Structure of uniaxially drawn poly(ethylene terephthalate) films and its influence on dye sorption

Abstract

Drawing temperature, draw ratio, and tension during thermal treatments were varied to obtain poly(ethylene terephthalate) (PET) films with different structural modifications. These PET films were disperse dyed using a C.I. Disperse Blue 7 dye. Qualitative and quantitative characterization of molecular order and orientation was carried out using infrared spectroscopy and x-ray diffraction methods. Dye sorption was inferred from reflectance measurements using an optical spectrophotometer. It was observed that there was no unique dependence of dye uptake of poly(ethylene terephthalate) films on either orientation or crystallinity separately. Structural models have been proposed to explain the dye sorption behavior with special emphasis on the efficiency of chain packing, tortuosity, or compactness of the structure as an important criterion in governing the diffusion of dye molecules into the film matrix.