BLENDS OF PHENOLPHTHALEIN POLY(ETHER ETHER KETONE) AND A THERMOTROPICLIQUID-CRYSTALLINE COPOLYESTER

Blends of phenolphthalein poly( ether ether ketone) ( PEX-C) and a the rmotropic liquid crystalline copolyester (LCP), poly[( 1-phenylethyl-p -phenylene terephthalate)-co-( l-cumyl-p -phenylene terephthalate)], was prepared via melt mixing. The studies of differential scanning cal orimetry (DSC) and dynamic mechanical analysis (DMA) indicate that the PEK-C/LCP blends display two glass transition temperatures which corr espond to those of PEK-C- and LCP-rich phases, respectively. The PEK-C /LCP blends were judged to be partially miscible. Scanning electron mi croscopy (SEM) was employed to examine the morphology of the blends, a nd it was observed that all the PEK-C/LCP blends displayed a phase-sep arated structure. The interface between the PEK-C- and LCP-rich phases is poor. The Young's modulus of the PEK-C/LCP blends was found to inc rease with LCP content due to the high modulus of the LCP. However, th e tensile strength and the elongation at break of the blends greatly d ecreases with increase of LCP content, owing to the poor interfacial a dhesion. From thermogravity analysis (TGA), it was observed that all t he blends exhibited a two-step weight loss mechanism, and the thermal degradation onset temperature of the blends was lowered with the addit ion of LCP content. (C) 1998 John Wiley & Sons, Inc.