Methods for enhancing the bonding strength of thermoset adhesives and sealants via disulfide dynamic chemistry

A method of bonding a first substrate to a second substrate, wherein the method is carried out with an adhesive composition without the use of organic solvents, the method comprising:

• applying the adhesive composition in a wet state to a surface of the first substrate, the adhesive composition comprising epoxy-functional molecules having at least two epoxy groups and crosslinkers comprising at least two reactive amine groups and a disulfide bond;
• curing the applied adhesive composition at a first temperature that induces epoxy groups of the epoxy-functional molecules to react with amine groups of the crosslinkers to form a crosslinked polymer film;
• before, during, or after the curing of the applied adhesive composition, applying the second substrate over the adhesive composition, such that the adhesive composition is between the first substrate and the second substrate;
• and
• annealing the crosslinked polymer film at a second temperature that is higher than the first temperature and that induces the cleavage and reformation of the disulfide bonds, wherein the annealing of the crosslinked polymer film takes place while the crosslinked polymer film is between the first substrate and the second substrate and forms an adhesive bond between the first substrate and the second substrate.