Abstract
The surface energy of coating layers influences their final properties such as their ability to repel or absorb fluids. Recent work has shown that the substrate, due to absorption, can alter the surface chemistry of the top coating layer. However, the influence of substrate properties on coating surface energies is not reported in the literature.
Three coatings, based on a pigment and a latex binder, are applied on three different substrates that differ in terms of absorption properties. The three coatings were also modified with a soluble polymer. Contact angle measurements of three different probe fluids were measured. These contact angles were used to estimate the polar, dispersive, and total surface energy of the coating layers. Surface energies were also determined for the latex and pigments.
The contact angles and surface energies of the latex films and pigments agree with the expected results. Most of the results for the coating layers agree with the reported surface chemistry of these coatings. Large pigment systems on absorbent substrates have a high contact angle and low surface energy. These results agree with the expected results based on the surface chemistry reported in past work. The results for the fine pigment system had low contact angles and high surface energies and did not agree with the expected results. The contact angles may be influenced by the surface roughness of the coatings or the expected surface energy of a heterogeneous surface may not be a simple function of the surface composition.