Thermo-mechanical recycling via ultrahigh-speed extrusion of film-grade recycled LDPE and injection molding

The analysis of the mechanical recycling market in North America indicates that flexible packaging is the most significant end-use application of PE (i.e., > 40%), with a domestic recycling rate lower than 10%. Several technical barriers currently hinder film and flexible plastics recycling, including feedstock contamination, lack of stability and coordination in the supply chain, inefficient sorting, poor processing capabilities, and lack of end markets. In this work, we use ultrahigh-speed extrusion to modify the molecular weight of film-grade LDPE to promote its recycling via injection molding. The extrusion process is analyzed considering the effect of screw speed and feed rate on the rheology of the modified materials. The modified LDPE was injection molded using a novel pressure-controlled injection molding strategy. The tensile testing of the parts manufactured using the modified material showed a slightly reduced elastic response and significantly lower elongation at break. The sustainability analysis for the proposed combination of ultrahigh-speed extrusion and injection molding showed that the embodied energy is substantially lower than that obtained from the injection molding of the virgin LDPE. The energy saving can be converted to CO2 emissions showing that the proposed process could save 6 kg of CO2 for each kg of LDPE converted into an injection molded product.