Is Young's Modulus a Critical Coating Property Determining Fouling-Release Performance of Marine Coatings?

Abstract

Marine organisms colonize all water-contacting surfaces. The accumulation of these organisms, known as biofouling, on ship hulls can increase fuel consumption by up to 45%, causing higher emissions. Remedy is offered by nonbiocidal fouling-release (FR) coatings, which weaken the adhesion between organisms and surfaces, enabling removal by hydrodynamic forces or gravity. This study investigates the FR performance of biocide-free polyurethane, polyurea, and silicone-based systems in relation to their Young's modulus. The rationale is to better understand the influence of Young's modulus across different polymer classes. Within these classes, Young's modulus varies in a narrow range (0.2–2.2 MPa) to study its effect on FR behavior. In polyurethane and polyurea systems, modulus adjustments are made by altering resin-to-hardener ratios, affecting crosslink density. Coatings underwent static immersion in the North Sea, and FR performance is monitored monthly. After 15 weeks, samples are cleaned with a high-pressure water jet. Compared to a hard reference system, all soft coatings exhibit FR performance identical to Intersleek 1100 SR after full immersion period and cleaning, highlighting the importance of mechanical softness for effective fouling release.