RELAXATION OF SEGMENTAL ORIENTATION AND CHAIN EXTENSION IN POLYCARBONATE STUDIED BY INFRARED DICHROISM AND SHRINKAGE

The relaxation of the segmental orientation and the chain extension in polycarbonate have been studied by infrared dichroism and heat shrink age after a step strain deformation to a draw ratio of lambda = 1.75. This makes it possible to distinguish between local relaxation mechani sms (Rouse) and large-scale relaxation mechanisms of the molecular ori entation. It was found that the average relaxation time for segmental orientation is shorter and more temperature dependent than the average relaxation time for the chain extension. The segmental orientation re laxes almost totally at 170 degrees C (T-g = 148 degrees C) before the chain extension even starts to relax.