Functional self‐healable EVA elastomers based on reversible covalent networks: A potential new class of epoxy‐based specialty adhesives

Abstract

Multifunctional elastomers have gained tremendous attention in the material research community. In this study, an epoxy functionalized elastomer poly(ethylene‐co‐vinyl acetate‐co‐glycidyl methacrylate) (EVA‐GMA) that is commercially available was modified with dynamic covalent chemistry to make it self‐healable and recyclable, as well as to investigate its adhesive properties. EVA‐GMA was modified to a furfuryl‐appended diene elastomer (FA‐EVA‐GMA) and subsequently cross‐linked with bifunctional 1,2,4‐triazoline‐3,5‐dione (bis‐TAD) and bismaleimide (BMI) derivatives via electrophilic substitution (ES) and Diels‐Alder (DA) chemistry, respectively. The ES modification of the elastomer was ambiently completed using bis‐TAD, whereas its maleimide modification required elevated conditions (65 °C) with a longer time of 24 h. The tensile study showed a remarkable improvement in the mechanical strength upon cross‐linking the elastomers. The differential scanning calorimetry (DSC) analysis elucidated the thermoreversible characteristics of both the ES and DA‐derived networks, showing the cleavage of ES and DA conjugates at 135 °C (retro‐ES) and 140 °C (retro‐DA), respectively. The cross‐linked elastomers exhibited significant self‐healing characteristics (with a healing efficiency of ≈ 88%) and monitored using an optical microscope and tensile analysis. Interestingly, the bis‐TAD‐derived and bismaleimide functionalized EVA‐elastomer showed excellent adhesive properties toward the metal surfaces, as analyzed via lap shear test.