Interfacial Separation of Insert Injection-Molded PS/Al Joints Induced by a UV/Heat-Activated Foaming Polymer

This paper presents the results of a study on the use of a thermoacid-triggered delamination system based on poly(tert-butoxycarbonyl styrene) [p(t-BocSt)] for controlling the separation of polystyrene/aluminum (PS/Al) insert injection-molded joints. The concept relies on a double-unlocking mechanism in which irradiation by ultraviolet (UV) light and subsequent thermal treatment are required to activate foaming within the p(t-BocSt) layer. Morphology study confirmed that uniform, defect-free interfaces were obtained prior to foaming, whereas postactivation samples exhibited pore formation and localized delamination due to CO2 and isobutene gas release during thermal decomposition. Tensile shear testing showed the PS/Al joint strength to be approximately 326 N for a single coating layer. Following the foaming process, the joint strength decreased by up to 84%, demonstrating that interfacial weakening and separation could be precisely controlled by the activation sequence. Overall, the proposed p(t-BocSt) system provides a controllable and separable polymer–metal bonding platform.