Photothermal synergistic curing of one-component epoxy resin adhesive based on active monomer mechanism

One-component epoxy resin adhesives with Ethylamine-boron trifluoride (BF3-MEA) have become popular choices for electronic applications due to their lower curing temperatures and excellent storage stability. However, in the traditional thermal curing process for these adhesives, which relies on the Active Chain End (ACE) mechanism, the formation of cyclic oligomers can compromise their mechanical performance. In this study, we prepared a series of novel one-component adhesives using Diglycidyl-4,5-epoxy-cyclohexane-1,2-dicarboxylate (TDE-85) epoxy resin, Bis [4-(diphenylsulfonio) phenyl] sulfide bis (hexafluoroantimonate) (Photoinitiator 1176), and BF3-MEA through blending, and successfully achieved photothermal dual-curing. We systematically explored various adhesive ratios and curing conditions. Compared to adhesives treated solely by thermal curing, those subjected to photothermal dual-curing exhibited the best shear strength of 13.9 ± 0.7 MPa and a hardness of 88 ± 4 Shore A, representing improvements of 118.2% and 18.9%, respectively. Additionally, the study demonstrated that hydroxyl groups produced by photocuring effectively inhibit the ACE mechanism and promote the Active Monomer (AM) mechanism, which becomes dominant. In summary, the photothermal synergistic curing approach, with the AM mechanism as dominant, prevents the formation of cyclic oligomers and enhances mechanical performance. This study offers a new approach for adhesives used in electronic devices.