Cold‐drawing (necking) behavior of polycarbonate as a double glass transition

The thermomechanical behavior of poly(bisphenol A carbonate) (PC) undergoing cold‐drawing (necking) over a large range of temperature and strain rate has been studied. The cold‐drawing of PC has been described from a material particle perspective in terms of true stress and strain relationships. The isothermal draw stress is shown to be a material parameter, and the true stress‐strain behavior of necked material above the true drawing stress follows conventional treatment by rubber elasticity. Cold‐drawing is described as a double glass transition: first, a transition from an isotropic glass to an isotropic rubber at the yield point, then, on unloading after stretching of a rubbery mesophase, a transition from an oriented rubber to an oriented glass.