PRODUCTION OF THERMALLY STABLE POLYPROPYLENE FIBERS

Polypropylene (PP) fibers were made with a number of different process ing conditions, such as one-stage drawing, two-stage drawing, and a co mbination of drawing, annealing, and relaxation. The thermal stability of these fibers in terms of shrinkage in length at 100, 130, and 150 degrees C was studied. It was found that the thermal shrinkage can be greatly improved with multi-stage drawing and with annealing. The fibe rs that were two-stage-drawn, relaxed, and then annealed remained stab le at 130 degrees C while still having a fiber tenacity in excess of 0 .8 N/tex. Thermal stability at 150 degrees C was more difficult to imp rove. However, the fibers that were drawn in three stages with a final drawing temperature of 185 degrees C showed thermal shrinkage at 150 degrees C of less than 10%. Finally, it was found that the thermal shr inkage of PP fibers at 150 degrees C can be greatly reduced by blendin g a minor component of a liquid crystal polymer into the PP fibers. Wi th two-stage drawing and annealing, fibers with shrinkage at 150 degre es C of only 2.9% were produced. (C) 1996 John Wiley & Sons, Inc.