Morphological changes of poly(ethylene terephthalate) (PET) film during degradation in an aqueous ethylamine solution at room temperature were examined using photomicrographies. Sample films used in this study were prepared by stretching and annealing the melt quenched amorphous PET film, as shown schematically in Fig. 1.The more crystalline and highly oriented the specimen is, the lower is the rate of the weight loss during the aminolysis (Fig. 2-4). This indicate that ethylamine selectively etches the amorphous PET chains.In the case of non-crystalline film (Fig. 5), the etching pattern was sensitive to the chain orientation anisotropy. For the crystalline films (Fig. 6-8), the etching pattern mainly occurs perpendicularly to the draw direction in accordance with the formation of folded-chain crystals during annealing.The changes of weight loss and of the melting behavior are in accordance with the results from the microscopy.

A study was made of the morphological changes of crystalline fine texture that occurred when poly(ethylene terephthalate) films were degraded in aqueous ethylamine at room temperature. Earlier works proposed that photomicrographies applied to the investigation of the etching patterns were sensitive technique to detect the differences of orientation anisotropy and amounts of crystallinity for PET films which had different mechanical and thermal history. In the present work X-ray measurements were used to deduce the information on the occurring of the various etching patterns based on the structural changes of the crystallite orientation, the size of crystallite, the long period spacing and the distributions of the size of laminar domains by the degradation of films.