Enhancing adhesion strength via synergic effect of atmospheric pressure plasma and silane coupling agent

To facilitate the widespread use of carbon fiber reinforced thermoplastic polymer (CFRTP), enhancing its adhesion strength with other materials is crucial. In this study, we investigated the synergic effect and underlying mechanism of atmospheric pressure plasma and silane coupling agent on the adhesion improvement of CFRTP. The plasma/mercapto-silane-treated CFRTP demonstrated a remarkable 282% increase in adhesion strength compared to untreated CFRTP. Our post-fracture analysis revealed that the weakest CFRTP/adhesive interface was fortified, resulting in a shift in the failure mode from adhesive to substrate. Equipment analyses indicated that plasma and silane coupling agent contributed to the formation of C-O and Si-O-Si linkages, respectively. The application of both treatments led to the creation of a macro-network at the CFRTP/adhesive interface through both linkages, which resulted in a much more substantial increase in adhesion strength than either treatment alone. Lastly, we propose guidelines for enhancing the adhesion strength of CFRTP by elucidating the dependence of the synergic or antagonistic effect on the organofunctional group in silane coupling agent.