Reversible adhesives from epoxy-based transesterification-induced vitrimers

Vitrimers are a class of materials that combine the excellent mechanical performance of thermosetting polymers with the malleability of thermoplastic polymers. One of the applications that most benefits from these features is structural adhesives. In this work, epoxy-based vitrimers from diglycidyl ether of bisphenol A, succinic anhydride, and trimethylolpropane are used as reversible adhesives. These materials show glass transition temperatures up to 80 °C as well as a homogeneous network structure. They also show high lap-shear stress values of up to 26 MPa. These adhesives are suitable for reversible adhesion thanks to their excellent vitrimeric behavior, with characteristic relaxation times that are under 10 min at 180 °C. This allows for the re-utilization of the same joint through re-adhesion after failure, the dismantling of adhesive joints with posterior re-bonding, and the application of the adhesive as a coating to make the joint in a different stage. The re-adhesion reaches values up to 96% with respect to the values of the first adhesion. Finally, chemical recycling is achieved through alcoholysis in ethyleneglycol, and this methodology is used to remove adhesive remains from adherend plates, so that they can be used for any other purpose. In summary, these vitrimer adhesives not only show high adhesion shear stress, suitable for structural applications, but also allow re-joining the bond in case of failure, the dismantling of the joint at the end of the bond lifetime, thermally activate the adhesive joint, and recover the adherends to be used for another purpose.