POSS functionalized with mixed fluoroalkyl and methacryloxy substituents as modifiers for UV-curable coatings

Abstract

UV-curable acrylate-based coatings were modified by copolymerization of base resins with polyhedral oligomeric silsesquioxanes (POSS) containing four methacryloxy and four fluoroalkyl substituents in one molecule (4M4F-POSS), giving hybrid organic–inorganic coatings. Such modifiers are covalently linked to the matrix (by methacryloxy groups) preventing them from exuding onto the surface, and fluoroalkyl substituents (along with the POSS cages) improve scratch resistance and hydrophobicity. Two types of POSS derivatives differing with the length of the fluoroalkyl chain were tested. These compounds were applied in two types of formulations: wood-derived and aluminum substrates. Modification of the coatings led to a substantial increase in the hydrophobicity and enhanced scratch resistance after incorporation of only 1.5 wt% of the modifier. Water contact angle increased by up to 14–160% of the initial value, whereas the scratch hardness for the first surface stripping improved by about 30–170% in the presence of 5 wt% of POSS. The latter can be associated with the increase in the surface sliding properties caused by the presence of fluoroalkyl substituents of the modifier. Better results were obtained for POSS containing shorter fluoroalkyl substituents.