A pair of new University of Alberta studies show how to make firefighters' clothing safer to wear, maintain and manufacture.
One study revealed that some fibres used in the protective gear break down when exposed to warm water, showing what can happen to the garments over time, during real-life firefighting scenarios and laundering.
The other study analyzed the water used in the manufacture of fibres, identifying a handful of harmful dye compounds leaching from the fabrics that could weaken their protective qualities.
"The findings of both studies show vulnerabilities and potential ways to improve the materials currently being used in firefighters' clothing, and for maintenance," says Saiful Hoque, who conducted the work to earn a PhD in textile and apparel science from the Faculty of Agricultural, Life & Environmental Sciences (ALES).
Wear and care
Using accelerated aging treatments reflecting firefighting and laundering conditions, one of the studies investigated the effects of heat and water on 15 different yarns in eight fabrics typically used to manufacture protective clothing.
The fibres were immersed in both purified neutral pH and acidic water ranging from 40 C to 90 C for up to 1,200 hours at a time, then checked for physical, chemical and other types of deterioration. The results of the hydrothermal aging showed that fabric blends containing a particular type of fibre, called para-aramid/polybenzimidazole, or PBI, degraded in strength 68 per cent more quickly when exposed to moisture, as opposed to similar fire-protective fabrics that didn't contain PBI.
High-performance fibre blends containing PBI are typically used to make firefighters' outer jackets and trousers, due to the fibre's flexibility and ability to withstand extreme temperatures.
But because PBI fibres are manufactured using sulfuric acid, traces of the chemical remain behind, shows an earlier study led by Hoque. That residual sulphur increases a fabric's sensitivity to moisture, and could lead to premature degradation of protective garments, Hoque notes.
The findings can help manufacturers of high-performance fibres and protective fabrics improve their processes, he suggests.
"PBI fibres are still good to use, but it's critical that producers develop ways to remove the residual sulphur from those fibres."
Laundering of firefighting gear also needs to be changed up, by washing clothing with PBI fibres separately, Hoque advises. "This prevents the risk of damage to neighbouring fabrics that don't contain PBI fibres and wouldn't otherwise experience degradation in warm water."
The same study also established, for the first time, that meta-aramid fibres, another type commonly used in protective clothing, showed "remarkable resistance" to heat and water stress, even when exposed to acidic water, Hoque says. For example, one fabric sample comprising 93 per cent meta-aramid fibres lost only four per cent of its tensile strength after being immersed in water for 1,200 hours at 90 C.
That discovery fills a knowledge gap about the effectiveness of high-performance fibres to resist heat and water, allowing manufacturers "more informed decisions in the selection and design of materials for more durable gear for firefighters," Hoque says.
It also opens up possibilities for using meta-aramid fibres in other products frequently exposed to water, such as marine safety equipment, he adds.
The overall exploration of the various yarns and their fibres provides a fuller understanding of their durability, Hoque says. "We can now offer manufacturers suggestions for optimum fibre blends and fabric configurations that strike a better balance between long-term protection and comfort."
Responsible manufacture
Hoque's second study developed a method of analyzing the water used in the experiments, which can be used by fabric manufacturers to make their production processes more environmentally sustainable, he says.
The analysis identified three dye-related compounds known to pose some risk to the environment, "particularly when they leach into water systems," he notes.
Though not recommended for use, "it's possible that some manufacturers still employ these compounds, so this information can help them prevent environmental pollution and adopt more sustainable practices."
Hoque's various co-authors on the pair of studies were ALES associate professor Patricia Dolez, professor Hyun-Joong Chung and master's student Ankit Saha in the Faculty of Engineering, and professor James Harynuk, research associate Paulina de la Mata and PhD candidate Trevor Johnson in the Faculty of Science.
The two studies received funding from the Natural Sciences and Engineering Research Council of Canada, Mitacs, Davey Textile Solutions Inc. In-kind support was provided by Innotex and DuPont. The research was also supported by the U of A Protective Clothing and Equipment Research Facility, the U of A nanoFAB and the U of A Department of Chemistry.
