Impact behaviour of polypropylene/polyethylene blends

Abstract

Due to the large volume consumption of polyolefins, the treatment of the resulting solid waste is becoming a major concern. One possible utilization of the polyolefin wastes is to form blends from recycled polypropylene (PP) and polyethylene (PE). This study is a preliminary investigation on the impact fracture behaviour for the PP/PE blends. The impact testing method employed in this study includes the conventional and instrumented Izod impact tests, the instrumented Charpy impact test, and the instrumented drop weight plate impact test (IDWPIT). In both conventional and instrumented Izod impact testing, PP homopolymer and PP/LDPE blend have similar impact strengths, while PP/HDPE blend exhibits slightly lower impact strength. However, the instrumented Charpy impact test indicates that both PP/LDPE and PP/HDPE have similar impact strengths, and both are slightly lower than PP homopolymer. This suggests that the type of impact test employed is playing an important role in the impact fracture behaviour of the PP/PE blends. The effect of temperature on the impact fracture behaviour for the PP/PE blends was evaluated by means of the Charpy and drop weight plate impact tests. During the tests, impact strengths reduced with decreasing testing temperature. In the Charpy impact test, the impact strength for PP homopolymer was higher than those of the two PP/PE blends at both 20 and 0 °C. The Etotal measured from the IDWPIT indicated PP/LDPE has the highest impact strength at both 20 and 0 °C.