Aging-dependent interfacial energetics and adhesion stabilization of reactive silicone-modified acrylic pressure-sensitive adhesives

Reactive silicone additives can reduce interfacial adhesion in acrylic pressure-sensitive adhesives (PSAs), but excessive silicone mobility or loading may cause adhesion variability, cohesion loss, and surface residue. This study investigates the aging-dependent interfacial energetic evolution and peel-adhesion response of a low-dose reactive silicone-modified acrylic PSA laminated onto copper under high-temperature and high-pressure conditions. The central premise is that the functional interfacial state is not fully established immediately after manufacture but evolves during post-aging. Room-temperature aging progressively decreased the calculated surface energy from 32.7 to 26.2 mN/m and reduced low-speed peel adhesion from 247 to 219 gf/25 mm, indicating an aging-dependent shift toward a lower-adhesion interfacial state. Because PSA peel adhesion is governed by both the interfacial work of adhesion and bulk viscoelastic dissipation, the peel response is interpreted as a coupled interfacial–viscoelastic response rather than as a direct measure of interfacial energy alone. Subsequent thermal aging at 50 °C reduced adhesion variability and promoted convergence toward a narrower peel-response window, with the mean adhesion decreasing from 247 to 211 gf/25 mm over seven days. X-ray photoelectron spectroscopy confirmed the presence of silicone-related species within the near-surface region, but did not indicate measurable progressive silicone enrichment during aging. Therefore, the observed aging-dependent adhesion evolution is interpreted as reaction-coupled interfacial energetic evolution of an already silicone-containing near-surface region, accompanied by apparent stabilization of the peel-adhesion response. This study clarifies the importance of post-aging in defining the final adhesion response of low-dose reactive silicone-modified acrylic PSAs.