Expanding when exposed to heat and saving lives, Nomex®is one of the best inherently Flame Retardant materials ever invented but how does it work?
Firstly, what does ‘inherently Flame Retardant’ mean?
This means that the actual structure of the fabric itself is non-flammable and can never be worn away or washed out. This, however, does not mean that the fabric doesn’t ignite.
A treated FR garment, however, is most often an organic fabric that is chemically treated to react and extinguish any flames.
Nomex®is a Synthetic Aromatic Polyamide Polymer.
This means that it is a manmade fibre, made up of connected rings of atoms & lots of molecules connected into chains to make one very strong fibre.
How is Nomex®made?
Nomex®is made up of four elements- carbon, oxygen, hydrogen & nitrogen.
Carbon-based substances react to form a liquid. This liquid is then spun out to make a solid fibre turning it into a sheet form.
The fibres misalign due to the honeycomb structure resulting in the Nomex®fabric having excellent thermal, chemical & radiation resistant properties protecting people using it.
Nomex® typically comes in 3 forms. It can come as:
-100% pure Nomex®
-Blended with up to 60% Kevlar
-or blended with a small amount of Kevlar and some anti-static fibres known as Nomex® III.
Nomex® is used in clothing for people such as firefighters, military personnel, race-car drivers & astronauts. And as it is such a great insulator, stopping heat & electricity passing through it is also used in things like oven-gloves and electrical equipment such as motors.
Where the magic happens…
The fabric is exposed to heat or flames and enlarges to hold the heat and protect the wearer.
How does this expansion work?
When Nomex® is exposed to heat the fabric carbonizes, absorbing all this warmth turning this into a protective barrier for the user.
Du Pont, the inventor of Nomex® says that the material performs in 3 distinct phases.
Phase 1- FLASHOVER- the garment may be exposed to up to 1000°c, the material swells and thickens, absorbing the heat and eliminating conductive heat transfer to the user. This then provides the worker with valuable seconds to escape the heat source.
Phase 2- ESCAPE- The Nomex® material will remain flexible and strong until it cools off.
Phase 3- RECOVERY- the worker removes the garments, the clothing will release the heat stored. Where the heat has been absorbed by the Nomex® material the fibres may solidify and crumble, but it has achieved its main aim which was to save that person’s life.
See what we can do to protect your life- Shop Flame Retardant Clothing
Thanks for reading and I hope you have learnt something about the physics of Nomex®and can see how it protects you in your daily life.