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Study finds wool is best for fire resistant material

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Australian Wool Innovation (AWI) is a nonprofit dedicated to conducting research, development and marketing of the worldwide supply chain of Australian wool to increase the long-term profitability of Australian woolgrowers. 

            A recent AWI-funded study proved wool and wool-rich fabrics, used as base-layer garments for military and first responders such as firefighters, were the best materials for fire resistance.

Although the study was conducted with Australian producers in mind, this is big news for a state such as Wyoming, who sends 70 percent of their wool to the military, according to Wyoming Wool Growers Association Executive Director Amy Hendrickson. 

Increased demand for base-layer garments

            Wool’s inherent ability to protect wearers from hostile environments, including extreme cold and fire, has made it the military’s fiber of choice for many years. Today, the military and first responders are increasingly interested in base-layer wool garments as a ‘”last line of defense.” 

            “This growing market demand for wool base-layer garments relates to the already well-researched benefits of super-fine Merino wool, including its softness next to the skin, moisture management, breathability and fire resistance,” said AWI’s Program Manager for Fiber Advocacy and Eco Credentials Angus Ireland. 

            AWI notes the increased demand has been driven, in part, by the incidence of injuries to military personnel in the Middle East, where battle techniques such as improvised explosive devices (IEDs) are used. 

Comparing fiber types

A review in 2017 of base-layer undergarments worn by the military, fire service, police and first responders by AgResearch revealed there are often no required specifications of test method standards relating to these protective garments.

 “This results in cotton or synthetic base-layers often being chosen by some military and emergency service personnel,” states AWI.

AWI notes cotton is often a popular choice of material because it is cheaper and cotton is often perceived as being cooler than wool. 

“However, there is a risk of large amounts of sweat and moisture building up in cotton garments when worn in a layered system, which at high heat intensities increases radiant heat transfer and can lead to steam burns and increased levels of stress,” explains AWI.

“There is also a trend to choose synthetic moisture wicking sportswear garments,” AWI states. “The key concern with synthetic fibers, even flame retardant ones, is when exposed to flame or extreme heat, they melt and drip, which can result in molten polymer burning the wearer’s skin.”

“In contrast, wool fibers are known to have a natural resistance to burning, even when exposed to an ignition source for long periods of time. This is due to wool having a high ignition temperature, high limiting oxygen index and its self-extinguishing behavior,” Ireland says. 

The study

            Because of this, AWI decided to fund a study, conducted by AgResearch, to compare the fire resistance of these materials.

            AWI notes fire resistance of nine different fabrics used as base-layer garments for military and first responder personnel was tested. To enable a realistic assessment of the protection offered by the base-layer garments, a new ‘skin simulant’ test method was designed using fresh pig skin.

            The test method involved two techniques to simulate the skin’s exposure – a naked flame ignition source and an accelerant fuelled threat, such as an IED or petrol bomb.

            “Once cooled, the most visibly damaged area of skin for each test was sampled and examined using a microscope,” explains AWI. “The results showed the worst performing fabric was 100 percent synthetic fibers, such as polypropylene fabric.”

AWI also notes the fabric that performed best overall was the 100 percent Zirpro-treated wool fabric, which showed no apparent differences compared to the undamaged control samples in both the naked flame and accelerant tests. 

The second-best performing fabric was double-knit blend of Merino wool and fire resistant treated viscose. 

There was a three-way tie for the third ranking fabrics, which included a rib-knit blend of Merino and fire resistant treated viscose, a blend of Modacrylic, raylon and nylon and Nomex fabric.

Ireland says these results show there is significant potential for wool base-layers to be used for protection as well as comfort by the military and emergency responders.

“The new test method demonstrated that while synthetic fabrics might be the most cost effective with regard to procurement, they offer very little protection to the wearer under the applied test conditions,” Ireland says. “It also highlights an expensive fiber such as Nomex is not the only option for protection, as the wool and viscose blend fabric of comparable density can offer the same or better levels of protection.”

Hannah Bugas is the managing editor for the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.

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