Influence of the type of polyhydroxyether on mechanical properties of PET/TLCP/polyhydroxyether blends

In a more elaborate article, it was described that blends of poly(ethylene terephthalate) (PET), a liquid crystalline copolyester, and small amounts of a liquid crystalline polyhydroxyether showed an increase in tensile modulus and strength compared to the blends without polyhydroxyether. The results were obtained using a polyhydroxyether composed of 75 mol % biphenyl and 25 mol % phenyl units. In this article, the use of two other types of polyhydroxyether is described, one based on the alpha-methylstilbene unit and the other based on bisphenol A. Addition of either of these polyhydroxyethers to the PET/thermotropic liquid crystalline polymer (TLCP) blends increased the tensile modulus and strength of extruded fibers in a similar way as upon addition of the liquid crystalline polyhydroxyether. Improvement of the viscosity ratio and thereby improvement of the fibril formation, by reactions of the functional hydroxyl side groups in the polyhydroxyethers, appears to be the most important factor for the improvement of the mechanical properties. (C) 1999 John Wiley & Sons, Inc.