Polypropylene fibers melt‐spun in the presence of torsional shear

Abstract

Melt‐spun fibers of isotactic polypropylene have been formed using specific combinations of shearing and elongational flow. Such rheological conditions were achieved with a take‐up device capable of subjecting molten polymer filaments continuously to various combinations of torsional and elongational strains. Relationships were determined between mechanical properties of the resulting fibers and their molecular organizations. The results obtained indicated that these flow fields would produce fibers whose mean‐preferred‐chain‐orientation directions ranged between being tilted radially from a direction parallel with the fiber axis (no torsional shear strain imposed) and having some additional tilt that is tangential with respect to the fiber circumference (some torsional shear strain imposed). It is not possible to resolve the observed helical chain tilts into contributions from crystalline and amorphous regions, respectively.