When talking about flame resistant fibers, they are designed to resist breakdown when exposed to flame or heat. This is important because most fibers will burn or melt (leading to dripping), causing a worse injury as it adheres to the skin and continues to burn (this is referred to as a secondary injury). When aramid fibers are exposed to fire, they will carbonize and self extinguish but will not drip or melt. Think of them as a sacrificial layer of protection. This makes them attractive for personal protective equipment (PPE), as well as a range of industrial applications.
There are a few different types of aramid fibers on the market. The two most commonly used in PPE is the meta-aramid and the para-aramid. These are manufactured around the world and sold under many trade names. In the United States, we know them most affectionately under their DuPont trade names: Nomex and Kevlar respectively. These are fibers structurally related to nylon, just with a slightly different chemistry. Aramids are made from aromatic rings with amide bonds holding them together. We then further delineate that into the meta and para configurations, with the meta-aramid having substitutes on the 1 and 3 positions on the aromatic ring and the para-aramid having substitutes on the 1 and 4 position on the ring. This produces significantly different fiber properties with the meta-aramid being more flexible but having a lower tensile strength and degradation temperature. Meta-aramids are generally designed to be soft on the skin and this has led to their widespread use in personal protective equipment. The AzoShield 211 FR glove utilizes meta-aramid fabric as its back of hand protection for this reason. Para-aramids have a much higher tensile strength than its meta-aramid cousin and therefore has other useful applications like ballistic protection. This is what is used in the palm of the AzoShield 211 FR glove to give it strength.
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