(346c) Reclaiming Low-Value Plastic Waste and Natural Fiber for Composite Materials

The ever-increasing volume of municipal solid waste (MSW) is made up of a significant portion of plastic and natural fiber waste from labelled packaging, multilayer films, and comingled paper and plastic products. Most of the plastic waste is never recovered, attributed to the low value of most recycled products especially when mixed materials cannot be separated. The aim of this study was to recover poly(ethylene terephthalate) (PET) and natural fibers from MSW, targeting otherwise unrecycled mixed flexible plastics. Two recycling approaches were demonstrated: advanced compounding and manufacturing is a mechanical approach to transform these recyclates into fiber-reinforced polymer composites with superior properties. Enzymatic depolymerization is a chemical approach to recover monomers from the mixed PET-fiber waste streams when mechanical recycling is not viable. The compounding of these plastics with natural fibers was performed using twin-screw extrusion with devolatilization. Properties of the composites were evaluated using rheology, thermal testing, and mechanical testing, and related to the size of fibers incorporated and the extrusion processing variables. The enzymatic depolymerization approach was shown to be efficient and rapid with the appropriate enzyme selection. Advancing both approaches could lead to diverse end of life solutions depending on the original waste quality. Eventually, these efforts will result in significant reductions in consumption of primary feed stock, carbon dioxide emissions and energy.