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.