Correlation of mechanical properties with antifouling efficacy of coatings containing loaded microcapsules

Abstract

In this study, the antifouling efficacy of coatings containing loaded microcapsules made from gelatin and gum arabic, polyurethane, melamine-formaldehyde and a combination of the two first, is correlated with their mechanical properties. The nanoindentation technique is exploited for this reason, for the assessment of six antifouling coatings that have been exposed in the sea for nine months, in order to find a correlation between their antifouling functionality and their mechanical response. From the nanomechanical measurements, functional properties such as stiffness, wear resistance, elastic and plastic deformation, were extracted and connected to the antifouling performance of the coatings (leached layer, erosion rate, self-polishing properties, functionality maintenance). In parallel, surface characteristics were examined though optical microscopy, in order to detect defects and surface morphology that may affect the measurements. The antifouling efficacy was assessed with three different endpoints; biomass, chlorophyll a quantification and surface coverage. The above resulted to a classification of the novel antifouling coatings containing microcapsules, in terms of their antifouling performance and mechanical robustness. The results were also correlated with the release rate of the encapsulated biocide and compared with its addition in free state. It was concluded that the coating containing gelatin-gum arabic capsules had the best antifouling performance but not acceptable mechanical properties, whereas the coating containing polyurea capsules had both satisfying antifouling efficacy and improved mechanical properties compared to the control sample.