Dyeing behaviour and light fastness of poly(ethylene terephtalate) films: a correlation with the morphological structure.

Isotropic poly(ethylene terephthalate) films, when thermally treated above 180°C, showed an inversion in dyeing behaviour as well as in light fastness. Similar results were found with anisotropic samples thermally treated above 150°C. The morphological characterization of the films showed the inversion points to occur always at a crystallinity index of about 0.5, but with larger crystallite dimensions in the anisotropic samples. The phenomenon is interpreted assuming that dye diffusion can be explained by replacing the usual "free volume" model by the "pore" model.