The influence of repellent coatings on surface free energy of glass plate and cotton fabric

The aim of this research was to determine the influence of chemical finishes on the surface properties of glass plate, considered as a model homogeneous smooth surface and cotton fabric as a non-ideal heterogeneous rough surface. Microscopic slides and 100% cotton fabric in plain weave were coated with fluorocarbon polymers (FCP), paraffin waxes with zirconium salts (PWZ), methylolmelamine derivatives (MMD), polysiloxanes with side alkyldimethylammonium groups (PSAAC) and aminofunctional polysiloxanes (AFPS). From the goniometer contact angle measurements of different liquids, the surface free energy of the coated glass plates was calculated according to approaches by Owens-Wendt-Kaelble, Wu, van Oss-Chaudhury-Good, and Li-Neumann-Kwok. The results showed that all the coatings decreased the surface free energy of the substrate, which was also influenced by the liquid combination and the theoretical approach used. In spite of the fact that the liquid contact angles were much higher on the coated fabric samples than on glass plates and resulted in the lower values of work of adhesion, a very good correlation between the coatings deposited on both substrates was obtained. The presence of repellent coatings FCP, PWZ and MMD converted the solid surface from polar to highly apolar by masking the functional groups of glass and cellulose. PSAAC and AFPS coatings did not decrease the solid surface free energy to such an extent as the former three coatings due to their monopolar character.