THE TG DISPLACEMENT MEASUREMENTS - A WAY TO FORESEE THE PHYSICAL BEHAVIOR AND THE USE OF GLASSY-POLYMERS

The effect of ageing temperature (below T(g)) on physical ageing of glassy PET has been investigated by differential scanning calorimetry. The position of the glass transition endotherm was found to be strongly dependent on the annealing conditions (time, annealing temperature). A single relaxation time model is proposed for the analysis of physical ageing. The variations of the equilibrium relaxation time tau(iso) with annealing temperature allow the determination of the parameters of the model. Finally, using these constants, one can determine the thermal past and foresee the thermal future of unknown samples which are of prime importance in processes using temperatures around the glass transition temperature.