Enhanced Mechanical Recycling of Polymer Mixtures by a Trifunctional Dynamic Crosslinker

ABSTRACT 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.