Researchers at the University of Alberta, Canada, have solved the mystery of why a high-performance fabric commonly used in firefighting and other protective garments weakens prematurely when it’s exposed to moisture. They found that sulphur content in some high-performance fabrics weakens them when exposed to moisture.

“The breakthrough helps solve a big safety challenge. As the garment weakens over time, there’s no way to know whether the wearer is still protected or not. Now we know the root cause, and this gives information to the manufacturers to find a solution to this problem,” said Saiful Hoque, a PhD student in Textile and Apparel Science and researcher in the Faculty of Agricultural, Life, & Environmental Sciences.

The recent study investigated the accelerated hydrothermal aging of various fabrics typically used as outer shells in clothing for firefighters, oil and gas workers, and electricians, the University said in a press release.

The fabrics were immersed in water at temperatures ranging from 60° to 95° C for up to 1,200 hours. After exposure, some of them lost significant tensile strength — the stress a fabric can withstand without splitting or breaking — without showing any visible signs of degradation.

The cause was found to be the high sulphur content in some of the fibres, leading to an accelerated loss in fabric strength when exposed to moisture. That degradation weakens the safety of protective garments when exposed to sweat, water, rain, snow, or laundering.

Besides fibre damage, the water-repellent finish in some of the fabrics also showed degradation, which adds to safety concerns, Hoque notes. “When a fabric starts absorbing water it transfers more heat, which can result in burns. And water also makes what is already a heavy safety garment even heavier.”

The findings shed new light on what earlier University of Alberta’s research discovered about the sensitivity of some high-performance fabrics to water, said ALES professor Patricia Dolez. She led earlier research that showed laundering contributes to a loss in performance in some fire-protective fabrics.

Next steps are to share the latest findings with textile manufacturers, said Dolez, who was a co-author on Hoque’s study along with professor Hyun-Joong Chung and Ankit Saha of the University of Alberta’s Faculty of Engineering.

“We’re hoping to work with the industry to come up with solutions.”

The discovery will also strengthen ongoing research led by Dolez to develop end-of-life sensors that detect damage in firefighters’ garments.

“We now have the data we needed on the degradation of fire-protective fabrics (due to long-term exposure to water) to select the right material to use.”

The study was funded by the Natural Sciences and Engineering Research Council of Canada.