LIQUID-CRYSTALLINE POLYMER AS A PROCESSING AGENT IN BLENDS OF POLY(ETHER-KETONE) LCP70/

Blends of a liquid crystalline thermotropic copolyester (LCP70) and an amorphous phenolphthalein based poly(ether-ketone)(PEK-C) with two vi scosities were prepared by melt blending. The blends' morphology, rheo logical and mechanical properties were investigated by DSC, SEM, mecha nical and rheological tests. It was observed that the optimum composit ion of the PEK-C/LCP70 blend was 10 wt% LCP for both mechanical and rh eological properties. When the LCP content was less than 10%, the LCP phase existed as finely dispersed fibrous domains with a diameter of a bout 1 mu m in the matrix, and both tensile and flexural properties we re improved. In contrast, when the LCP content reached 20% or more, th e LCP domains coalesced to ellipsoidal particles with a diameter of ab out 5 mu m, and the mechanical properties decreased as a result. It is demonstrated that pure PEK-C with a high viscosity which was difficul t to process by melt extrusion, could be extruded conveniently when 10 % LCP70 was incorporated. It is emphasized that LCP not only can be us ed as a reinforcing phase but also an effective processing agent for e ngineering thermoplastics, especially for those with high viscosity an d narrow processing window. (C) 1997 Elsevier Science Ltd.