Debonding of Pressure-Sensitive Adhesives: A Combined Tack and Ultra-Small Angle X-Ray Scattering Study

Summary: The debonding of pressure-sensitive adhesives (PSAs) is investigated by a combination of the mechanical tack test and ultra-small angle X-ray scattering (USAX). Two chemically different PSAs are investigated, namely the homopolymer poly(n-butyl acrylate) (PnBA) and a statistical copolymer with a monomer ratio of 80% 2-ethylhexyl acrylate (EHA) to 20% methyl methacrylate (MMA). Scattering yields additional structural information on a nanoscopic level, which is identified as nano-bubbles located inside the PSA film. Due to their size, these nano-bubbles are invisible with optical techniques. The probed nano-bubbles, as a substructure of vertically expanded adhesive material, show that the structure creation during debonding, which is well known at macroscopic length scales, also proceeds in the nanometer range.