Enhanced Mechanical Recycling of Polymer Mixtures by a Trifunctional Dynamic Crosslinker

Mechanical recycling of mixed post-consumer apolar/polar polymers, due to their mis-matched polarity and inherent immiscibility, is typically a downcycling process yielding brittle materials. An emerging method that can enhance recycling of such mixtures into dynamically crosslinked, high-performance thermosets is a dynamic crosslinker (DC) platform; however, current DCs typically require an external catalyst and, due to their insufficiently high peak activation temperature (T_a <190°C), are limited to a subset of applicable polymers and unsuitable for industrial melt-extrusion processing of high melting temperature (T_m) polymers. Herein, we report a trifunctional DC incorporating three sought-after properties: thermally robust pyridotriazole cores as the high-T_a (245°C) crosslinking sites compatible with reactive extrusion up to 270°C; dynamic siloxane linkages as the robust yet exchangeable bonds; and pyridine/ester functionalities as the internal catalysis sites devoid of external catalysts. Overall, this self-catalyzed, high-T_a DC can compatibilize waste plastic mixtures containing high T_m polymers and impart the recycled mixtures with superior thermoset properties such as enhanced creep resistance and thermomechanical stability while being melt-(re)processable.