Extensional flow-induced crystallization in polyethylene melt spinning

Abstract

Polyethylene was spun into a heated chamber, with the spin-line temperature controlled in the range of 90-120°C. Within narrow limits, the stretch rate of the fiber was also controlled. Spin-line and crystallization onset conditions were characterized. Characteristics of fibers as-spun were measured via wide-angle x-ray scattering (WAXS), density, scanning electron microscopy, and differential scanning calorimetry. Spin-line data indicate that elongational flow enhances crystallization rate and that time under spin-line conditions is an important parameter. Analysis of WAXS data shows a typical "b-axis radial' orientation, the details of which change with spin-line parameters. This orientation is consistent with growth of lamellar crystals on extended-chain fibrils (shishkebab model). Other physical data are also consistent with this microstructure. Microcamera x-ray patterns show a similarity of microstructure generation in spinning and drawing.