To mitigate the risk of fire accidents caused by flammable textiles and reduce the potential harm to life and property, the assessment of the burning performance of textile materials has garnered considerable attention worldwide. This article will discuss Textile Flame Retardancy Evaluation.

Judging the flame-retardant performance of fabrics generally relies on two aspects.

Firstly, the assessment is based on the fabric’s burning speed. This involves subjecting the fabric, treated with flame retardant as per specific procedures, to direct contact with flames for a defined duration, followed by the removal of the ignition source. The duration of continued flame and non-flame burning, along with the extent of fabric damage, is then measured. Shorter flame and non-flame burning periods, accompanied by less extensive damage, indicate superior flame-retardant properties. Conversely, longer durations and increased damage signify poor flame retardancy.

The second aspect involves evaluating the material’s limiting oxygen index (LOI). The LOI quantifies the amount of oxygen required for combustion. Consequently, the flame-retardant performance of the fabric can be determined by measuring this index. Higher LOI values indicate a greater oxygen concentration necessary to sustain combustion, thereby suggesting increased resistance to ignition. This index is represented as the minimum percentage of oxygen volume required to sustain candle-like combustion of the sample in a nitrogen-oxygen mixture. Theoretically, as long as the LOI of textile materials exceeds 21% (the volume concentration of oxygen in natural air), they possess self-extinguishing properties in the ambient atmosphere.

Based on the LOI values, textile products are typically classified into four categories: inflammable (LOI < 20%), combustible (LOI = 20% – 26%), difficult to ignite (LOI = 26% – 34%), and non-flammable (LOI > 35%). Their LOI characterizes the flammability of textiles. According to this parameter, textile materials are classified into four categories: non-flammable (LOI ≥ 35%), such as most metal fibers, carbon fibers, asbestos, boron fibers, glass fibers, PBO fibers, PBI (polybenzimidazole) fibers, and polyimide fibers; difficult to ignite (LOI = 26 – 34%), such as aramid, fluorine, chlorine, modified acrylic, modified polyester, modified polypropylene, modified viscose, PPS (polyphenylene sulfide), and seaweed fibers; combustible (LOI ≥ 26% ≤ 34%), such as polyester, nylon, vinylon, wool, silk, and acetate fibers; and easily ignitable (LOI ≤ 20%) materials, such as polypropylene, acrylic, cotton, flax, viscose fibers, bamboo pulp fibers, soy protein fibers, and milk protein fibers.

While non-flammable fibers exhibit strong flame-retardant properties, they are generally unsuitable for wearing or household use. Most commonly used natural or chemical fibers are flammable or easily ignitable. Enhancing their flame-retardant properties necessitates modification or post-processing treatment, wherein flame retardants are incorporated into textiles through various means. The path to achieving fiber flame retardancy involves preventing or reducing fiber thermal decomposition, isolating or diluting oxygen, and rapidly cooling to suppress combustion. In practice, this often involves the addition of flame retardants with specific functionalities into chemical fibers through processes such as polymerization, blending, copolymerization, composite spinning, and modified surface treatment. Our company can supply fire-retardant polyester chips, which are obtained through the copolymerization process. The LOI can be more than 35. For more details, you can refer to