Flammability Requirements for Military Textiles
By Dr Nicola Davies
While the need for flame resistant (FR) fabrics for military textiles has always been prevalent, with the rise of the use of Improvised Explosive Devices (IEDs), the need for innovative and protective FR fabrics has become more urgent for militaries around the world.
But protection from fire is not the only challenge facing designers of military textiles. One of the other heat-related factors that may be impacted by FR design choices is the effect of the fabric on the wearer’s thermal signature, which refers to how targetable the wearer will be through near-infrared detection technologies. Some ways of advancing flame-resistance may simultaneously—positively or negatively—affect infrared detectability.
Heat and flame—as well as ballistics—protection are not the only considerations in designing and specifying military uniforms and fabrics. In an interview, researcher Aravin Periyasamy, of the Technical University of Liberec, emphasized, “Damage resistance, comfort, sweat management . . . and the integration of high-tech materials into uniforms” as some of the key parameters for all military textiles.
Current Status Quo in Military Textiles
Methods of flame-resistance fall into four broad categories:
- Strategic selection and configuration of natural fibers
- Chemical treatment of natural fibers
- Development of synthetics
- Strategic combinations and configurations of synthetics and natural fibers
Chemical treatment of natural fibers have been prone to failure due to laundering or exposure to chemicals in a soldier’s working environment. However, processes have been developed to overcome some of this fragility, and militaries do use some of these treated natural fibers, such as in FR treated cotton undergarments and T-shirts.
“Flame-resistance” in relation to textiles for military use doesn’t just mean that the fabric resists catching fire. Some popular synthetics such as nylon and polyester actually resist ignition and aren’t that easy to light on fire—but they tend to melt under intense heat, whether a flame is present or not. The severe localized burns that result from the hot, sticky melting substance produced can have grave consequences for a soldier in action.
The current state-of-the-art in FR military textiles includes:
- Cross-linked melamine polymers
- Other polymers
- Modacrylics specialty rayon fibers
- Chemically treated cotton and cotton blends
- Polybenzobisoxazole fibers
- Aramids (aromatic polyamides)
- Meta-aramids and FR viscose
- FR treated cotton
- Polybenzimidazole fibers
For military textiles, many countries may specify ISO (International Organization for Standardization), ASTM (American Society for Testing and Materials), or ANSI (American National Standards Institute) standards for FR testing of their fabrics. For example, ASTM D6413/D6413-13b, a vertical flame test for flame resistance of textiles, is cited in many military specifications.
One laboratory has reported that in a recent set of experiments, a 50/50 blend of wool and aramid outperformed many current FR textiles in terms of strength-to-weight ratio, durability, and comfort. The blend would also easily meet camouflage and anti-infrared-detection standards.
Some of the keys to these results were: (a) coaxing longer staple lengths out of the wool by using a long-staple worsted spinning system, and (b) removing the scales of the wool through the acid “superwash” process. Periyasamy envisions that going forward, “Better results will come from nano-technology-based flame resistance.”
With greater accessibility of sophisticated near-infrared detection and targeting—and the many openings for improvements in comfort, durability, and cost—there is a clear need for continued development of heat and flame resistance for military textiles.