Properties of syndiotactic polypropylene fibers produced from melt spinning

Molecular arrangement of syndiotactic polypropylene (sPP) is quite distinct from that of isotactic polypropylene (iPP), mainly due to its alternate positioning of methyl groups along the molecular chain. Also, during crystal packing, sPP assumes three main polymorphic forms based on the chirality, and positioning of its single chain helix. Depending on the thermal and mechanical history, packing defects and vacancies have been observed in sPP crystals (1). As a result, sPP fibers prepared from melt spinning, exhibit a low solidification rate, elastomeric properties even at room temperature and high shrinkage at elevated temperatures. An analysis of mechanical properties of sPP and iPP fibers is presented, on the basis of their x-ray diffraction patterns and dynamic mechanical behavior. Accordingly, sPP fibers have a low elongation and tenacity compared to iPP fibers, but a higher work recovery and lower permanent deformation, characteristics that are advantageous for making carpet fibers.