Self-reinforcement of high-density polyethylene low density polyethylene prepared by oscillating packing injection molding under low pressure

This article reports the toughness improvement of high-density polyethylene (HDPE) by low-density polyethylene (LDPE) in oscillating packing injection molding, whereas tensile strength and modulus are greatly enhanced by osci llating packing at the same time. Compared with self-reinforced pure HDPE, the tensile strength of HDPE/LDPE (80/20 wt %) keeps at the same level, and toughness increases. Multilayer structure on the fracture surface of self- reinforced HDPE/LDPE specimens can be observed by scanning electron microsc ope. The central layer of the fracture surface breaks in a ductile manner, whereas the break of shear layer is somewhat brittle. The strength and modu lus increase is due to the high orientation of macromolecules along the flo w direction, refined crystallization, and shish-kebab crystals. Differentia l scanning calorimetry and wide-angle X-ray diffraction find cocrystallizat ion occurs between HDPE and LDPE. (C) 1999 John Wiley & Sons, Inc.