Nanotechnology making yachts greener
by Richard Boggs
Conventional antifouling techniques are based primarily on two approaches: paint that contains dispersed particles of organocopper compounds that are poisonous to marine organisms attempting to cling to the yacht’s hull, and non-stick coatings that prevent organisms from gripping the hull’s surface.
Biocidal formulations are being phased out (i.e. the now-banned tributyltin bottom paint) because the compounds used can be lethal to other marine life, even in extremely low concentrations. But because nanoparticles can tightly lock biocidal compounds to their surface, they can be encapsulated within or bound to the surface of the lattice of what are called ‘dendritic nanostructures’.
When these structures are combined with non-stick or slippery antifouling coatings, the biocidal action occurs only when an organism is in direct contact with the tightly bound compound. The release of toxic chemicals to surrounding seawater is virtually eliminated, while highly effective antifouling properties persist for much longer periods than existing systems.
This same property of electronic attraction and crack filling used in paint applications make it possible to use nanomaterials to produce nanocomposites with structural qualities that far exceed conventional layups.
Columbus, Ohio-based Zyvex Technologies proved the concept by building an Unmanned Surface Vessel for the US Navy using carbon nanotube-reinforced carbon fibre composite construction.
According to the builder, the 8,400-pound vessel would have weighed more than 40,000 pounds if constructed using conventional fibreglass techniques. This weight reduction alone reduced the fuel consumption from an estimated 50 gallons per hour for the glass version to 12 gallons per hour at 25 knots.
The use of nanotube reinforcement is credited for this 75 per cent weight reduction while also improving the structure’s strength and durability.
The same properties that give nanoparticle-containing coatings “self healing” properties provide nanocomposite materials with remarkable abilities to resist the stress cracking often seen in areas of stress concentrations on conventional fiberglass construction.
On a larger scale, strong electrical bonds between nanoparticles resist potentially damaging cyclic loads. This process effectively counters the forces that otherwise would cause delamination or cracking, and it’s this characteristic that allowed Zyvex to reduce structural weight to such a large degree without sacrificing strength or durability.