Nanoclay can stop cladding fires spreading

Tiny particles of “nanoclay” added to building cladding can radically reduce the risk of fires spreading, preventing future disasters like the Grenfell Tower blaze in London.

The Grenfell fire focused world attention on the dangers of plastic-backed aluminium cladding that is being blamed for the speed at which the fire spread, engulfing the 24-storey building. At least 80 people are dead, presumed dead, or missing.

But research by University of Melbourne engineers has found that adding nanoclay particles to plastic cladding can drastically reduce the heat and smoke that is emitted as it burns. And crucially, non-metal composite cladding treated with nanoclay doesn’t spread the fire during burning, allowing time for people to evacuate and for fire fighters to tackle the blaze.

“During a fire, as the cladding heats up, these small particles of clay react and form an insulation barrier over the polymer plastic, protecting it from the heat and flame,” says Dr Kate Nguyen, Leader of the University’s Innovative Fire Engineering research group. “It effectively creates a “ceramic-like” barrier.”

In the wake of the Grenfell fire Australia’s Victoria state has appointed a taskforce to fast-track its investigation into flammable cladding that followed the 2014 fire at the Lacrosse Building in Melbourne that is similarly covered in combustible aluminium-backed cladding.

The particles of nanoclay are just 5 nanometres thick – that is 0.000005 millimetres. Laboratory test results found that glass-fibre cladding material with the nanoclay particles reduced heat and smoke emissions by 40 per cent, and prevented the fire from spreading.

Dr Nguyen’s research on nanoclay as a flame retardant goes back to 2011 as part of an Australian Research Council linkage grant led by Associate Professor Tuan Ngo in which she was working with a façade company to improve the fire safety of Glass Fibre Reinforced Polymer Cladding. It is the first time that nanoclay has been used to improve the fire performance of cladding. Dr Nguyen says the new material developed in this project could be used to manufacture cladding which is both safe and more attractive to builders and architects because it is more flexible than metal-backed cladding and can be used in more varied designs.

GFRP is constructed of glass fibre compacted together with an adhesive polymeric resin. It is this resin that is highly flammable. It means producers currently have to add large quantities of expensive fire-retardant powders that can limit the strength of the cladding. But Dr Nguyen and her colleagues found that only small quantities of nanoclay are needed to significantly reduce the fire risk to this type of cladding.

“It will still burn, but it won’t produce the same heat and any fire won’t spread,” says Dr Nguyen. While there are non-combustible mineral cladding alternatives on the market, she says these are heavier and less architecturally flexible.

The research involved extensive testing of different nanoclays to find clay that would combine properly with the resin. “Like oil and water, some of the clays just didn’t mix well with resin,” says Dr Nguyen. They eventually settled on a clay called organoclay that is compatible with the organic resin.

Subject to further large scale testing, Dr Nguyen says the nanoclay-treated cladding should be considered as an effective way to retro-fit the external cladding of buildings covered with metal-backed plastic cladding.

Australia changed its building code to ban the use of combustible materials in the wake of the Lacrosse apartment building fire that was spread by plastic-backed aluminium cladding. While no one was seriously injured in the fire, which was started by a lit cigarette on a balcony, the aluminium backing transferred the heat upwards setting the apartments above on fire as the plastic combusted. However over half of Melbourne’s high-rises were already covered with non-compliant cladding and remain that way now.

“We have to change the facades on these buildings if we are to make them safe, and nanoclay materials could be the way to retrofit them,” says Dr Nguyen.

Dr Nguyen and her colleagues Associate Professor Ngo and Professor Priyan Mendis will be speaking on at free public lecture at the University of Melbourne – “The Aftermath of the Grenfell Tower Fire – Are Australian buildings safe?” on Tuesday July 4. The key speaker is fire expert Jonathan Barnett, Technical Director of RED Fire Engineers.

Banner: Tower block on the Chalcots Estate in London, June 26, 2017, where some towers are being evacuated after they were found to have similar cladding to that on the Grenfell Tower. Picture: Dan Kirkwood/Getty Images.