MORPHOLOGY AND PROPERTIES OF SELF-REINFORCED HIGH-DENSITY POLYETHYLENE IN OSCILLATING STRESS-FIELD

This article reports the effect of mould temperature on the mechanical performance and microstructure of self-reinforced high density polyet hylene (HDPE) prepared by melt deformation in oscillating stress field . The mechanical properties of HDPE have been improved greatly in osci llating stress field. The Young's modulus and yield strength of HDPE h ave been enhanced from its original 1 GPa, 23 MPa into 3.5 GPa, 87 MPa , respectively. Differential scanning calorimetry (d.s.c.) curves of s lices taken from self-reinforced HDPE exhibit double-peak melting endo therm depending on their distances from the surface of the sample. The low-temperature peak is attributed to the presence of spherulites, an d the high temperature peak to the melting of shish-kebab crystals. Th e amount of shish-kebab crystals amounts to 20% in the crystalline pha se. Wide angle X-ray diffraction (WAXD) measurements show there exists preferred orientation of molecular chains. It is the production of sh ish-kebab crystals and the orientation of molecular chains that are or igins of the great improvement of mechanical behaviour of HDPE prepare d in oscillating stress field. (C) 1997 Elsevier Science Ltd.