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November 2010




Big potential for nanoparticles in buildings


Due to their potential fire hazard, polymer-based building materials, other than paints, are traditionally not commonplace on a building site. If researchers at the CSIR have it their way, that is bound to change through the inclusion of clay nanoparticles.

“The addition of a relatively small amount of clay significantly improves the mechanical and material properties of polymers,” says Professor Suprakas Sinha Ray, chief researcher, polymer nanocomposites and leader of the CSIR-hosted National Centre for Nanostructured Materials (NCNSM), one of the Department of Science and Technology’s nanotech innovation centres.

“The comparison with pure polymer materials or conventional filler-filled composite materials is quite remarkable.” The “relatively small amount” that Sinha Ray is referring to is exactly that. Researchers at the NCNSM have shown that the inclusion of just 2% (in weight) of clay dramatically changed the inherent properties of composites – including paints and coatings. Among others, the paint and coatings become both UV and fire resistant, and it flows better or, as the scientists say, has “improved rheological behaviour”. “The nano centre is currently negotiating the transfer of the technology to a paint producer,” he says. Professor Suprakas Sinha Ray and Manfred Scriba from the National Centre of Nanostructured Materials

Small addition, major impact

According to Sinha Ray, researchers worldwide are giving a great deal of attention to the addition of nanoclay particles into polymer matrices to produce composite materials.

He explains: “This is because the nanoclay particles improve the properties of those materials. For instance, nanoclays can act as flame-retardant fillers by moving to the surface of the polymer, forming a coating that acts as a heat shield.

In addition, as shown by research at the NCNSM, chemically modified nanoclays may act as a binder  between otherwise un-mixable polymers.”

Manfred Scriba, a senior researcher at the NCNSM, comments on another way that nanoclays may impact on the building industry. “By manipulating the surface chemistry of nanoclay particles to facilitate proper dispersion and binding, we are able to convert plastic waste into advanced composite materials for housing components such as extruded window and door frames, and possibly even whole wall panels. The particles also act as a fire retardant. Furthermore, by including biomass such as wood or bamboo flour into the composite material, building costs as well as the carbon footprint may be reduced.”

The commonly-used clays for the preparation of nanocomposites belong to the same general family of 2:1 layered or phyllosilicates. These layers are about one nanometre thick. “The secret,” says Sinha Ray, “lies in the modification of the surface of these nano-layers or nanoplatelets so that the nano-properties come to the fore when incorporated in the paint or the plastic.”

Upscaling for industry

The NCSNM recently acquired a piece of equipment that will greatly assist scientists’ efforts in developing nanomaterials for industry use. This equipment, called a batch extruder, can produce 30 kg of composite per hour. “This will allow us to upscale laboratory-produced nanocomposites by producing small batches that can be tested in extruders and injection moulding processes in industry,” explains Scriba. The first product to follow this route will be bamboo and wood plastic composites intended for housing components. – Petro Lowies

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Article courtesy CSIR ScienceScope




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