Coatings are important in their ability to protect valuable assets. For Naval vessels, coatings having specialized functions are also essential. For example, coatings are needed to mitigate the effect of biofouling on ship hulls. Ships operating in northern latitudes may suffer from ice accumulation which can be addressed using ice releasing coatings. Using the concept of self-stratification, it is possible to decouple the surface and bulk properties of coatings so that the bulk and surface properties can be tuned individually to meet the material requirements. The approach of self-stratification has been applied to the design of mechanically robust marine fouling-release coatings. By combining functional poly(dimethyl siloxane) (PDMS) with a polyurethane system, coatings having the bulk properties of polyurethanes (good adhesion, toughness) as well as low surface energy can be designed that have good fouling-release performance for a wide variety of marine organisms. However, there are some marine organisms that are able to adhere well to a low surface energy surface such as PDMS. To overcome this an amphiphilic approach has been investigated. Siloxane-polyurethane coatings containing PDMS and poly(ethyleneglycol)(PEG) were made. The coatings were characterized using contact angle measurements, AFM, and XPS. The coatings were also subjected to a series of laboratory assays using a variety of marine organisms including diatoms, green algae, barnacles, and mussels. Clear trends could be observed in the barnacle adhesion as a function of PDMS and PEG chain length and coatings having good fouling-release performance for a variety of marine organisms were identified. The coatings were also subjected to ice adhesion tests and a very interesting and rather direct correlation was observed between the adhesion strength of ice and barnacles, indicating that the same design rules for designing fouling-release coatings could be applied to the design of ice-release coatings.

Designing durable coatings with low surface adhesion for mitigation of fouling and ice adhesion

2019 Fall National Meeting

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