Carrier effect on structure and properties of heat-treated poly(ethylene terephthalate) fibers .2. Dyeing behavior

The changes in the morphology of heat-setted poly (ethylene terephthalate) (PET) fibers (as spun and 2.8X) submitted to benzoic acid action at different concentrations and times were analyzed by wide-angle x ray scattering and dynamic and mechanical thermal analysis. Also, dyeings in the presence of two different Disperse dyes were performed. Therefore, the calculated diffusivities as well as the dye absorption percentage at equilibrium were related to the morphological changes of the fibers, due to the benzoic acid action. The plasticization effect of the benzoic acid over the as-spun fiber occurs in the first 30 min of exposition and in 24 h for the drawn one. This plasticizing action of the benzoic acid seems to be the commanding factor over the dyeing behavior of the fibers, as demonstrated by an increase of the diffusion coefficient with the increase of benzoic acid concentration. However, the morphological changes due to exposition for long periods of time at increased benzoic acid concentrations are one of the major responsible factors by the observed maxima in the figures of percentage of dye on the fibers at equilibrium versus benzoic acid concentration. Also, changes in the angular coefficient (B) calculated from the free volume theory equation are indicative that factors such as the size of the dye molecules as well as their solubilities in water in addition to the morphological changes may be playing a role in the dyeing behavior. (C) 1996 John Wiley & Sons, Inc.