Showing papers by "Kung-Hwa Wei published in 1997"
TL;DR: In this article, the transesterification mechanisms and rate in blends of polycarbonate (PC) and random liquid crystalline polyester copoly (oxybenzoate-p-terephthalate) at molar ratio 40/60 (P46) were studied through a five-component diad analysis and with 13C and 1H-13C nuclear magnetic resonance spectroscopy.
Abstract: Transesterification mechanisms and rate in blends of polycarbonate (PC) and random liquid crystalline polyester copoly(oxybenzoate-p-terephthalate) at molar ratio 40/60 (P46) were studied through a five-component diad analysis and with 13C and 1H-13C nuclear magnetic resonance spectroscopy. It was found that the ester-ester interchange in the two polymers took place within 15 min when the blend was annealed at 260 °C in vacuum. In the annealed blend, the Bisphenol A unit in polycarbonate reacted first with the terephthalate unit and then with the oxybenzoate unit in copoly(oxybenzoate-p- terephthalate). As the transesterification in the blend continued for about 1 h, the forming of diad Bisphenol A-oxybenzoate exceeded that of diad Bisphenol A-terephthalate. This large loss (57%) of the diad oxybenzoate-oxybenzoate caused the disappearance of the liquid crystalline phase in the blend. In sharp contrast to the originally immiscible blend of PC and P46 (two distinctive glass transition temperatures), the large loss of the liquid crystalline diad resulted in complete miscibility in the annealed blend, as evidenced by the appearance of a single glass transition temperature in the differential scanning calorimetry measurement.
51 citations
TL;DR: In this article, the mixture of liquid crystalline poly(p-oxybenzoate-co-p-phenyleneisophthalate) (HIQ) and polycarbonate (PC) was investigated with differential scanning calorimetry.
20 citations
TL;DR: In this paper, a compatibilized version of the Vectra A950 and polycarbonate (PC) was used to increase tensile modulus and tensile strength.
Abstract: Blends of liquid crystalline poly(oxybenzoate-co-oxynaphthalate) (Vectra A950) and polycarbonate (PC) were prepared by adding a compatibilizer to the two polymers in a melt-blending process. The compatibilizer was based on controlled transesterification between synthesized poly(oxybenzoate-co-terephthalate) (40/60) and PC. The compatibilizer exhibited birefringence, and its thermal property was analyzed by differential scanning calorimetry. The maximum increase in tensile modulus and tensile strength of these compatibilized Vectra blends were 24% and 54%, respectively, as compared with those of binary Vectra blend without compatibilizer resulting from an injection-molding process. The tensile properties of the compatibilized Vectra blends decreased once the concentration of the compatibilizer exceeded 2 phr.
18 citations