Advances in design and manufacturing of environmentally friendly and biocide-free antifouling/foul-release coatings: replacement of fluorinate species

Abstract

Amphiphilic coatings are nowadays described as the most promising strategy for the achievement of an effective and eco-friendly antifouling marine paint, based on a physical principle. Nevertheless, most of the preparations imply the introduction of fluorinate chemicals for the formation of the hydrophobic moieties, which are potentially toxic for the marine environment in the case of an accidental release. The present work evaluates the possibility of removing fluorinate species for the implementation of such coatings and their replacement with analogous long-alkyls. In particular, this work presents an easily implementable procedure for the manufacturing of an amphiphilic system that exploits the reactivity of a commercially available –OH-rich hybrid polysiloxane resin. The resin was first modified through sol–gel chemistry that was used in the grafting of a silane-bearing hydrophobic long-alkyl chain, while the introduction of the hydrophilic moieties was conducted contextually to the curing process, through the reaction with a commercially available PEG-ilate isocyanate hardener. The effective persistence of the amphiphilic character with respect to the replacement of the fluorinate silane by the alkylsilane was ensured by the measurement of the hysteresis contact angle. The effectiveness of the persistence of the antifouling/foul-release properties was assessed through testing against the adhesion and deposition of egg white, as a proteinaceous probe, Mytilus edulis (mussel) and Ulva intestinalis (algae). All the tests indicated that the amphiphilic coating prepared from long-alkyl silane performed even better than fluorinate silane-containing samples in this hybrid coating system resulting from the fusion of a xerogel and a resin. The results suggested that the use of a long alkyl silane was an effective alternative to the use of potentially noxious fluorinate silanes, with advantages that boost the ecological benefits and also include the performance of the coating.