Phase behaviour, morphology and properties of poly(ether imide)/polyarylate blends

Poly(ether imide) (PEI)/polyarylate (PAr) blends of different compositions were obtained by melt blending followed by compression moulding. 90/10 and 80/20 blends appeared miscible by both differential scanning calorimetry and dynamic mechanical thermal analysis. The other compositions were biphasic; one phase was almost pure PAr and the other PEI with a fairly constant PAr content of roughly 25%. This phase behaviour agreed with both the observed transparency and the fracture surfaces observed by scanning electron microscopy. The mechanical properties of the blends as a function of composition showed values close to linearity or were even enhanced, with an unexpected synergism in ductility. This behaviour and that observed in other polymer blends, suggest that, assuming isotropy and constant crystallinity content, the relation between increased miscibility level and improved ductility is not a general rule. (C) 1996 Elsevier Science Ltd.