(10c) Interaction of Pressure Sensitive Adhesive Thin Films with Moisture

Acrylic water-based pressure sensitive adhesive (PSA) is produced via emulsion polymerization and formulated to allow for its processing and to impart certain performance properties. When dried to form thin films, these adhesives retain much of the amphiphilic chemicals used in their generation. The hydrophilic functional groups in the surfactants and adhesive polymers allow the films to readily sorb water and swell modifying their properties, performance and appearance. In this presentation, research on the interaction of model PSA films with moisture will be reviewed. The model formulations contain a broad range of monomer combinations and surfactant systems. Sorption and desorption of water to PSA films under a variety humidity and temperature conditions was examined using quartz crystal microbalance (QCM) gravimetry and the water vapor transmission of the films was analyzed. In addition, in-situ tensile, nanoindentation and performance testing were carried out on moisture exposed films. The results indicate that the rate and capacity for water sorption is strongly dependent on the chemical composition of the acrylic PSA films and structure of dried latex films, which can irreversibly change for various formulations with each moisture sorption-desorption cycle. The results also indicate substantial modifications to mechanical and performance properties with moisture uptake. The results provide valuable information for the design and processing of acrylic PSA products.