The yield behaviour of amorphous polyethylene terephthalate: An activated rate theory approach

Yield-stress measurements on amorphous polyethylene terephthalate film are presented covering five decades of strain rate at temperatures from just below the glass transition ( 60° C) to –160° C. The data were obtained by combining measurements from a conventional Instron machine with data from a high-speed tensile tester capable of applying strain rates of up to 50 sec^–1. Five different failure modes have been identified over this extensive range of test conditions. All data from tests which show a clear yield point can be described accurately by an extension of the Ree Eyring approach to include two processes. The process which is only important at low temperatures correlates well with the-process observed in dynamic mechanical experiments.