Impact response of recycled polypropylene-based composites under a wide range of temperature: Effect of filler content and recycling

This work aimed at investigating the thermal mechanical behavior of recycled polypropylene (PP)-based composites under dynamic loading. PP was blended by extrusion with different fractions of ethylene octene copolymer (EOC) as soft rubber toughening agent and talc as rigid reinforcing agent. To simulate mechanical recycling, the composites were grinded and re-extruded up to 6 times. The dynamic behavior was studied by means of a split Hopkinson pressure bar at various strain rates and temperatures. We found that neat PP and PP/talc composites presented a brittle behavior at low temperatures. The addition of EOC inclusions markedly improved the impact resistance of PP and PP/talc. The results also indicated that the impact resistance of PP/talc was improved with the recycling numbers due to a fragmentation of the talc particles during the reprocessing inducing a self-reinforcement. However, the impact resistance of PP/EOC decreased with the recycling due to chain scission mechanisms. Concerning PP/EOC/talc composite, its dynamic behavior was almost constant with the recycling number possibly induced by equilibrium between self-reinforcement and chain scission mechanisms. Complementary information about the dynamic behavior of the materials was deduced from optical microscopy investigation of the morphology after dynamic compression testing.