Surface resistivity as low as 10^3 Ω/sq in polyester-based gelcoats is achieved by adding a tiny amount of TUBALL nanotubes, also enhancing surface appearance and weathering resistance.
“Application of carbon black or graphite as a conductive additive negatively affects the original colour, resulting in a black surface, or dark grey at best,” says Elmar Greiff, Project Leader Nanocomposites, BÜFA Composite Systems. “That strong correlation has resulted in the stereotype about conductivity always being associated with a black colour. However, switching to TUBALL nanotubes, produced by OCSiAl, has enabled us to overcome this drawback. We now make conductive gelcoats with previously unachievable colour shades, including almost white. For instance, we produce translucent conductive gelcoats with a surface resistivity of just 10^3 Ω/sq.”
Even ultra-low loadings of TUBALL single wall carbon nanotubes are enough to achieve the required permanent and stable conductivity, reports OCSiAl. This leads directly to a number of additional performance benefits, such as a smooth and homogeneous surface, without the negative influence on weathering that is usually associated with carbon black or graphite. Furthermore, the nanotubes are supplied in the form of a paste that allows customers to handle them with standard application methods without any additional equipment.
“We acknowledge the high and rapidly growing market demand for gelcoats containing nanotubes,” adds Greiff. “A number of end products that use our gelcoats have already successfully hit the market.”
According to OCSiAl, there are some applications where nanotube-based gelcoats can almost completely replace standard gelcoats, for example in tooling gelcoats. Due to the triboelectric effect, a static discharge can occur when a GRP part is demoulded. Even a minor flash can cause an explosion at a facility if there are any flammable materials nearby. BÜFA Composite Systems has developed a tooling gelcoat with TUBALL nanotubes. Its surface resistivity of 10^6 Ω/sq is low enough to prevent any accumulation of electric charge. Another advantage of such anti-static coatings is that they stop the surface from attracting the dust that would otherwise result in shorter working cycles and longer mould preparation times.
Conductive gelcoats with TUBALL single wall carbon nanotubes are also said to be finding application in pipes and tanks for chemicals, ventilation systems, printing rollers, control boxes for electronics, floor coatings at industrial production plants, and resins for composites.