KH ‐560 Silane Modification for Enhancing Adhesion of UV ‐Curable Acrylic Pressure‐Sensitive Adhesives on Low‐Surface‐Energy Substrates

ABSTRACT UV‐curable acrylic pressure‐sensitive adhesives (PSAs) have attracted considerable attention for their high curing efficiency and strong adhesion to diverse substrates. However, their broader application is hindered by poor adhesion to low‐surface‐energy substrates, elevated‐temperature creep, and an intrinsic trade‐off between cohesive strength and adhesion. To address these limitations and improve adhesion to low‐surface‐energy substrates, the dual reactivity of the silane coupling agent KH‐560 was investigated in UV‐curable acrylic PSAs. Covalent grafting was achieved through epoxy–carboxyl coupling agent via ring‐opening esterification, while a Si–O–Si crosslinked network was formed through in situ hydrolysis and condensation of alkoxysilane moieties, enabling optimization of surface and bulk properties. When appropriate amounts of KH‐560 were incorporated into PSAs coated on an as‐received (untreated) polyethylene terephthalate (PET) substrate (surface free energy≈45–49 mN m −1 , as estimated by the OWRK method), the 180° peel strength of the modified PSAs increased by about 150%, the shear holding time increased by more than 100%, and the initial tack was improved, while the retention after aging and water immersion remained above 90%. Incorporation of KH‐560 reduced the surface energy of the PSAs from 35.2 to 27.7 mN m −1 , thereby significantly enhancing wetting on low‐surface‐energy substrates. From microstructural characterization, these improvements were attributed to optimized wettability due to siloxane migration, combined with energy dissipation of the Si–O–Si network caused by restricted chain mobility.