Formation of hollow fibers in the melt-spinning process

This article reports an investigation of the formation of hollow fibers in a melt-spinning process. Experimental results indicate that die swelling is largely responsible for a negative effect on hole formation. The factors t hat positively affect die swelling, including a decrease in temperature, a decrease in capillary length, and an increase in shear rate, are thus not r ecommended for the spinning of hollow fibers. For vinyl-type polymers such as polypropylene, in which the apparent elasticity leads to serious die swe lling, the formation of hollow fibers is more complex than that of a typica l condensation polymer. Our results further demonstrate that when hollow fi bers are being made in a variety of shapes (but of the same denier), spinni ng a polygonal hollow fiber is significantly more unstable than spinning a circular one. Moreover, an asymmetric bridge along the polygonal contour le ads to a melt twist and interrupts the entire spinning process. (C) 2001 Jo hn Wiley & Sons, Inc.