RELATIONSHIPS BETWEEN THE PROPERTIES OF FIBERS AND THERMALLY BONDED NONWOVEN FABRICS MADE OF POLYPROPYLENE

Typical polypropylene fibers for use in light nonwoven fabrics were pr oduced in a full-scale compact-spinning line. Molecular weight distrib ution (MWD), extrusion temperature, draw-down ratio, and draw ratio we re varied. The fibers were thermally bonded (welded) into nonwoven fab rics, at different bonding temperatures, using a pilot calender line. The tensile properties of the fabrics are influenced by the MWD and th e processing conditions of the fibers, and the effects of these fiber parameters increase with increasing bonding temperature. The fabric st rength increases with increasing M(w)/M(n), decreasing draw ratio, and increasing extrusion temperature, while in all these cases the fiber strength generally follows the opposite trend. Furthermore, the fabric strength, as well as the fiber strength, have a maximum as a function of draw-down ratio. The tensile properties of the fabrics seem to be governed by the bonding properties of the constituent fibers, not the fiber strength per se. Bond characteristics are discussed in terms of skin-core structures. Some details of the macroscopic fracture mechani sms of fabrics were revealed by scanning electron microscopy and the s hape of load-elongation curves. (C) 1995 John Wiley & Sons, Inc.