Shipping accounts for at least 90% of the global trade of goods. In terms of distance travelled, shipping is by far the most efficient method of transporting goods. The biggest problem in this method of transportation is the biofouling on ships hulls. Marine biofouling is caused by the adhesion of barnacles, macroalgae and microbial slimes. On ships hulls, biofouling results in an increase in roughness, which in turn leads to an increase in hydrodynamic drag as the vessel moves through water. Enhanced fuel consumption, hull cleaning, paint removal and repainting, and associated environmental compliance measures all contribute to the costs of biofouling. New, effective, and environmentally compatible options are needed to control fouling. One critical point in the development of such paints is that the outer surface has to exhibit certain properties in order to repel fouling microorganisms, such as superhydrophobic behavior and reduced drag force.
The product introduced in this work represents a key enabling technology for manufacturers to maximize profit and gain competitive advantages. Silicone based coatings were prepared with multi-wall nanotube (MWCNTs) of extremely low bulk density that enables efficient dispersion in resins. The goal was to create superhydrophobic surfaces that can also exhibit fouling release properties. Besides the use of pristine nanotubes, chemical functionalization of MWCNTs also took place for comparison purposes as well as graphene-based additives. Different protocols for the nanostructured coatings preparation were also investigated.
The obtained surfaces were fully characterized in terms of hydrophobicity as determined by contact angle measurements. Higher elongation and remarkably improved mechanical strength were concurrently achieved, with respect to the pure resins, thus expecting to lead to increased coating lifetime. The mechanical properties of the pristine MWCNTs were more enhanced than those of functionalized nanotubes, indicating that the production of the novel coatings can be cost effective if the synthesis of MWCNTs has been properly tailored.
The coatings with the most promising results (contact angle > 100°) were immersed in static seawaters to visualize any incurred fouling phenomena as a function of time. Results on the MWCNTs-silicone formulations that resulted in the best fouling release performance are discussed and compared with results from previous related work using other resin matrices. It should be pointed out that the developed coatings do not contain any harmful for the marine ecosystem biocides as the 2nd generation antifouling coatings available in the market. The fouling release properties of the coatings result from the needle-like structure of nanostructured carbon that can facilitate release of microorganisms responsible for biofouling.
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