THERMAL-ANALYSIS STUDY OF THE EFFECT OF MOLECULAR-WEIGHT ON CONSTRAINED AMORPHOUS PHASE IN POLY(PHENYLENE SULFIDE)

We report a thermal analysis study of the effect of molecular weight o n the amorphous phase structure of poly(phenylene sulfide), PPS, cryst allized at temperatures just above the glass transition temperature. T hermal properties of Fortron PPS, having viscosity average molecular w eights of 30000 to 91000, were characterized using temperature modulat ed differential scanning calorimetry (MDSC). We find that while crysta llinity varies little with molecular weight, the heat capacity increme nt at the glass transition decreases as molecular weight decreases. Th is leads to a smaller liquid-like amorphous phase, and a larger rigid amorphous fraction, in the lower molecular weight PPS. For all molecul ar weights, constrained Fraction decreases as the scan rate decreases.