Changes in Mechanical Properties of Polyethylene Telephthalate with Crystallization

The effect of the processes of crystallization, which are the annealing from the solid state and the slow cooling from the molten state, on the mechanical properties and morphology of the PET (polyethylene telephthalate) resin was examined. It was found that the increase of crystallinity due to the annealing takes place at 120°C and the crystallization due to the slow cooling takes place at 220°C. Tg and Young's modules were increased when the crystallinity of PET was increased with crystallization by the annealing or the cooling, however, there were no discrepancies of the thermal and mechanical properties. These results suggest that the improvement of the thermal and mechanical properties can be achieved by the adjustment of annealing or cooling process of the mold on the injection molding.