Ultraviolet Light-Sensitive Debonding Layer for Reducing Adhesion of Polymer Adhesives for Recycling

Separating adhesives from substrates is important for recycling metals and polymer materials used in a variety of applications such as food packaging and electronics. A proof-of-concept self-assembled debonding layer for debonding adhesives on demand is developed in this research. The debonding layer is applied to a silica surface in three steps. These steps were characterized with sum frequency generation (SFG) vibrational spectroscopy, X-ray photoelectron spectroscopy (XPS), and contact angle goniometry. SFG data shows characteristic signals from each step of the reactions to build the debonding layer. Once the debonding layer is fully prepared, the UV sensitivity was also tested. The results showed that a well-ordered debonding layer can be prepared on a silica surface and the UV-sensitive bond breaks when exposed to UV light. Before debonding the UV-sensitive group on the debonding layer, adhesives could be applied, resulting in an adhesive interface that can be selectively broken. Two adhesive materials, poly(dimethyl siloxane) (PDMS) with a silane adhesion promoter and an epoxy system of diglycidyl ether (BADGE) cross-linked with a diamine compound, were studied and applied to the debonding layer on a silica surface to determine the efficacy of the debonding mechanism. Along with spectroscopic studies, adhesion tests were performed on silica/adhesive and silica/debonding layer/adhesive samples before and after UV irradiation exposure, showing that the debonding by UV light could reduce the adhesion strength. This study lays the groundwork for development of an interfacial debonding layer that reduces adhesion of adhesive polymers from a silica surface as well as other substrates with UV light.