Vitrimerization of crosslinked elastomers: a mechanochemical approach for recycling thermoset polymers

Abstract

Crosslinked poly (ethylene-vinyl acetate) (EVA) is extensively used in a wide range of applications including solar cell encapsulates and athletic shoes. However, recycling large amounts of crosslinked EVA (or EVA thermoset) waste is still a global challenge. Converting a permanent crosslinked network into a dynamic exchangeable network through a vitrimerization process is a cost effective and environmentally friendly method for recycling thermoset waste already present in the market. In this work, crosslinked EVA is vitrimerized with a catalyst via a mechanochemical approach. Zinc acetate is added as a catalyst and poly(vinyl alcohol) as a feedstock of hydroxyl groups to promote a dynamic exchange reaction that occurs via a transesterification mechanism. The vitrimerized EVA was reprocessed via extrusion and compression molding three times at low temperatures without additional catalyst or hydroxyl groups. This study shows that converting crosslinked EVAs into vitrimers using a mechanochemical approach is effective for three crosslinked EVA samples with different topology and vinyl acetate content enabling EVA waste to be recycled and reprocessed into value-added products.