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Non-toxic foul-release provides an environmentally friendly and sustainable technical solution to control micro- and/or macrofouling on ships' hulls. Silicone-based coatings have been used for foul-release at high or moderate ship speeds (>15 knots). To remove the fouling from slower ships (<15 knots), the macrofoulers in particular, biodegradable polymers may be used to make the coating surface self-renewable. Synthesized by microorganisms for carbon and energy storage under controlled conditions, polyhydroxyalkanoates (PHAs) are hydrophobic biopolymers that are gradually decomposed into CO 2 and water in the environment. Because of their hydrophobic property and lack of hydrolysis in sterile aqueous solution, PHAs do not dissolve in water, but erode at the polymer surface (2-5 w m in depth) catalyzed exclusively by microbial enzymes (depolymerases) that are attached on the solid surface. The thin-layer surface erosion behaves like a self-renewable surface coating, which approaches a constant renewal rate at a relative hydraulic speed as low as 3 knots. A turbulence eddy model is used to describe the effect of energy consumption per mass of liquid on the turbulent shear stress and the surface renewal rate. Furthermore, the polymer biodegradation or surface renewal rate can be controlled within a broad range by blending the material with polymers such as poly ( l -caprolactone) (PCL). The biodegradation of binary blends of PHA/PCL of different compositions was quantitatively monitored by means of weight loss and Raman spectroscopy.
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