Nucleator-Enhanced Molecular Orientation and Crystallization in Melt-Spun Monofilaments of Syndiotactic Polypropylene.

Different from other semi-crystalline polymers, the crystallization of syndiotactic polypropylene (sPP) into helical sequences under flow is largely inhibited due to favorable formation of trans-planar conformations. The results presented in this study, using micro-FTIR, 2D-WAXS, and 2D-SAXS characterization, indicate that molecular orientation and crystallization in melt-spun sPP monofilaments can be dramatically enhanced by a sorbitol-based nucleator. It is suggested that, similar to the oriented crystallization in the nucleated isotactic polypropylene (iPP), the phase-separated nanofibrils, aligned under flow prior to sPP crystallization, act as shish structure (primary nuclei) to mediate the molecular orientation and crystallization of sPP. [ABSTRACT FROM PUBLISHER]