Spinning, mechanical and thermal properties of metallocene polypropylene fibers

The higher mechanical properties of polypropylene (PP) fibers based on metallocene-catalyzed PP (miPP) in comparison with fibers based on Ziegler–Natta-catalyzed PP (zniPP) were presented in periodic literature in the last decade. At the same time the miPP fibers have lower crystallinity and lower melting temperature compared with conventional zniPP fibers. In our experimental work, the thermal and mechanical properties of both the miPP and zniPP multifilaments depending on their spinning and drawing conditions were investigated. The dynamic viscosity and deviation from the Newtonian flow of polymer melt were evaluated as important parameters for melt-spinning technology. The melting temperature, melting enthalpy and melting entropy of multifilaments were investigated using DSC analysis in dependence on spinning temperature and draw ratio of fibers. At the same time the mechanical properties of fibers tenacity, elongation and elastic modulus were measured. The DSC measurements were carried out using conventional method and constant length method at which the constant length of fibers was held (constrained fibers). The changes in melting temperature, melting enthalpy and melting entropy of drawn fibers were analyzed and correlated with mechanical properties of fibers. The mechanical and thermal properties of fibers were discussed with regard to the spinning and drawing conditions as well.