The crystallisation of blends of syndiotactic polystyrene and polyphenylene ether

Blends of syndiotactic polystyrene (SPS) with polyphenylene ether (PPE) hav e been prepared to determine the effect of blending on the crystallisation mechanism of SPS. The miscibility of the blend was confirmed by both differ ential scanning calorimetry and dynamic mechanical thermal analysis. Crysta llisation of the blends was studied under isothermal and non-isothermal con ditions using differential scanning calorimetry, and the isothermal crystal lisation kinetics were interpreted using the Avrami equation with the Avram i exponent, n, determined as a non-integer value varying between 2 and 3. T he nucleation mode was determined as existing within regime II crystallisat ion, 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 sc attering was shown to increase with PPE content, particularly with blends p repared using higher molecular weight PPE. Overall, the results indicate th at the crystallisation of SPS is affected by blending with PPE, with the me lting enthalpy of SPS decreasing and the half-time to crystallisation incre asing 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 Elsev ier Science Ltd. All rights reserved.