Sustainable Graphene Nanotube Solutions

Advanced coating safety, durability and performance through sustainable graphene nanotube solutions

Graphene nanotubes produced by OCSiAl under the trade name TUBALL demonstrate superior performance compared to standard conductive additives. This performance is made possible by the groundbreaking properties of this technology. Graphene nanotubes are graphene sheets wrapped around tubes with a wall thickness of a single carbon atom, approximately 1.2–2 nanometres in diameter and approximately 5 micrometres in length. This material possesses an extremely high aspect ratio and length-to-diameter ratio, resulting in the unique morphology and performance of graphene nanotubes. Graphene nanotubes are among the world's strongest materials with high electrical conductivity and are extremely flexible. When uniformly dispersed, they allow reaching target conductivity and improving mechanical properties even at dosages tens or hundreds of times lower than other conductive additives. Thus graphene nanotubes enable manufacturers to create entirely new materials with all the required properties on the market. Now let us explore the specific properties that graphene nanotubes develop in different types of industrial coatings.

Light-coloured conductive tank linings for safer and lower-cost storage and transport

Unlike standard anti-static additives, graphene nanotubes guarantee stable and uniform electrical conductivity providing increased safety. Ultra-low working dosages open the door to light-coloured lining coatings while providing faster and easier routine inspections. Many companies have already approved TUBALL™. The experience of one European customer shows that 20–30 per cent by weight of conductive mica in various epoxy coatings can be replaced with only 0.03 per cent by weight of graphene nanotubes. This small amount is sufficient to provide a constant and permanent surface resistance of 104–108 Ω/sq, maintain superior bond strength and adhesion, high resistance to wear, abrasion and impact, and avoid time-consuming, costly repair maintenance.

Specific industrial immersion test successfully completed

Tank lining coating with TUBALL™ nanotubes passed resistance tests for crude oil, petrol, ethanol and water. The new anti-static lining with graphene nanotubes is used in storage tanks for crude oil, fuel, diesel oil, jet fuel, motor petrol and similar liquids. In addition to tank linings, it can also be used for tankers and containers in transport, chemical processing, electronic manufacturing, pharmaceutical and other applications. Graphene nanotubes provide permanent properties that are not dependent on environmental conditions such as moisture. The electrical conductivity properties provided by the nanotubes will persist throughout the service life of the tank lining coating.

Conductive flooring for ESD protection with maintained appearance and durability

The second application where replacing standard additives with graphene nanotubes provides visible added value is self-levelling floors. The addition of graphene nanotubes allows imparting stable and homogeneous anti-static properties to floors while preserving the important strengths of epoxy floors such as good durability, wear resistance and colour flexibility. A Switzerland-based company has developed an ESD-compatible top flooring coating for static-sensitive areas by adding only 0.01–0.05 per cent by weight of graphene nanotubes. Regardless of moisture, the floor and surface-to-surface show persistent and homogeneous resistance of 104–1011 Ω/sq without hot spots and black spots. Graphene nanotubes provide unparalleled performance compared to standard anti-static additives. They enable preserving and even improving the mechanical wear, impact and chemical resistance, water and dust impermeability of the host material. At ultra-low doses, graphene nanotubes can replace up to 4 per cent of chopped carbon fibres or 30 per cent of mica without modifying the basic formulation of the flooring compound and without additional costs. The low working dosage of nanotubes prevents the colour pigment from overlapping with the typically required high anti-static additive loading and avoids dark tones in the final coating. This new product has been developed to meet the highest demands of system shoe – floor primary grounding in compliance with ASTM F150 standards (106 < R ≤ 109 Ω), EN61340-4-1, ANSI/ESD S7.1 (RG < 109 Ω). Typical applications in this field include manufacturing, assembling, installing, packaging, testing or transporting industries such as clean rooms, pharmaceuticals and automotive.

In-line e-coating of plastic and metal exterior parts made possible through conductive acrylic primers

Graphene nanotubes added to acrylic automotive primers with very low surface resistance and high adhesion properties enable the application of base coatings and other coating systems to automotive plastic exterior parts using a low-cost method: electrostatic application. This is possible because conductive acrylic primers for polypropylene parts with graphene nanotubes show a constant, homogeneous surface resistance level of approximately 105 Ω/sq. Primers with an L-value between 67–75 per cent can be produced starting from 0.01 per cent by weight with the required nanotubes concentration. This becomes apparent when the same base coat thickness is applied over dark grey carbon black-based primers and light grey graphene nanotube-based primers. The L-value of the nanotube-based sample is much higher. As a result, base coat consumption can be reduced by lowering costs for the entire formulation. Today it is possible to create conductive primers not only for PP bumpers but also for SMC exterior parts. Initial trials have shown that instead of putting the part through cataphoresis (e-coating), it is possible to assemble the SMC part coated with primer and metal body, then dry in an oven and finally apply base coat using the electrostatic method. Direct painting of exterior parts onto the conveyor in this manner represents a significant advantage for OEM manufacturers.

A shortcut to adding conductivity to powder coatings

Powder coatings with good surface quality and simpler application processes are possible with graphene nanotubes. In this regard, a Slovenian company developed anti-static powder coating for automotive applications. Graphene nanotubes provide permanent, stable and homogeneous surface resistance of 106 Ω/sq without insulating spots and moisture dependency. Another leading producer in the field has developed various powder coatings using OCSiAl's TUBALL graphene nanotubes. The new products exhibit both conductive and static energy dissipating properties with resistance ranging from 103 Ω/sq to 109 Ω/sq. Initial laboratory tests have shown positive results in combining target conductivity with aesthetic performance on various surface textures and colours. Sprayable electrically conductive powder coatings with graphene nanotubes, compatible with most engineering plastics and metal substrates, are welcomed in electrostatic-sensitive applications in ATEX hazardous environments, instrumentation, medical, maritime, aviation and defence industries.

Material development to achieve carbon neutrality

The use of sustainable solutions based on graphene nanotubes increases production cost efficiency and contributes to reduced CO2 emissions. The low working dose of nanotubes enables doing more with less, meaning less raw material is required to create higher-performance products. The sustainability of the coating is facilitated by the reduced environmental impact of the nanotubes due to the long-term durability of the coating.   Andrew Dubrovskiy Technical Sales Manager Coatings and Thermoplastics / EMEA OCSiAl Group