The Effect of PP and Peroxide on the Properties and Morphology of HDPE and HDPE/PP Blends

Peroxide cross-linked high-density polyethylene (HDPE) and blends of HDPE and polypropylene (PP) were prepared by reactive extrusion. The effect of dicumyl peroxide (DCP) and PP on the properties and morphology of HDPE and blends was studied. The addition of DCP decreased the melt flow rate (MFR) and increased the HAAKE torque and impact strength in both systems. The elongation at break was increased at low DCP concentration (0-0.1 wt%) and then decreased at high DCP concentration. The addition of PP slightly decreased the MFR and mechanical properties of peroxide cross-linked HDPE. With the addition of DCP, the molecular weight was increased and the molecular weight distribution was broadened in both systems. Scanning electron micrographs of the fracture surfaces indicate that HDPE/PP blends are indeed a two-phase system. With the addition of DCP, the compatibility of the two phases was improved, resulting in an increase in the impact strength. (C) 2012 Wiley Periodicals, Inc.