Characteristics of Crystallization of Fibers in the Formation of Filaments from a Mixture of Polypropylene with Small Amounts of Polyethylene

Resumo

X-ray diffraction analysis shows that in complex polypropylene filaments (CPF) modified with lowdensity polyethylene (LDPE) the latter is present as a single anisotropic phase. It has been proven that LDPE promotes further crystallization of polypropylene (PP) in the production of CPF due, apparently, to the mutual influence of the PP chains and LDPE within the amorphous phase providing increased segmental mobility of the molecules and the additional formation of small crystallites of PP, in particular, in the transition from lamellar sheet structure to fibrillar formations of stretched chains during orientational drawing. The PP crystallization effect manifests to the maximum extent at low concentrations of LDPE in CPF – 0.5-7.5 wt. %. Introduction of high density polyethylene (HDPE) into CPF to a lesser extent promotes crystallization of PP in comparison with LDPE, which can be due to structural features of the crystalline phases of polyethylene present in the fibers determining their different effect on the mobility of macromolecules in the matrix of fibers and, consequently, the crystallization of polypropylene during thermal drawing of the fibers.