Material PropertiesRheological, morphological, thermal, and mechanical properties of blends of vectra A950 and poly(trimethylene terephthalate): A study on a high-viscosity-ratio system

Poly(trimethylene terephthalate) (PTT) and a liquid crystalline polymer, Vectra A950 (VA), were melt-blended and subjected to capillary rheometry. Effects of VA content, shear rate and temperature on viscosity and flow activation energy (Ea) were investigated. Partial fibrillation was found even though the viscosity ratio was greater than one, leading to the formation of in-situ composites. Thermal and thermogravimetric analysis of the blends suggested that they were immiscible and their thermal stabilities were enhanced. From tensile tests, the incorporation of VA improved tensile modulus, slightly decreased tensile strength, and drastically lowered elongation at break, compared to neat PTT. It was found that the blend with the best VA dispersion can be achieved at the minimum VA content (10 wt%) and lowest processing temperature (250 °C). Not only did this blend exhibit improved mechanical properties comparable to those of blends processed at temperatures closer to the crystalline-to-nematic transition of VA (∼280 °C), it also shows enhanced processibility through the reduction of both melt viscosity and Ea.