Relationship between structure and spinning processing of as-spun PP fibres

As-spun polypropylene (PP) fibres, obtained under a onestep statistical exp erimental design using orthogonal arrays and involving all the common spinn ing parameters were studied with wide angle X-ray, scattering (WAXS). The W AXS results revealed that the micro-structure of PP fibres can be altered p rogressively from less-ordered paracrystalline states to highly-ordered cry stalline states with an alpha-monoclinic lattice. The degree of structural order has been evaluated quantitatively in terms of (W-1/2)(-1), the recipr ocal of the half-height width of the first WAXS reflection peak. On the bas is of such quantitative evaluation, which is shown to be consistent with th e conclusions derived from "traditional" qualitative assessment, comprehens ive quantitative analysis of the effects of processing parameters and their interactions on the degree of structural order is accomplished rising syst ematic but simple statistical methods. Parameters significantly affecting s tructure, including types of raw materials, winding speed, spinning tempera ture, application speed of spin finish and metering pump speed are identifi ed, and correlation between structure and parameter setting is established in a concise statistical model. The model indicates clearly the combination of parameter levels fbr increasing or reducing the degree of structural or der over the whole range from essentially amorphous to highly crystalline f orms. Comparisons with the "conventional" approach of "one factor at a time " demonstrated the validity of the new approach and its significant advanta ges. The latter incudes the economy in experiment scale, efficiency in resu lt analysis and a comprehensive overview of the process being studied, whic h covers effects arising from synergistic interactions as well as from indi vidual parameters.