Engineers develop spray to make clothes more fire-resistant

Researchers at UNSW have developed a novel fire-resistant spray that could slow the rate at which cotton materials catch fire—and reduce the risk of burning.

Designed with everyday materials in mind, like shirts or bedding that most people have at home, this new formula could offer vital protection to those living in bushfire-prone areas or in emergency situations.

The water-based spray coats fabric with a virtually invisible layer of protection without altering the fabric’s softness or breathability, a common challenge when applying coating on textiles.

Professor Guan Yeoh and his team of researchers from UNSW Mechanical and Manufacturing Engineering have spent the last two years working on the formula. They are experts at creating fire-resistant products—in 2023 they created FSA Firecoat, a fire-retardant paint which was the first in Australia to pass the BAL-40 test and now sold at Bunnings.

“We chose cotton because it’s one of the most common materials used in the clothing and textile industry,” he says. “What we’ve achieved is a solution that doesn’t smell and doesn’t change the softness of the cotton once it’s sprayed on. So, the item of clothing still feels the same as before.”

From plants to protection

The formula uses non-toxic ingredients consisting of phosphorus and nitrogen elements, which act as the binder, and a water-soluble cellulose extract, a plant-derived organic compound rich in carbon that can be found in cotton, wood pulp, or other plant biomass.

When combined, they form a thin protective coating that binds firmly to natural fibers like cotton. The phosphorus tightens the carbon layer which repels the heat.

“In the final formulation, we only use a concentration of about 10% to 15% to make it easier to spray onto surfaces—and dries instantly too,” says Prof. Yeoh, Director of the ARC Research Hub for FRIASA at UNSW.

“This results in a fabric that resists burning and significantly reduces heat transfer, without stiffening or any noticeable color changes.

“And since the bottle is completely sealed to prevent oxidation, it has a very long shelf life. If the bottle is kept tightly sealed, we can expect it will last more than a year.”

An effective fire safety layer

In laboratory tests, two pieces of cotton, one sprayed with the coating and the other untreated, were exposed to a direct flame. The researchers found that coated fabric took twice as long to ignite and released half the heat compared to the untreated fabric.

The flame also only charred the treated fabric whereas the untreated fabric burnt into flames in seconds.

The test also showed a peak heat release rate (PHRR) reduction of about 89%, meaning the treated cotton material produces only 11% of the maximum heat output of the untreated sample.

Lowering the PHRR is critical to slowing down the rate fire grows, reducing heat intensity, and lowering the chance of a material igniting almost instantly.

“Our results also show that when exposed to heat, the surface temperatures on the textiles could be reduced to 30% to 40% of the heat temperature,” says Prof. Yeoh.

“In simulated fire environments, treated fabrics kept temperatures on the skin-side below 40°C, even when the external environment hit 100°C.

“It’s like standing in boiling water versus feeling warm—that difference could prevent scalding or burns to the skin.”

One of the key advantages of the spray is the durability of the solution—it’s strong enough to withstand light contact with water but will completely dissolve in a rigorous wash.

To test this, the team washed the treated fabric and exposed it to a flame. It burned just as quickly as an untreated fabric.

“What we wanted to demonstrate was whether washing off the coating would return the fabric to its original flammability,” says Prof. Yeoh. “And it did, which shows that the coating provides that protective layer on your shirt or pants until you wash it off.”

Next steps

Partnering with AI solutions company N2N AI, Prof. Yeoh says he expects to see this product available commercially within the next year.

“There are still a few hurdles to clear, but the biggest one, fire performance, is already behind us,” he says. “The formulation consists of non-toxic compounds with a neutral pH of 7 and, in our tests, we didn’t observe any skin irritations when sprayed in low doses. However, we still need to do further dermatological testing to fully understand its effects on the skin.

“We’re also testing the formulation on other materials such as polyester—which has already shown promising results.”

Prof. Yeoh and his team are also careful not to oversell the solution. “It’s an added layer of protection, not a magical force field,” he says. “If someone is alone, it might be tricky to spray their back—just like applying sunscreen.

“And we’re not saying this will make people completely fireproof but it can slow down the rate of your clothes burning—and potentially reduce injury in a fire.

“That delay could be crucial in emergencies, offering precious seconds to escape.”