The crystallisation of blends of syndiotactic polystyrene and polyphenylene ether

Blends of syndiotactic polystyrene (SPS) with polyphenylene ether (PPE) have been prepared to determine the effect of blending on the crystallisation mechanism of SPS. The miscibility of the blend was confirmed by both differential scanning calorimetry and dynamic mechanical thermal analysis. Crystallisation of the blends was studied under isothermal and non-isothermal conditions using differential scanning calorimetry, and the isothermal crystallisation kinetics were interpreted using the Avrami equation with the Avrami exponent, n, determined as a non-integer value varying between 2 and 3. The nucleation mode was determined as existing within regime II crystallisation, as defined by Lauritzen-Hoffman theory. Non-isothermal crystallisation kinetics were estimated using Nakamura's model. X-ray diffraction was used to determine that the SPS polymorph present was the p-form. The diffuse scattering was shown to increase with PPE content, particularly with blends prepared using higher molecular weight PPE. Overall, the results indicate that the crystallisation of SPS is affected by blending with PPE, with the melting enthalpy of SPS decreasing and the half-time to crystallisation increasing with PPE concentration. This is thought to occur because of the lack of flexibility in the PPE chain compared with the SPS chain. (C) 2000 Elsevier Science Ltd. All rights reserved.