THERMAL SHRINKAGE BEHAVIOR OF THE HEATED POLYETHYLENE TEREPHTHALATE FIBERS

Abstract

In order to discuss the thermal stability of the heat-treated P. E. T. fibers under varying heated conditions, temperature dependence of the longitudial changes and the relative optical retardation on sucessive and constant heating process were measured under tensionless state. The results obtained are shown as follows:1) Temperature dependence of the longitudial changes for non-heated P. E. T. fibers on successive and constant heating process is that shrinkage becomes larger with increased draw ratio. While the form of distribution on ΔS/ΔT_??_T curve becomes sharp for lower stretched filament, its form may skew and broaden towards higher temperature for higher stretched one. The temperature of peaks on ΔS/ΔT_??_T curves may correspond to the transformation temperature in a range of higher temperature on (relative retardation)_??_(temperature) curves. And the apparent activation energies in a range of lower temperature on shrinkage process become larger compared with range of higher temperature.2) Temperature dependence of the longitudial changes for heated P. E. T. filaments on successive and constant heating process is that shrinkage becomes smaller with increased heated temperature. Temperature behavior of the relative optical retardation for dry heated fibers may change extremly dependenent on heated temperature. The form of shrinkage distribution curves broadens and temperature of peaks shifts towards higher with rising heated temperarure, and height of peaks becomes lower. While the apparent activation energies of the filaments heated by drying and steaming on shrinkage process become lower with increasing heated temperature in a range of lower temperature, reversely, they may be larger in a range of higher temperature. And, their activation energies of filaments heated with hot water may be reversed for the above results.3) The height of peak on ΔS/ΔT_??_T curves and the apparent beginning temperature by shrinking estimated from (shrinkage)_??_(temperature) curves may be highly correlative with degree of crystallinity by X-ray method and contribution of the crystalline birefringence. Besides above results, it may be seen that they depend on the effects of broadenning of shrinkage temperature distribution, that is, moleculare aggregation state.