CHARACTERIZATION AND BEHAVIOR OF PARTIALLY ORIENTED POLY(ETHYLENE TEREPHTHALATE) FIBERS (POLYETHYLENE)

A low-temperature dyeing technique of poly(ethylene terephthalate) POY fibers revealed interactions of spin finish containing pure or close derivatives of poly(ethylene glycol)s with the POY fibers that bring about dye blocking. The thermal behavior of the POY fibers was characterized by shrinkage, shrinkage stress relaxation and DSC techniques.; Hypothetical modes of crystallization that bring about the observed shrinkage and shrinkage stress relaxation patterns are given. The effects of the spin finishes on the thermal behavior were correlated with the dyeing results.; The Critical Dissolution Times and amine etching resistance of the fibers showed again the same dependence on the nature of the spin finishes where in pure poly(ethylene glycol) the interactions are most effective in a narrow molecular range of 500 (+OR-) 100.; Characterization techniques including wide-angle x-ray diffraction, Raman and Infrared Attenuated Total Reflectance spectroscopy, birefringence, Rheovibron and Instron mechanical tests showed that the effects of the finishes are associated with increases in the degrees of intermolecular cohesion of the poly(ethylene terephthalate) molecules. Morphological studies including scanning electron microscopy, light and ultraviolet microscopy revealed a "skin-core" structure in the POY fibers.; The dyestuff was found to be confined to the skin which has high degrees of free volume and voids according to the results of the sorption isotherms of water and mercury porosimetry experiments.; Shrinkage tests revealed that the interaction of the carrier with the fiber that promotes the dyeability involves crystallization.; Kinetic studies of the low-temperature dyeing showed regular Fickian diffusion in the unblocked fibers, while the finish-blocked fibers showed two stages: a Fickian diffusion to an intermediate equilibrium dyestuff concentration, followed by a sigmoidal increase of the dye uptake.; It was found that the carrier diffusion is the rate-determining process and that the change from the typical Fickian to the sigmoidal shapes occurs above a minimum concentration of the carrier in the fibers.