Origin of Impact Strength in Polycarbonate: II. Effect of Thermal Treatments

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Abstract
The effect of thermal treatments on free volume, molecular motion and morphology of glassy polycarbonate has been studied in order to understand how these variables might be related to impact strength. Results indicate that quenching or annealing below T g produce only slight changes in specific volume or the low temperature beta transition. Significant changes in morphology are observed in polycarbonate after annealing. The previously suggested correlations between impact strength and free volume or the beta transition are difficult to understand in view of the slight changes in these variables after extensive annealing below Tg . It appears that a better correlation may exist between impact strength and the intermediate transition (between alpha and beta) and the size of the nodular structure in the glass.