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.
