Generation of fibrillar morphology in blends of block copolyetheresteramide and liquid crystal polyester

Polymer blends comprising liquid crystal polymers, LCP, as a minor component can be formed into fibrillar-type morphology. This morphology enables the generation of improved mechanical properties in the draw direction, in a manner comparable to unidirectional composites. In this paper, the results obtained for blends of a polyetheresteramide block copolymer, PEBA, with a liquid crystalline copolyester are presented. Films prepared using a single-screw extruder were melt drawn on calendering rolls. The blends' storage modulus increased with draw ratio, lambda, reaching a maximum value for lambda = 3-4. The storage modulus of blends containing 30 wt% LCP, and drawn to lambda = 4 to 12, was found to increase nearly 50-fold in comparison to neat PEBA (from 18 MPa to almost 1 GPa). The blends' morphology was characterized by dissolving the PEBA matrix, followed by gravimetric and microscopic analysis of the LCP phase. As expected, the average fiber diameter decreased as a function of lambda(-0.5). The fiber content as a function of h followed a trend parallel to that of the modulus. Longitudinal and transverse moduli followed the Halpin-Tsai predictions for unidirectional composites. Properties of compression molded specimens prepared from these blends compared favorably with glass fiber composites.