Conventional PET is a crystalline polymer. After biaxial stretching and orientation, PET film exhibits a significant degree of crystallinity; if subjected to heat sealing, it will undergo shrinkage and deformation. Therefore, standard PET film does not possess heat-sealability.

Conventional PET is a crystalline polymer. After biaxial stretching and orientation, PET film exhibits a significant degree of crystallinity; if subjected to heat sealing, it will undergo shrinkage and deformation. Therefore, standard PET film does not possess heat-sealability.