.0 to 37.4°C. Tensile tests indicated that both yield strength and Young's modulus of CNCs/PPC nanocomposites were doubled by adding 10 wt % CNCs. However, poor thermal stability of PPC occurred after incorporating with CNCs due to the thermo-sensitive sulfate groups located on the surface of CNCs. Furthermore, PPC became more hydrophilic because of the inclusion of CNCs according to the water contact angle measurement. The enhanced mechanical and hydrophilic properties, coupled with the inherent superior biocompatibility and degradability, offered CNCs/PPC composites potential application in biomedical fields. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40832.
Co-reporter:Haroon A. M. Saeed;Yassir A. Eltahir;Yumin Xia;Wang Yimin
Polymer Bulletin 2014 Volume 71( Issue 3) pp:595-612
Publication Date(Web):2014 March
DOI:10.1007/s00289-013-1080-3
The non-isothermal crystallization of pure recycled polyethylene terephthalate (RPET) and its blends with 3 and 5 wt% hyperbranched polyester (HBPET) were investigated by differential scanning calorimetry (DSC). The DSC curves demonstrate that the melt-crystallization temperatures of the blends are always higher than that of pure RPET regardless of the cooling rate. Their non-isothermal crystallization kinetics was further analyzed with modified Avrami equation, Ozawa equation and Mo method. The analysis reveals that the crystallization half-time (t1/2) of the blends is shorter than pure RPET. The activation energy of crystallization of RPET was also determined according to Kissinger method and it is found to decrease remarkably in RPET-3 and RPET-5 blends. All the results indicate that HBPET serves as an effective nucleating agent for RPET.
Co-reporter:Haroon A. M. Saeed;Yassir A. Eltahir;Yumin Xia
Russian Journal of Applied Chemistry 2014 Volume 87( Issue 10) pp:1481-1488
Publication Date(Web):2014 October
DOI:10.1134/S1070427214100140
Carboxyl-terminated, water soluble, hyperbranched polyesters (HBPET) with aliphatic-aromatic structure were synthesized at three different monomer mole ratios (A3/B3 = 1: 1, 2: 1, 1: 2, respectively) by melt polycondensation of aconitic acid and phloroglucinol via A3+ B3 approach. Fourier transform infrared (FTIR) spectroscopy indicated as that was expected HBPET, which showed excellent solubility in a variety of polar solvents such as N,N-dimethyl formamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), and tetrahydrofuran (THF). The weight-average molecular weight of HBPET ranged from 7792 to 9214 g mol−1 and their intrinsic viscosity were varied from 0.17 to 0.34 dL g−1. The degree of branching of the HBPET was estimated to be 0.44–0.49 by 1H and 13C NMR measurement. The thermogravimetric analysis (TGA) measurement revealed that HBPET was of 10% weight-loss at 340°C in N2.
Co-reporter:Yumin Xia;Jia Wang;Su Xu;Qian Liao;Xinyuan Zhu;Yanping Wang;Yimin Wang
Journal of Applied Polymer Science 2013 Volume 127( Issue 4) pp:3249-3255
Publication Date(Web):
DOI:10.1002/app.37743
Abstract
Dually stimuli-responsive hyperbranched polyethylenimine derivatives (HPEI-star-PPOs) were successfully synthesized through Michael addition of commercial HPEI, poly(propylene oxide) dimethacrylate, and 2-mercaptoethanol. In aqueous solution, these HPEI-star-PPOs exhibited response to temperature and pH. The corresponding lower critical solution temperature (LCST) could be readily adjusted by changing the feed ratio of HPEI to PPO, which also presents the ratio of hydrophilicity to hydrophobicity, indicating that this LCST transition is based on hydrophilic–hydrophobic balance. Because of the tertiary amine as well as unreacted primary or secondary amine that can be protonated during pH decreases, HPEI-star-PPOs exhibited a pH-dependent thermoresponse. The 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay against COS-7 cells demonstrated that HPEI-star-PPO had relatively low cytotoxicity compared to HPEI. All these characteristic suggest that this stimuli-responsive polymer is a promising functional material for biomedical applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Haroon A. M. Saeed;Yimin Wang
Russian Journal of Applied Chemistry 2013 Volume 86( Issue 10) pp:1569-1575
Publication Date(Web):2013 October
DOI:10.1134/S1070427213100157
New types of carboxyl-terminated hyperbranched polyesters (HBPEs) with aromatic-aliphatic structure were synthesized by single step-melt polycondensation of adipic acid (as A2 monomer) and phloroglucinol (as B3 monomer) as a core via A2 + B3 approach, at three different monomer mole ratios (A2/B3 = 1: 1, 1.5: 1, 2: 1, respectively). FTIR spectroscopy indicated that the polymers contained hydroxyl groups, ester bonds, benzene ring, methyl and methylene groups, which were in agreement with the expected HBPEs. The HBPEs have inherent viscosities about 0.24 to 0.27 dL/g. The degree of branching of the HBPEs was estimated to be 0.45–0.49% by 1H-NMR and 13C-NMR measurements. The melting temperature of HBPE-1, HBPE-2 and HBPE-3 were 154, 155 and 160°C respectively measured by differential scanning calorimetry (DSC). The synthesized polymers were thermally stable; the thermogravimetric analysis (TGA) measurement revealed that HBPEs had 10% weight loss at 310°C in nitrogen.
