CHARACTERIZATION OF MOLECULAR-ORIENTATION BY DIFFERENTIAL SCANNING CALORIMETRY .1. TG-TLL REGION FOR AMORPHOUS POLYMERS

Differential scanning calorimetry was used to study relaxations occurring above the glass transition, T(g) for a number of characterized and fabricated polystyrenes. Part 1 of this study examines the liquid liquid relaxation temperature, T(LL); Part 2 the effects of injection moulding and biaxial orientation of polystyrene; and Part 3 deals with the effects of injection blow moulding. The rubbery plateau region was found to be bounded by the glass transition, T(g), and a weak transition or relaxation, T(LL), found above T(g) as an endothermic slope change in the base line. In some cases, this transition could be enhanced as a step change when molten samples were quenched in liquid nitrogen. The effect of molecular weight on T(g) and T(LL) was similar, and had the relationships T(LL)/T(g) = 1.07 + 0.03 for MBAR(w)/MBAR(n) congruent-to 1, and T(LL)/T(g) = 1.15 +/- 0.01 for MBAR(w)/MBAR(n) > 1.