Phase Structure and Mechanical Properties of Blends of Poly(ether imide) and Bisphenol A Polycarbonate

Abstract

Poly(ether imide) (PEI)/bisphenol A polycarbonate (PC) blends were obtained throughout the composition range both by direct injection moulding (DI blends) and by extrusion followed by injection moulding (PM blends). Although some reaction was observed by FT IR, the blends were fully phase separated at the detection level of DMTA. An anomalous decrease in the high temperature Tg of the 90/10 and 80/20 blends, was only seen in PM blends. This was attributed to an anomalous thermodynamic behaviour, after rejecting degradation, reactions or particle size as possible explanations. With the exception of the PC-rich DI blends, the morphology was fine and homogeneous. Both the modulus of elasticity and the yield stress were very close to those expected from the rule of mixtures, whatever the morphology. Unexpectedly, ductility followed the same trend, even in the less homogeneous PC-rich DI blends. This points to the very slight reactions observed, and to parameters related to chemical features of the components (such as the highly aromatic character of the components of the blend) as the main reasons for the observed ductility behaviour.