This is our second post in the series, FRC: How It’s Made, our month-long series spotlighting the process to make an FR garment from the fiber and yarn weaving, engineering of FR, all the way to garment manufacturing with videos and commentary from industry experts.
Today we focus on the process used to engineer the fabric that delivers flame resistance to arc rated and flame resistant (AR/FR) clothing. The short video below, featuring Tyndale’s Vice President of Technical, Scott Margolin, covers the difference between inherent and treated fabrics, and how the flame resistance is engineered.
There are a number of processes for creating quality, durable FRC, but they can essentially be grouped into two, basic categories – inherent and treated. Both processes, when done properly, can create flame resistance that’s guaranteed for the life of the garment.
The truth is that ALL AR/FR garments in common use for secondary PPE in the USA today are engineered through chemistry. The main difference between inherent and treated is that the engineering of inherent FR is done on the fiber level, while the engineering of treated FR is done at the fabric level (but usually still inside the fibers).
If you’re familiar with the Fire Triangle, you know that there are three ways to extinguish a flame – remove the heat, the oxygen, or the fuel. Some inherent fibers char instead of burning, which removes the fuel, and some both char and actively extinguish using free radical oxygen scavengers, which, as the name implies, remove the oxygen. The continuous fiber is then chopped into short lengths, crimped, then it’s ready to be spun into yarn and woven into fabric.
Treated FR on the other hand, refers to a fabric that has been engineered with flame-resistant chemistry to include FR properties that were not present prior to the treatment. Treated products begin with a fabric and conduct the FR engineering within the existing fibers of that fabric.
Most treated fabrics are cotton-rich, and manufacturers are able to create an FR fiber inside the hollow core of the cotton fibers, where it won’t be washed or worn out. The various processes differ somewhat, but most involve THPC chemistry, which is applied as a liquid by running the fabric through a bath and enabling the solution to penetrate the core of the hollow fibers. Once the fabric is properly wet out, it runs through rollers that set the correct temperature and other important parameters, and is then transferred into a gaseous ammonia cure chamber. This chamber is where polymerization occurs. Polymerization of the garment cures the new FR fiber matrix inside the hollow cotton core. It’s like a two-part epoxy you’d get your local hardware store: there’s a part A and a part B, and once you mix them, they form a new substance (part C), then there is no going back to part A or B.
The fabric that emerges from the chamber is now flame resistant and ready to be scoured, rinsed, and finished. Like many of the inherent fabrics, these FR cotton fabrics char instead of burning…no fuel, no fire. Just like inherent fabrics, many treated flame resistant garments are FR for the life of the garment.
As you can see, both inherent and treated FR fabrics use complex chemical engineering processes to create their life-saving properties, and both result in durable, reliable fabrics. All FR clothing Tyndale sells is guaranteed flame resistant for the life of the garment and is easily washed at home without special handling.