Co-reporter:Yumin Xia;Yimin Wang;Yanping Wang;Dali Wang;Hongping Deng;Yuanyuan Zhuang;Deyue Yan;Bangshang Zhu;Xinyuan Zhu
Macromolecular Chemistry and Physics 2011 Volume 212( Issue 10) pp:1056-1062
Publication Date(Web):
DOI:10.1002/macp.201100077
Co-reporter:Yumin Xia, Yimin Wang, Yanping Wang, Chunlai Tu, Feng Qiu, Lijuan Zhu, Yue Su, Deyue Yan, Bangshang Zhu, Xinyuan Zhu
Colloids and Surfaces B: Biointerfaces 2011 Volume 88(Issue 2) pp:674-681
Publication Date(Web):1 December 2011
DOI:10.1016/j.colsurfb.2011.07.059
To realize the pH-targeting delivery of antitumor drug cis-dichlorodiammineplatinum(II) (cisplatin, CDDP), a tumor pH-responsive polymer-platinum(II) complex (Suc-HPMHO–CDDP) from carboxyl-modified hyperbranched polyether (Suc-HPMHO) and cisplatin was designed and prepared. Because of the existence of hydrophobic core and ionization of surface carboxylic acid, Suc-HPMHO showed reversible pH-response in aqueous solution, and its responding pH value could be readily adjusted by only changing the degree of carboxylation of Suc-HPMHO. With plenty of terminal carboxyl groups, Suc-HPMHO could form the complex with CDDP by substituting the chloride ions with carboxyls. Methyl tetrazolium (MTT) assay showed that Suc-HPMHO had low cytotoxicity, while Suc-HPMHO–CDDP complex presented a similar antitumor effect with the free CDDP. Under the tumor acidic pH (pHe), Suc-HPMHO–CDDP complex deposited around/in cells because of its pH-response. Therefore, the pH-targeting of Suc-HPMHO–CDDP complex to tumor tissue could be realized. All of these results show that the tumor pH-responsive Suc-HPMHO–CDDP complex is a potential pH-targeting drug delivery system in cancer therapy.Graphical abstractHighlights► Carboxyl-modified hyperbranched polyether was complexed with cisplatin. ► The complex showed pH-responsive behavior. ► The pH-targeting of complex to tumor tissue exhibited an efficient anticancer effect.
Co-reporter:Shujia Liu, Jia Wang, Yanping Wang, Yimin Wang
Materials & Design (1980-2015) 2010 Volume 31(Issue 4) pp:1711-1715
Publication Date(Web):April 2010
DOI:10.1016/j.matdes.2009.01.044
A new method was proposed to improve ballistic impact performance of unidirectional ultra high molecular weight polyethylene (UHMWPE) fiber plate (UD plate) by adding shell particles in matrix. The complex micro-laminate structure of these bio-composite materials was studied. It was revealed by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR) spectra that modified shell particles were uniformly dispersed in the matrix. The results of ballistic tests and temperature adaptation tests demonstrated that the bulletproof property of the modified UD plate was improved by 20%.
Co-reporter:Haifeng Wang, Wenjue Han, Yimin Wang
Journal of Non-Crystalline Solids 2008 Volume 354(12–13) pp:1146-1150
Publication Date(Web):15 February 2008
DOI:10.1016/j.jnoncrysol.2006.11.054
The surface morphology and K+, Na+ concentration distributions of plate glass were investigated by atomic force microscope (AFM) and electron probe microanalyzer (EPMA) before and after ion exchange. The AFM images indicate that the surface microcrack of chemical strengthened glass can be closed to a certain extent and the surface smoothness can be improved. The EPMA results indicate that the relationship between the weight gain and time, temperature follows Fick’s law, which are same as that of the thickness of ion exchanged layer, the total exchanged amount. Consequently, a simple and accurate weighing method was first proposed to estimate the ion exchange state.
