Rheological and mechanical properties of composites made from wood flour and recycled LDPE/HDPE blend

The effect of compounding method is studied with respect to the rheological behavior and mechanical properties of composites made of wood flour and a blend of two main components of plastics waste in municipal solid waste, low-density polyethylene (LDPE) and high-density polyethylene (HDPE). The effects of recycling process on the rheological behavior of LDPE and HDPE blends were investigated. Initially, samples of virgin LDPE and HDPE were thermo-mechanically degraded twice under controlled conditions in an extruder. The recycled materials and wood flour were then compounded by two different mixing methods: simultaneous mixing of all components and pre-mixing, including the blending of polymers in molten state, grinding and subsequent compounding with wood flour. The rheological and mechanical properties of the LDPE/HDPE blend and resultant composites were determined. The results showed that recycling increased the complex viscosity of the LDPE/HDPE blend and it exhibited miscible behavior in a molten state. Rheological testing indicated that the complex viscosity and storage modulus of the composites made by pre-mixing method were higher than that made by the simultaneous method. The results also showed that melt pre-mixing of the polymeric matrix (recycled LDPE and HDPE) improved the mechanical properties of the wood–plastic composites.