Adhesion properties of thiol-acrylate–epoxy polymer networks based on thiol–epoxy ‘click’ chemistry

This study examined the preparation of epoxy resins with enhanced mechanical strength, modified with thiol-acrylate segments integrated into the polymer network via a thiol–epoxy “click” reaction. Thiol-acrylate–epoxy polymers were synthesized using both single and dual curing processes. In the single curing process, a polythioether (thiol-acrylate) prepolymer was synthesized. The results showed that an epoxy formulation containing 30 wt% of this prepolymer achieved the highest lap shear strength, approximately 57% higher than that of neat epoxy. This improvement indicates strong interactions between the thiol-acrylate segments and the epoxy matrix due to the thiol–epoxy “click” reaction. Dual-cure systems exhibited slightly higher tensile strengths compared to single-cure systems, particularly as the thiol-acrylate segment content increased up to 20%, while also maintaining superior lap shear strengths. Incorporating thiol-acrylate segments raised the tensile strength to 34 MPa, about 25% higher than that of pure epoxy. Polymer networks containing 20–30 wt% of thiol-acrylate segments, in both single and dual-cure systems, demonstrated significant potential as effective adhesive systems. These findings contribute to the development of adhesives with enhanced tensile and lap shear strength, as well as the identification of suitable curing methods.