Two-stage drawing of ultra-high molecular weight polyethylene reactor powder

Abstract

A two-stage drawing technique has been successfully applied for drawing of ultra-high molecular weight polyethylene reactor powder. Compacted powder films prepared below the ambient melting point of the initial powder was solid-state coextruded to a low extrusion draw ratio of 6 followed by tensile drawing at elevated temperatures of 120–135°C. The drawability for the second-stage tensile drawing and the uniformity of the resultant ultradrawn films were significantly affected by the drawing temperature and rate. The initial powder and drawn films were characterized by the tensile measurements, differential scanning calorimetry (d.s.c.) and X-ray diffraction. The results show the characteristic morphology of the reactor powder. Thus, the compacted powder films were effectively drawn up to a draw ratio of 77. Such highly drawn films exhibited tensile moduli up to 107 GPa. As the samples fractured by a repetitive partial rupture at the edge of cramp, the observed tensile strength at break were fairly low and in the range 1.0–1.4 GPa at a draw ratio range of 35 to 77.