The drawability of as-spun polypropylene (PP) filaments was studied using a statistical approach including an experimental design and statistical analysis. The use of a statistical experimental design allows all possible interactions as well as main factors to be evaluated. As a result, one two-factor interaction (between winding speed and metering pump speed, WS*MPS) and two main factors (winding speed WS and metering pump speed MPS) were identified as factors having statistical significance on drawability of as-spun PP filaments with risk levels (P values) less than 0.005. The drawability can be improved by controlling the structure of the as-spun filaments, that is a paracrystalline structure combined with a very low overall orientation (birefringence ≤3.2 x 10^{– 3}). Application of twostage drawing also increases the drawability compared with one-stage drawing.

Direct link: http://www.polymer-process.com/IPP1863