Nomex and Aramid

Nomex is a registered trademark for flame-resistant meta-aramid material developed in the early 1960s by DuPont and first marketed in 1967.

Properties

Nomex and related aramid polymers are related to nylon, but have aromatic backbones, and hence are more rigid and more durable. Nomex is the premier example of a metavariant of the aramids (Kevlar is a para aramid). Unlike Kevlar, Nomex cannot align during filament formation and has poorer strength. However, it has excellent thermal, chemical, and radiation resistance for a polymer material.

Production

The polymer is produced by condensation reaction from the monomers m-phenylenediamine and isophthaloyl chloride. It is sold in both fiber and sheet forms and is used as a fabric wherever resistance from heat and flame is required. Nomex sheet is actually a calendered paper and made in a similar fashion. Nomex Type 410 paper is the original and one of the larger grade types made, mostly for electrical insulation purposes. Nomex fiber is made in theUSA and in Spain(Asturias). Wilfred Sweeny (1926–2011), the DuPont scientist responsible for discoveries leading to Nomex, earned a DuPont Lavoisier Medal partly for this work in 2002.

Applications

The paper is used in electrical laminates such as circuit boards and transformer cores as well as fireproof honeycomb structures where it is saturated with a phenolic resin. Honeycomb structures such as these, as well as mylar-Nomex laminates are used extensively in aircraft construction. Both the firefighting and vehicle racing industries use Nomex to create clothing and equipment that can withstand intense heat. A Nomex hood is a common piece of racing and firefighting equipment. It is placed on the head on top of a firefighter’s face mask. The hood protects the portions of the head not covered by the helmet and face mask from the intense heat of the fire. Wildland firefighters wear Nomex shirts and trousers as part of their personal protective equipment during wildfire suppression activities. Race car drivers wear driving suits constructed of Nomex and or other fire retardant materials, along with Nomex gloves, long underwear, balaclavas, socks, helmet lining and shoes to protect them in the event of a fire. The FIA and the SFI Foundation provide specifications for flame-resistant drivers clothing to be used in racing. The standards range from single layer suits that provide some protection against flash fires to much thicker multilayer SFI-15 suits required by the National Hot Rod Association that can protect a driver for up to 40 seconds against the intense heat and almost invisible flames generated by the nitromethane, ethanol and methanol fuels that are used in championship drag racing. Military pilots and aircrew wear flight suits made of over 92 percent Nomex to protect them from the possibility of cockpit fires and other mishaps. Recently, troops riding in ground vehicles have also begun wearing Nomex. The remaining material is typically Kevlar thread used to hold the fabric together at the seams. Military tank drivers also typically use Nomex hoods as protection against fire and extreme cold. In the U.S. space program, Nomex has been used for the Thermal Micrometeoroid Garment on the Extravehicular Mobility Unit (in conjunction with Kevlar and Gore-Tex) andACES pressure suit, both for fire and extreme environment (water immersion to near vacuum) protection, and as thermal blankets on the payload bay doors, fuselage, and upper wing surfaces of the Space Shuttle Orbiter. It has also been used for the airbags for the Mars Pathfinder and Mars Exploration Rover missions, the Galileo atmospheric probe, the Cassini-Huygens Titan probe, as an external covering on the AERCam Sprint, and is planned to be incorporated into NASA’s upcoming Crew Exploration Vehicle. Nomex has also been used for its acoustic qualities, the first time being used in Troy, NY, at Rensselaer Polytechnic Institute’s Experimental Media and Performing Arts Center (EMPAC’s) main concert hall. A ceiling canopy of Nomex reflects high and mid frequency sound, providing reverberation, while letting lower frequency sound partially pass through the canopy. According to RPI President Shirley Ann Jackson, EMPAC is the first venue in the world to use Nomex for acoustic reasons. Nomex (like Kevlar) is also used in the production of loudspeaker drivers. Honeycomb-structured Nomex paper is also used as a spacer between layers of lead in the ATLAS Liquid Argon Calorimeter.

History

The death of race car drivers in fiery crashes, notably those of Fireball Roberts at Charlotte, and Eddie Sachs and Dave MacDonald at Indianapolis in 1964, led to the use of flame-resistant fabrics such as Nomex. In early 1966 Competition Press and Autoweek reported: “During the past season, experimental driving suits were worn by Walt Hansgen, Masten Gregory, Marvin Panch and Group 44’s Bob Tullius; these four representing a fairly good cross section in the sport. The goal was to get use-test information on the comfort and laundering characteristics of Nomex. The Chrysler-Plymouth team at the recent Motor Trend 500 at Riverside also wore these suits.”