The effects of molecular weight

molecular weight distribution and melt-spinning conditions of polypropylene resins on texture formation and non-uniformity of polypropylene fibers were investigated. The as-spun polypropylene fibers produced by melt spinning frequently exhibit diameter fluctuations. Pure rheological studies on this phenomenon were made by many authors

but our experiment showed that the orientation fluctuation and the crystal-linity difference of as-spun fibers make trouble much more severe than fiber diameter fluctuation does in the polypropylene spinning process. Since the mechanical properties of fibers

such as yield stress and initial modulus

depend on the orientation and crystallinity of as-spun fibers

the stretchability of as-spun fiber becomes worse with increasing orientation fluctuation and cry-stallinity. That means flow-induced crystallization plays a predominant role in fiber uniformity of polypropylene spinning process. Therefore

in order to improve the streching behavior of the as-spun fibers and the quality of the product fibers

the texture together with its uniformity of the as-spun fibers should be controlled by a reasonable choise of polypropylene resin as well as spinning condition.