AMORPHOUS ORIENTATION AND INDUCED CRYSTALLIZATION IN UNIAXIALLY STRETCHED POLY(ETHYLENE-TEREPHTHALATE GLYCOL)

The degree of crystallinity of poly(ethylene terephthalate glycol) (PET) obtained by induced crystallization during stretching of amorphous PET films is related to the amorphous orientation of the samples. The results show the existence of a critical amorphous orientation for the beginning of crystallization. This critical orientation depends on the temperature of stretching but not on the strain rate. It is also shown that, during stretching, the crystallinity of PET is completely determined by the temperature and the level of amorphous orientation in the sample, and it increases with both parameters.