The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Toshihide Tsukatani - One of the best experts on this subject based on the ideXlab platform.
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N,N-dicyclohexylcarbodiimide assisted synthesis and characterization of poly(vinyl alcohol-co-vinyl levulinate)
Polymer, 2005Co-Authors: Yan Mei Wang, Atsushi Ikeda, Naruhito Hori, Akio Takemura, Hirokuni Ono, Tatsuhiko Yamada, Toshihide TsukataniAbstract:Abstract Poly(vinyl alcohol-co-vinyl levulinate) was synthesized by N,N-dicyclohexylcarbodiimide assisted esterification of poly(vinyl alcohol) with free levulinic acid using 4-pyrrolidino pyridine as a catalyst in N,N-dimethyl acetamide/lithium chloride solvent system in order to optimize the reaction condition. The vinyl levulinate content in the copolymer was attained up to 0.95. The 13C NMR dyad compositional analysis indicated the block character of the copolymer was 0.92, suggesting almost random poly(vinyl alcohol-co-vinyl levulinate) was formed. Glass transition temperature dependence on vinyl levulinate content of the copolymers fitted better into Gordon–Taylor Equation as compared with Fox Equation and the glass transition temperature of poly(vinyl levulinate) was given as 2.3 °C by the least regression method.
Myung S. Jhon - One of the best experts on this subject based on the ideXlab platform.
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Miscibility of biodegradable synthetic aliphatic polyester and poly(epichlorohydrin) blends
Polymer, 1999Co-Authors: Jinho Kim, Hyoung Jin Choi, Tae K. Shin, Myung S. JhonAbstract:Abstract Miscibility and thermal behavior of blends of synthetic biodegradable aliphatic polyester (BDP) with poly(epichlorohydrin) (PECH) were investigated by both differential scanning calorimetry and a dynamic mechanical thermal analyzer. Single glass transition temperatures in agreement with the Fox Equation indicate that these blend mixtures are miscible. This was further clarified from the cryogenically fractured surface of BDP–PECH blends by scanning electron microscopy.
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Polymer Communication Miscibility of biodegradable synthetic aliphatic polyester and poly(epichlorohydrin) blends
1999Co-Authors: Jinho Kim, Tae K. Shin, Hyoung J. Choi, Myung S. JhonAbstract:Miscibility and thermal behavior of blends of synthetic biodegradable aliphatic polyester (BDP) with poly(epichlorohydrin) (PECH) were investigated by both differential scanning calorimetry and a dynamic mechanical thermal analyzer. Single glass transition temperatures in agreement with the Fox Equation indicate that these blend mixtures are miscible. This was further clarified from the cryogenically fractured surface of BDP‐PECH blends by scanning electron microscopy. q 1999 Elsevier Science Ltd. All rights reserved.
Naibin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Miscibility of epoxy resins/poly(ethylene oxide) blends cured with phthalic anhydride
Polymer, 1994Co-Authors: Xiaolie Luo, Sixun Zheng, Naibin ZhangAbstract:Abstract Epoxy resins (EP)/poly(ethylene oxide) (PEO) blends cured with phthalic anhydride were studied by differential scanning calorimetry and dynamic mechanical analysis. Single glass transition temperatures were observed for all blends before and after curing, indicating a high degree of miscibility. At the same time, a marked deviation from the empirical Equation (e.g. the Fox Equation) was noticed after curing. This is ascribed to the dilution effect of the PEO component and participation of PEO in the cure reaction resulting in incomplete crosslinking, i.e. the formation of imperfect crosslinking network structures. Fourier transform infra-red spectroscopy provided strong evidence that there is a specific interaction between the EP and PEO molecules.
Ma Dezhu - One of the best experts on this subject based on the ideXlab platform.
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Epoxy resin/poly(ethylene oxide) blends cured with aromatic amine
Polymer, 1995Co-Authors: Zheng Sixun, Zhang Naibin, Luo Xiaolie, Ma DezhuAbstract:Abstract Blends of 4,4′-diaminodiphenylmethane-crosslinked diglycidyl ether of bisphenol A/poly(ethylene oxide) (PEO) were investigated. The miscibility of the blends was established on the basis of thermal analysis and dynamic mechanical analysis studies. A single, composition-dependent glass transition temperature ( T g ) was seen, and a marked negative deviation from the Fox Equation was noticed after the curing reaction. The more PEO content in the blends, the larger is the negative deviation. This is ascribed to the formation of imperfect semi-interpenetrating polymer networks of epoxy/PEO, since the dilution effect of PEO, which is a miscible, inactive diluent, results in an incomplete curing reaction. Therefore, T g values decrease.
Manuel Hidalgo - One of the best experts on this subject based on the ideXlab platform.
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Influence of the physical characteristics of the polymer on the glass transition of various chemically modified PVCs
Journal of Polymer Science Part A: Polymer Chemistry, 1995Co-Authors: Manuel Hidalgo, Carmen MijangosAbstract:Vinylchloride-vinylthiocresol and vinylchloride-vinylthionaphthol copolymers of various compositions were prepared by the substitution reaction of PVC with sodium thiocresol and sodium thionaphthol, respectively, in different solvents and at different temperatures. The variation of the glass transition temperature of these copolymers with chemical composition does not follow the Flory-Fox Equation, but is found to depend on the solvent and the temperature at which the copolymer is obtained. The comonomer sequence distribution and stereosequence content of the above copolymers, and those of vinylchloride-vinylthiobenzene copolymer, were determined by 1 H- and 13 C-NMR spectroscopy. The dependence of comonomer distribution and stereoregularity content with chemical composition for the three series of copolymers, prepared in different solvents and temperatures, are similar. The T g deviations for the three series of copolymers were attributed to the contribution of physical characteristics of the PVC structure, originating from polymer-solvent interactions.
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Influence of the reaction medium and the reactant on the glass transition temperature of chemically modified poly(vinyl chloride)
Polymer, 1994Co-Authors: Carmen Mijangos, Manuel HidalgoAbstract:Abstract Copolymers based on substituted poly(vinyl chloride) (PVC) produced by reacting PVC with different thiolates in cyclohexanone solution and in the absence of solvent (melt), show different glass transition temperatures, Tg, for the same chemical composition. The variation of Tg for the vinylchloride-vinylthiobenzene, vinylchloride-vinylthiocresol and vinylchloride-vinylthionaphthol copolymers obtained in the melt follows the Fox Equation. However, the same copolymers obtained in cyclohexanone show a deviation from this trend of Tg as a function of molar composition. Factors such as microstructure, chemical composition distribution and molecular weight do not change appreciably from solution to the melt, and therefore cannot be responsible for these differences in the Tg values. We attribute the deviation in the Tg values of copolymers obtained in cyclohexanone solution to polymer-polymer interactions produced at local sites on the chain, and we propose that these interactions are related to chlorine atoms in isotactic and/or heterotactic triads.
