Compositional effects on the fouling resistance of fluorourethane coatings

Conclusions  A series of fluorinated polyurethane polymers have been prepared and characterized. Immersion experiments have been performed to determine the fouling-release effectiveness of the coatings. The surface energies of the films are between 12 mJ m⁻² to 33 mJ m⁻² and are controlled by the fluorine content of the polymer. These surface energies are well below the values shown by conventional alkyd, epoxy, vinyl, polyester, and polyurethane coatings (39 mJ m⁻² and 50 mJ m⁻²). Surface energy is not the dominant factor in determining the fouling- release behaviour of these coatings. Instead, measurements of the coating modulus, hardness, and glass transition temperature indicate that supple, soft polymers, with a high degree of mobility may display more effective fouling-release characteristics than more rigid, harder polymers below their glass transition temperatures. Surface roughness also appears to be a major factor in determining coating fouling-release behaviour. This work has demonstrated that marine organisms bind to fluorinated polyurethanes with significantly less strength than to the unfluorinated epoxy, vinyl and urethane resins which are now used with toxicants in marine coatings. However, this work has shown that these fluorinated polyurethanes are not sufficiently promising to merit further attention as non-toxic anti-fouling coatings for ship hulls. Fluorinated polyurethanes remain very attractive coatings for exterior and anti-corrosive service, especially in application requiring easy cleanability and resistance to sunlight, weather, and chemicals.