Relation between the compression yield stress and the mechanical loss peak of bisphenol-A-polycarbonate in the β transition range

Abstract

The compression yield behaviour of polycarbonate, at constant strain-rate, over a wide range of temperatures, is described by the Ree-Eyring theory of non-Newtonian viscosity linked with a treatment which takes into account a distribution function of activation energies.

The proposed yield mechanism relies on the assumption that theβ process considered in the Ree-Eyring theory and the loss peak revealed by oscillatory measurements are related to the same molecular movements.

A relation is given between theβ transition conditions in yield measurements and in damping tests; its validity is checked.

The broadness and the shape of theβ loss peak are correlated with a spectrum of activation energies.

The compression yield-stress curve, giving the yield stress versus temperature at constant strain-rate, is computed from the measurements of the loss tangent, as a function of temperature, at the frequency corresponding to the strain-rate and is found to fit the data fairly well.