WENDT, D.E.; KOWALKE, G.L.; KIM, J.; SINGER, I.L.; Cal Poly, San Luis Obispo; Cal Poly, San Luis Obispo; US Naval Research Laboratory; US Naval Research Laboratory: Factors that Influence Elastomeric Coating Performance: The Effect of Coating Thickness on Growth, Critical Removal Stress, and Modes of Release of the Barnacle Balanus amphitrite

Silicone-based coatings are currently the most efficacious non-toxic fouling release surfaces. Understanding the fundamental mechanisms that contribute to the performance of silicone coatings is necessary to further improve their design and functionality. The primary objective of this study is to examine the effect of coating thickness on growth, critical removal stress, and modes of release of the barnacle Balanus amphitrite. Animals were grown on �pure� PDMS (Gelest) surfaces that were 0.1 mm, 0.5 mm, and 2.0 mm thick. We found no difference in growth rate or size of individuals as a function of coating thickness. We observed abnormal basal plate and adhesive plaque morphology, although there was no predictable relationship between coating thickness and the frequency of occurrence. We found that critical removal stress was inversely proportional to coating thickness. Moreover, individuals with an abnormal basal plate and adhesive plaque morphology had a significantly lower critical removal stress than individuals with the normal adhesive plaque. These data suggest that the functionality of the adhesive has been compromised in individuals exhibiting the unusual adhesive plaque. The mode of release of animals from coatings also showed a dependency on coating thickness. For thick coatings the mode of release was a broad peel front that led to detachment, whereas removal on thin coatings occurred by localized peeling and coalescence. Taken together, our data demonstrate that coating thickness is an important fundamental factor governing removal of barnacles from non-toxic silicone coatings.