Development of a measuring method for characterizing the surface of Pressure Sensitive Adhesives (PSA)

Hydrophobic Recovery and Wilhelmy measuring method with acrylic-acid-based products The characterization of the surface properties of Pressure Sensitive Adhesives (PSA) is an important part of the product development and optimization. Variable concentrations of the acrylic acid content enable the surface polarity to be adjusted to suit the particular substrate. We have evaluated tensiometric contact angle measurement as an alternative to the optical sessile drop method based on acrylate-based PSAs with different acrylic acid content. This method was shown to be well suited and has advantages compared with the optical method. The dynamics of possible reorientation of the surface functional groups in the PSA were investigated as part of a long-term study of the water and diiodomethane contact angles of samples conditioned in water. Our results indicate that the timescale for such Hydrophobic Recovery lies in the range with an order of magnitude of less than one minute. The advancing angles with water show a linear relationship with the acrylic acid content of the PSA. Wilhelmy CA measurements are therefore well suited for adjusting changes to the surface polarity caused by the variable acrylic acid content.