Co-reporter:Jiangjiang Zhu, Xinying Wang, Linfeng Guo, Yimin Wang, Yanping Wang, Mingfang Yu, Kin-tak Lau
Carbon 2007 Volume 45(Issue 13) pp:2547-2550
Publication Date(Web):November 2007
DOI:10.1016/j.carbon.2007.08.019
Graphite foam was obtained after carbonization and graphitization of a pitch foam formed by the pyrolysis of coal tar based mesophase pitch mixed with graphite particles in a high pressure and temperature chamber. The graphite foam possessed high mechanical strength and exceptional thermal conductivity after adding the graphite particles. Experimental results showed that the thermal conductivity of modified graphite foam reached 110 W/m K, and its compressive strength increased from 3.7 MPa to 12.5 MPa with the addition of 5 wt% graphite particles. Through the microscopic observation, it was also found that fewer micro-cracks were formed in the cell wall of the modified foam as compared with pure graphite foam. The graphitization degree of modified foam reached 84.9% and the ligament of graphite foam exhibited high alignment after carbonization at 1200 °C for 3 h and graphitization at 3000 °C for 10 min.
Co-reporter:Yimin Wang, Junpeng Gao, Yunqian Ma, Uday S. Agarwal
Composites Part B: Engineering 2006 Volume 37(Issue 6) pp:399-407
Publication Date(Web):2006
DOI:10.1016/j.compositesb.2006.02.014
PET/montmorillonite (MMT) nanocomposites were prepared via melt-blending and its nano-dispersion morphology was confirmed by X-ray diffraction and transmission electron microscopy. Its non-isothermal crystallization behavior was studied by DSC. It is found that the crystallization rate of PET nanocomposite was increased significantly. The Avrami equation parameters related to crystallization, such as n, Zc and t1/2, were calculated and analyzed. The thermal property and mechanical property of the composite were studied. When the MMT content was 1%, the composite has a desired comprehensive property. At this composition, the thermal degradation onset temperature and the thermal deformation temperature of PET were increased by 12 and 35 °C, respectively, and the tensile strength of the PET was increased by 25% with slightly increase of the notched impact strength.
Co-reporter:Yanping Wang, Ruiling Cheng, Linli Liang, Yimin Wang
Composites Science and Technology 2005 Volume 65(Issue 5) pp:793-797
Publication Date(Web):April 2005
DOI:10.1016/j.compscitech.2004.10.012
The ultra-high molecular weight polyethylene (UHMWPE)–carbon nanotubes (CNTs) composite fibers were prepared by gel spinning. To realize the homogeneous dispersion and good load transfer between the CNTs and the polymer matrix, the purification and functionalization of CNTs were carried out. TEM, SEM, XRD, IR were used to characterize the CNTs, their dispersion in the matrix and the functional group changes on the surface of the CNTs. The results showed that there was no obvious agglomerating of CNTs in obtained composite fibers and consequently a good interaction between CNTs and UHMWPE matrix was also established. Furthermore, it was found that the adding of CNTs resulted into a peculiar structure, a more regular alignment of the UHMWPE morphology. The mechanical and thermal properties of UHMWPE–CNTs fibers prepared by gel spinning and ultra drawing were improved compared with that of pure UHMWPE fiber.
Co-reporter:Haifeng Wang, Wenjue Han, Haibing Tian, Yimin Wang
Materials Letters 2005 Volume 59(Issue 1) pp:94-99
Publication Date(Web):January 2005
DOI:10.1016/j.matlet.2004.09.024
A sealing composites were prepared by mixing superfine glass powder and epoxy resin. The effect of active agent (stearate) on glass powder size and size distribution and the effect of surface treatment of the glass powder on the microstructure and the mechanical properties of glass powder/epoxy composites were investigated. Glass powder size was measured using a laser particle size analyzer. The composite structure and property were investigated by means of SEM, material testing machine and thermo-gravimetric analysis (TGA). The results show that the adding of appropriate active agent during the grind process can reduce the glass powder size and size distribution. The results also show that the composite mechanical properties and thermostability are greatly improved by surface treatment of glass powder.
