HIGH SPEED MELT SPINNING OF POLY (ETHYLENETEREPHTHALATE)

Abstract

PET filaments have been produced by the high speed melt spinning method in the range of take-up velocity 1, 000 to 9, 000m/min. With the increase in the velocity, a fiber structure developes to highly orientation state. Above 7, 000m/min, the density and birefringence of the fibers begin to decrease, whereas the degree of crystallinity measured by heat of fusion shows levelling-off.In addition, SAXS pattern changes from “X” shaped four spot reflection to two spot meridial reflection. Crystalline region has almost fully oriented structure, whereas the degree of amorphous orientation is relatively low and shows a maximum at 6, 000m/min. From the results of SAXS and WAXS patterns for the fibers before and after an alkali treatment and of dye penetration coefficients of as-spun fibers, it is pointed out that the fibers spun at extremely high take-up speed involve a large amount of void in the skin layer. The degree of molecular orientation and crystallinity are higher at the skin than at the core and the difference in the birefringence between skin and core (radial variation in fiber) increase with increasing take-up velocity. Development of the radial variation is attributed to temperature and stress distribution in the fiber cross section which are caused by the rapid quenching from the skin layer and by the increase in the crystallization rate induced by the molecular orientation.