Effect of thermal history on the tensile yield stress of polycarbonate in the β transition range

Abstract

The tensile yield behaviour of three forms of polycarbonate differing in their thermal history is investigated, at constant strain rate, over a wide range of temperatures (−140° to + 80°C). The plot of the yield stress versus temperature exhibits a thermal history dependence over the whole range explored and reveals the β transition which is located at the same temperature T β for the three forms. The yield behaviour is described assuming that two activated processes α and β requiring additive stresses are involved. The β component of the yield stress is found to be insensitive to thermal history as well as the related loss peak. Only the α process is affected; details concerning this dependence are discussed.