Abstract
The low temperature crystallization of polyethylene terephthalate (PET) under the ultrasonic irradiation was studied by the density gradient tube method, DSC and X-ray technique, and the crystallization behavior was compared with that of PET on annealing. The results obtained are as follows:
1. The influence of ultrasonic irradiation on crystallization rate depended on the temperature. Ultrasonic irradiation accelerated the crystallization of PET at temperatures of about 80°C to 125°C. This crystallization behavior of PET can be described in terms of the rate of segmental motion. Long segment moves easily in the ultrasonic field, as the potential barrier to rotation of bonds is lowerd. Additional X-ray and DSC data also support the above result.
2. The value of the Avrami exponent n, for the crystallization of PET under the ultrasonic irradiation at 100°C-102.5°C was 2.9-3.1 and n for the crystallization of PET on annealing at 105°C-110°C was 1.8-2.3.
3. In the similar manner, ultrasonic irradiation accelerated the solid-state crystallization of oriented amorphous PET.
