Crazing by disentanglement: non-diffusive reptation

A molecular model of disentanglement below the glass transition temperature is applied to the crazing behaviour of polymers, such as polyethersulphone and polycarbonate, in which the molecules exhibit non-diffusive reptation. For the case when chain scission is not important, molecular weight dependences of the crazing stress, flow stress and surface energy are calculated and compared with experimental results. The model provides an explanation of the observed absence of any effect of ageing on crazing, in contrast to its effect on shear deformation.