Relation between free volume and the low-temperature “beta” transition in glassy polycarbonate

Abstract

The addition of plasticizer or antiplasticizer to polycarbonate has been reported to cause specific volume decreases. Also antiplasticizer has been reported to suppress the “beta” transition in polycarbonate. In order to study the relation between free volume and the beta molecular motion as well as the effect of these variables on mechanical properties we have examined polycarbonate films containing various amounts of plasticizer (dibutyl phthalate) or antiplasticizer (Arochlor 5442). Specific volume, dynamic mechanical, and tensile measurements were obtained. Results showed that 10-% dibutyl phthalate and 30-% Arochlor 5442 suppress almost completely the low-temperature “beta” transition with a corresponding fractional volume loss of 0.015 at 25°C for both mixtures. Tensile measurements indicate 10-% dibutyl phthalate increases tesile yield strength whereas 30-% Arochlor 5442 increases both modulus and yield strength. Results are discussed in terms of current free volume concepts. © 1973, The Society of Polymer Science, Japan. All rights reserved.