Improving the low-temperature toughness of PPR pipe by compounding with PERT

In this research, multi-layer co-extrusion technology was adopted to prepare Polypropylene random copolymer (PPR)/Polyethylene of raised temperature resistance (PERT) composite pipes. The structures and mechanical properties of PPR/PERT composite pipe were investigated by scanning electron microscopy (SEM), Dynamic thermomechanical analysis (DMA) and impact test systematically. It was found that PPR and PERT obey different deformation mechanism at low temperature. When tested at -50 °C which is lower than the glass transition temperature (Tg) of PPR, the molecular chains of PPR are frozen, which leads to the high notch sensitivity and extremely low impact strength of PPR/PERT pipe. Nevertheless, PERT whose Tg is about -78 °C could effectively inhibit the initiation and propagation of crack and therefore improve the low-temperature toughness of PPR/PERT composite pipe significantly. Furthermore, we found that the composite pipe of PPR/PERT-2:1 could combine the stiffness of PPR and the toughness of PERT most effectively, resulting in the optimized performances of PPR/PERT pipe.