Effects of surface tension reducing additive on surface morphology and wetting behavior of polyurethane coatings

Application of hydrophobic polymer coatings in protection of historical monuments as well as in anti-fog, anti-frost, anti-bio-fouling and anti corrosion surfaces, has drawn the attention of many researchers in recent years. Reaching this target needs to provide coating with low surface free energy and appropriate surface roughness. Controlling these parameters results in preparing surfaces with surface nature ranged from hydrophobic to superhydrophobic. The present study investigates the role of a surface tension reducing additive based on hydroxyl-functional silicone modified polyacrylate on the surface roughness and wetting behavior of polyurethane coatings. Polyurethane coatings with different amounts of additives were prepared. The coatings were cured at two different temperatures, i.e. ambient and 80˚C. Using atomic force microscope and contact angle measuring device the roughness and surface free energy of the samples were investigated, respectively. The results showed that addition of additive affected the roughness pattern of the surface as well as its chemistry. Furthermore, It was found that the roughness pattern of the coating was also influenced by the curing temperature. The largest contact angle (103˚) value was obtained when the coating loaded with 5 mol % of additive was cured at the ambient temperature. These suggest that this sample possesses the optimum chemical properties as well as the most appropriate roughness pattern.