Abstract
The effect of dye and water on the molecular motions of poly (ethylene terephthalate) (PET) was investigated by dynamic viscoelastic measurements and thermal analysis of dyed PET films. Both α and β loss modulus peaks of dry films shifted to lower temperature side with the increase of dye concentration, accompanied by a decrease of their apparent activation energy. The results suggested that dye molecules in the films enhanced the segmental mobility of PET as a result of plasticizing effect. The number of segments per unit cross section derived from the relaxation intensity of β dispersion, which was associated with local mode relaxation of PET. depended on dye concentration in the films. It is expected that higher dye concentration brings about a different mode of dye adsorption in PET substrates. The apparent activation energy of α dispersion due to glass transition of PET decreased markedly in the presence of water. The segmental mobility of PET chains seem to be much sensitive to moisture content in the film as compared with plasticizing effects by dye molecules.
