Textile for fire fighter clothing

Materials World magazine
1 Oct 2017

Dr Jennifer Unsworth of intellectual property firm Withers & Rogers describes high-performance textiles for firefighter clothing. 

Personal protective clothing for use by firefighters must meet specific, legislative performance requirements, including resistance to heat transfer by both flame and radiant heat. This month’s patent relates to a textile with improved thermal and wear properties, which has been developed by Yorkshire-based company, AW Hainsworth.

The company has been in the textile industry for over 200 years and was the provider of the first inherently heat- and flame-retardant material. It therefore specialises in the production of high-performance fabrics, which are compliant with current regulatory requirements. 

Textiles previously used for firefighter clothing included meta-aramid, polyamide-imide fibres or blends of both. Unfortunately, meta-aramid and polyamide-imide fibres have been found to shrink and thicken when exposed to high-temperature heat sources, which can have a negative impact on how the textiles wear while in use. 

In other instances, spun yarns or other staple mixtures are blended with para-aramid fibres. Using these specialist yarns to make fire-retardant or -resistant textiles helps them remain intact when exposed to heat. 

Recognising the importance of producing a textile that is both hard wearing and fire-resistant, AW Hainsworth has developed a new, improved textile that includes a woven fabric used on both its front and back faces. Woven fabrics include yarn or thread (known as weft), which is drawn through other yarns (known as warp), which are held in tension on a frame or loom. The woven face fabric of the patented textile incorporates multifilament yarns comprising a mixture of polybenzimidazole (PBI) and para-aramid fibres, as well as multifilament yarns of para-aramid and meta-aramid mixtures, within either the weft, or the weft and the warp. 

In contrast, the warp of the backing fabric is made from para-aramid yarns and the weft of the backing fabric includes a mixture of para-aramid and polybenzimidazole yarns.

Although PBI yarns have poor abrasion resistance, they have a number of beneficial properties when applied to firefighter clothing. In particular, they are flame resistant and help to resist melting and burning. They also offer low shrinkage when exposed to flames.

To take advantage of these beneficial properties, the R&D team at AW Hainsworth developed combinations of PBI, para-aramid and meta-aramid yarns to form textiles with strong fire resistance and physical wear properties. 

The figure of the patent shows a plan view of the innovative textile, made using a combination of fibres - Warp A and Weft A are para-aramid/PBI yarns, Warp B and Weft B are meta-aramid/para-aramid yarns, Warp C is 100% para-aramid yarn and Weft C is a para-aramid/polybenzimidazole yarn. 

This patent demonstrates how traditional know-how and an innovative approach to textile design and development of new materials can provide solutions for the most demanding of modern applications.        

 To view the patent, visit bit.ly/2weKy7m