New antifouling (AF) coatings were designed and manufactured exploiting the proven foul-release (FR) properties of amphiphilic systems and comparing them with fully hydrophobic and hydrophilic systems. The novel strategy implied a simple synthesis route that involves exclusively the chemistry of polyurethanes. The system was indeed constituted by a corrosion resistant polysiloxane-polyester hybrid resin as binder, rich in highly reactive hydroxyl groups that make the polymer associable to the polyol of a polyurethane couple. Hydrophilic and hydrophobic moieties were introduced in the form of lateral chains of isocyanate hardeners. The system resulted easily implementable due to the combination of commercially available raw materials and the rapid kinetic of the reaction. This method was used to prepare amphiphilic, as well as fully hydrophilic and hydrophobic systems, which were spray coated on construction steel samples. The coating wettability was analysed on all samples through the measurement of wetting hysteresis, highlighting the amphiphilic behaviour of the formulations. The highest amphiphilic character was detected on the hydrophilic reference sample, probably due to the highest mobility of PEG-ilate chains under this configuration. Anti-fouling properties were determined by the evaluation of the retention rate of two alive Mediterranean marine organisms, Mytilus Edulis and Ulva Intestinalis, on the surface of samples. A further test was carried out to evaluate the AF/FR properties against a natural protein probe, namely egg white. The test carried out with natural organisms proved the suitability of all the proposed strategies to the implementation of effective AF/FR marine paints. The egg white test assessed that the highest efficiency in AF/FR activity was detained by the fully hydrophobic systems. The observation of the surface of the samples by SEM in back scatter modality revealed that the chemical patterning of the hydrophobic scenario could play a significant role in the development of such behaviour.
Barletta, M., Aversa, C., Pizzi, E., Puopolo, M., & Vesco, S. (2018). Design, development and first validation of “biocide-free” anti-fouling coatings. PROGRESS IN ORGANIC COATINGS, 123, 35-46 [10.1016/j.porgcoat.2018.06.007].