Perfluorinated coatings and terracotta: An impregnation study

The mechanisms of penetration onto terracotta of two commercially available perfluorinated acrylates were studied: Zonyl®225, a solvent-based perfluorinated polyacrylate containing two unfluorinated acrylic or vinylic monomers; and Zonyl®329, an aqueous dispersion synthesized from comparable monomers plus a vinylic silane. Two application methods were used: by immersion of the substrate for 15 h and by multiple brush strokes, with pauses between strokes. Application effectiveness was assessed by measuring the depth of penetration into terracotta. The results of coating were examined by optical and electron microscopy, including elemental analysis. When the impregnating agent was applied by extended immersion, both solvent-based and aqueous dispersion exhibited higher penetration depths with increasing concentrations. When applied using multiple brush strokes, the solvent-based solution exhibited the same trend as that in immersion; however, the aqueous dispersion showed no penetration beyond 0.12 mm. This limited depth of penetration is shown to be a result of partial drying between brush strokes, but also as a result of porosity restrictions and electrostatic interactions between the positively charged polymer colloids in the dispersion and the negatively charged terracotta surface. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008