Migration of Surfactants in Pressure-sensitive Adhesive Films and the Impact on Performance Properties

Results are reviewed from a study on the distribution of surfactants in pressure-sensitive adhesive (PSA) films subsequent to the coating process. The PSAs are water-based acrylics synthesized with n-butyl acrylate, vinyl acetate and methacrylic acid and two commercially available surfactants, disodium (nonylphenoxypolyethoxy)ethyl sulfosuccinate (anionic) and nonylphenoxypoly(ethyleneoxy) ethanol (nonionic). The ratio of these surfactants was varied, while the total surfactant mass content was held constant. Surfactant distributions in adhesive films were investigated using atomic force microscopy (AFM) and confocal Raman microscopy (CRM). AFM images demonstrate the tendency of the anionic surfactant to aggregates at film surfaces inhibiting latex particle coalescence, while CRM shows its enrichment near film interfacial regions. Results indicate that surfactant distributions are governed in large part by surfactant compatibility with the polymer phase. Also discussed is the influence of surfactant content and distribution on the performance of PSA films.