Upcycling of Ethylene-Vinyl Acetate Copolymer Through Hydrolysis and Reactive-Filling into Polyurethane Resins

Although ethylene-vinyl acetate (EVA) resin is recyclable, its properties degrade after a few processing cycles. Furthermore, when crosslinked, the resulting material loses its recyclability altogether and cannot be reprocessed even once. These End-Of-Life (EOL) and crosslinked EVA wastes are simply disposed of in landfills, where they persist for extended periods and contribute to environmental pollution. To address this challenge, we report an upcycling method that involves hydrolyzing EVA into ethylene-vinyl alcohol (EVOH) and incorporating it as a surface-reactive filler in polyurethane (PU) resins. The EVOH particles were uniformly dispersed within the PU matrix without any aggregation, demonstrating the strong reactive compatibility between the polyolefinic dispersed phase and PU resin. Compared to the unmodified PU resin, the EVOH-modified PU exhibited enhanced tensile and compressive strengths, due to urethane linkages formed between EVOH and PU, and improved strain at break, resulting from EVOH's plastic deformation. This approach offers a promising solution for managing EOL and crosslinked EVA waste, which face significant limitations in conventional recycling and pyrolysis, while simultaneously reducing the cost of PU resin.