THE EFFECT OF MISCIBILITY ON THE MORPHOLOGY AND PROPERTIES OF BLENDS OF POLY(ETHER IMIDE) WITH LIQUID-CRYSTALLINE POLYMERS

A poly(ether imide) (Ultem), which is an amorphous engineering thermop lastic, was melt blended with two liquid crystalline polymers: one bas ed on p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid (Vectra A90 0) and the other based on phenylhydroquinone, ethylphenylhydroquinone and terephthalic acid (Granlar). The miscibility of these two blend sy stems was studied by means of differential scanning calorimetry (d.s.c .), dynamic mechanical thermal analysis (d.m.t.a.), scanning electron microscopy (s.e.m.) and wide-angle X-ray scattering (WAXS). It was fou nd that the Ultem/Vectra system is immiscible, while the Ultem/Granlar system is partially miscible. As revealed by d.m.t.a., the partial mi scibility of the latter can be improved by increasing the degree of mi xing in a single-screw extruder. The flexural and tensile moduli of th e in situ reinforced composites based on these two blend systems were determined as a function of blend composition. For similar mixing cond itions it was found that the flexural moduli of the Ultem/Granlar syst em showed a positive deviation from the simple rule of mixtures while those of the Ultem/Vectra system showed a negative deviation. The tens ile moduli of the Ultem/Vectra system also showed a pronounced positiv e deviation only for blends with high Vectra compositions. These resul ts are interpreted in terms of the differences in miscibility.