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Construction : Material Advantage | October 2017 | Source : CW-India

Single-wall carbon nanotubes: Five times lighter but 100 times stronger than steel

Increasing customer demand for conductive floors has spurred Indian manufacturers to seek highly innovative technologies to upgrade conventional electrostatic discharge (ESD) flooring systems. Traditionally in India, static dissipative and conductive flooring was produced with carbon fibres, which provide acceptable results with only higher voltages. In contrast, single-wall carbon nanotubes (SWCNTs) provide floors with uniform and reliable electrical conductivity even at low voltages, more in line with newer standards. What's more, surface resistance remains uniform over time even with normal wear and tear, as Ravi Dabral, CEO, OCSiAl, explains.

How does it work? SWCNTs have a conductivity-to-weight ratio as conductive as copper but five times lighter; temperature resistance up to 1,000°C; and strength 100 times stronger than steel.
The dominance of SWCNTs centres on their extremely high ratio between length and mean outer diameter (around 2,500 times) and their flexibility, leading to an extremely low percolation threshold - an interconnecting 3D conductive network of nanotubes can be formed throughout the material matrix at extremely low concentrations, starting from just 0.01 per cent of the total weight. This loading is 100 times lower than that of any other conventional additive and enables conductivity, reinforcement of material, and vivid colours and light weight.

Overcoming challenges: While its benefits have been proven for many years, synthesising SWCNTs was, until recently, extremely challenging; only small quantities could be obtained at a high cost. Manufacturers of end-products were unable to use them in their production processes as there was no technology for mass production that could meet industrial demand and the price was prohibitive.

Is there an industrial technology for the synthesis of SWCNTs, scalable to hundreds of thousands of tonnes per year, and to reduce the cost by up to 100 times?
In 2016, Neocrete Technologies, an advanced manufacturer in the field of construction chemicals, epoxy flooring and waterproofing systems, began carrying out tests on conductive additives from two global companies. The most impressive results were achieved with the advanced conductive additive TUBALL based on SWCNTs produced by OCSiAl. The key advantage of TUBALL is that ultra-low dosages starting from as little as 0.01 per cent are sufficient to provide materials with uniform conductivity and enhanced mechanical properties. TUBALL nanotubes enable manufacturers to achieve conductivity along with various colours, better yield and performance in their ESD floorings. They contain over 80 per cent of SWCNTs.

In construction: Nanotubes have huge potential in the building, construction and infrastructure industries. For example, cement is produced in vast quantities around the world and contributes significantly to mankind's carbon footprint, but TUBALL can be used to make cement stronger, thereby reducing consumption and CO2 emissions and strengthening structures. Considerable research is being done in this field. TUBALL is often used in static-control floorings, carbon fibre-reinforced composites, epoxy adhesives, GFRP pipes, polyester gel coats, BMC and SMC composites, static-dissipative PVC, and other coatings. Striking results are being achieved in enabling conductivity and reinforcement, together with colouration of materials, leading to a wider application of SWCNTs and empowering engineers to develop lightweight products with versatility in design. Further, TUBALL helps in yielding more 'green points'. It is also proven to work in a paint that can dissipate heat uniformly and in smart windows.

- SERAPHINA D'SOUZA

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