PHYSICAL AGING OF ISOTROPIC AND ANISOTROPIC POLYCARBONATE

Polycarbonate displays physical ageing when subjected to annealing in the glassy state. The ageing is considerably enhanced with oriented polycarbonate, particularly if the orientation is achieved by cold drawing. The effect of cold drawing and annealing on mobility and free volume has been investigated by means of electron spin resonance spectroscopy using the spin probe method as well as by dilatometric and X-ray scattering studies. The experimental results show that the mean rotational correlation times of the probes and the correlation time distribution depend on the mechanical and thermal history of the sample. The mobility changes are correlated with results of X-ray scattering and dilatometry and interpreted in terms of changes in the magnitude of the free volume and its distribution. © 1990.