Effect of Few-Layer Graphene on the Properties of Mixed Polyolefin Waste Stream

Abstract

This work demonstrates how the addition of few-layer graphene (FLG) influences the processability and mechanical properties of the mixed polyolefin waste stream (R-(PE/PP)). Three different types of compounds were investigated: (1) R-(PE/PP) with FLG; (2) blends of R-(PE/PP) with prime polyethylene (PE) or polypropylene (PP) or PP copolymer; and (3) R-(PE/PP) with both the prime polymer and FLG. The processability was assessed by measuring the torque during melt extrusion, the melt flow index (MFI), and viscosity of the compounds. Investigations of the processability and mechanical properties of the composites indicate that the presence of FLG can reinforce the composites without hindering the processability, an unusual but desired feature of rigid fillers. A maximum increase in tensile strength by 9%, flexural strength by 23%, but a reduction in impact strength were observed for the compounds containing R-(PE/PP), 4 wt.% FLG, and 9 wt.% prime PP. The addition of FLG concentrations higher than 4 wt.% in R-(PE/PP), however, resulted in higher tensile and flexural properties while preserving the impact strength. Remarkably, the addition of 10 wt.% FLG increased the impact strength of the composite by 9%. This increase in impact strength is attributed to the dominant resistance of the rigid FLG particles to crack propagation.