A transposable adhesive from an acrylic pressure-sensitive adhesive to semi-structural adhesive with self-healing function

This work presents a transposable adhesive in the form of reactive pressure sensitive adhesive (PSA) prepared from mixing acrylic copolymer and reactive components consisting of epoxy groups and acids, which exhibited different adhesion properties at different stages from a PSA to a semi-structural adhesive after activated by heat. In the first stage the adhesive showed well-balanced performances in terms of tack, peel and shear and the PSA behaved as a removable label with neat bond line. After activation the bonding strength was quickly increased due to the reaction between epoxide groups and carboxyl groups. Two acid-providers including glutaric acid and Carbomer and their effects on the PSAs and semi-structural adhesives were investigated. It is found that Carbomer, crosslinked poly (acrylate acid), played a significant role in static shear strength (>720 h), T g (85 °C), temperature resistance (132 °C) and modulus. Beside the transformation from PSA to a semi-structural bond, the transposition concept further includes restoring bonding after cohesion failure, due to the self-healing property under trans-esterification mechanism through hydroxyl groups. The results showed that the bonding had been restored up to 95.74% of the original strength. How likely the self-healing behavior took place and how the composition of adhesives influenced the healing efficiency, is also discussed in detail. • Carbomer as a cross-linked polymer, enhanced mechanical performance no matter before or after heat activation. • Due to embedded epoxide and carboxyl groups, PSA was transformed into a semi-structural adhesive with higher modulus. • The semi-structural adhesive exhibited self-healing capability up to 95.74%.