Recyclable and Reprocessable Epoxy Vitrimer Adhesives

Epoxy-based vitrimers represent a promising option toward sustainability and circular economy in automotive structural applications. In this work, a series of vitrimer materials are presented to be used as recyclable and reprocessable adhesives for such applications. These formulations consist of diglycidyl ether of bisphenol A-anhydride systems with glutaric anhydride and glycerol as cocuring agents in several proportions and 1,5,7-triazabicyclo[4.4.0]­dec-5-ene (TBD) or 1-methylimidazole (1MI) as catalysts. The materials obtained revealed relatively high T g s, up to 85 °C, as well as a homogeneous network structure. They also showed complete stress relaxation in times as short as just 3.6 min at 180 °C. The presence of TBD in the vitrimer allows the fastest relaxation. The thermosets were recycled and reprocessed through alcoholysis and mechanical grinding. These formulations were also applied as adhesives for mono- and multimaterial joints showing values of single-lap shear stress as high as those shown by commercial adhesives. Reversible adhesion was also studied after joint failure and after debonding without failure. In summary, the materials and methodology presented here represent a comprehensive study of recyclable and reprocessable epoxy-based vitrimers.