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Characterization of molecular orientation by differential scanning calorimetry

Part 1 Tg-TLL region for amorphous polymers

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Abstract

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 forM inw/M n ≃1, and T LL/T g=1.15 ± 0.01 for ¯M wM n > 1.

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Rogers, M.G. Characterization of molecular orientation by differential scanning calorimetry. J Mater Sci 26, 4281–4284 (1991). https://doi.org/10.1007/BF00543637

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