Enhancement in the adhesion properties of polycarbonate surfaces through chemical functionalization with organosilicon coupling agents

Although polycarbonate (PC) materials are well known to have poor adhesion to other surfaces, few studies have been conducted on the improvement of their adhesive properties via surface chemical functionalization. Herein, we report the enhancement in the adhesion properties of PC by adapting two silane coupling agents, namely (3-glycidoxypropyl) methyldiethoxysilane (GPTMS) and (3-aminopropyl) trimethoxysilane (APTMS), on the surface. We tested the adhesion with an epoxy-based adhesive consisting of bisphenol A diglycidyl ether (BADGE) and trientine (trien). The chemical interaction between the amine groups of the hardener (trien) and the epoxy rings of an epoxy-functionalized PC (PC-GPTMS) sample surface was observed with X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. We found that the amine-functionalized PC (PC-APTMS) can also form crosslinked polymeric structures with the BADGE after curing. Compared to the bare PC, an increase in the shear strength of up to 168% and 163% was observed from the PC-GPTMS and PC-APTMS, respectively. In contrast, the ultraviolet-ozone (UVO) and O₂ plasma-treated samples showed a negligible increase in adhesion strength. These results strongly suggest that the chemical functionalization of PC substrates with coupling agents significantly enhances the adhesion properties of PCs.