EFFECTS OF MOLECULAR-WEIGHT AND INTERACTION PARAMETER ON THE GLASS-TRANSITION TEMPERATURE OF POLYSTYRENE MIXTURES AND ITS BLENDS WITH POLYSTYRENE POLY(2,6-DIMETHYL-P-PHENYLENE OXIDE)/

The glass transition temperature (T-g) of mixtures of polystyrene (PS) with different molecular weight and of blends of poly(2,6-dimethyl-p- phenylene oxide) (PPO) and polystyrene with different molecular weight (DMWPS) was studied by a DSC method. For the whole range of compositi on, the curves of T-g vs composition obtained by experiment were compa red with predictions from the Fox, Gordon-Taylor, Couchman and Lu-Weis s, equations. It was found that the experimental results were not in a greement with those from the Fox, Gordon-TayIor and Couchman equations for the binary mixtures of DMWPS, where the interaction parameter chi was approximately zero. However, for the blends PPO/DMWPS (chi < 0), with an increase of molecular weight of PS, it was shown that the expe rimental results fitted well with those obtained from the Couchman, Go rdon-Taylor and Fox equations, respectively. Furthermore, the Gordon-T aylor equation was nearly identical to the Lu-Weiss equation when \chi \ was not very large. Further, the dependence of the change of heat ca pacity associated with the glass transition (Delta C-p) on the molecul ar weight of PS was investigated and an empirical equation was present ed. (C) 1997 Elsevier Science Ltd.