Nomex is used in a wide range of applications due to the fabric capabilities and thermal properties when there is a possible exposure to a fire source or an electric arc flash. Following are some of the more common Industries and applications that Nomex garments are used in as protective garments
These applications include but are not limited to industrial work wear for:
- petroleum and petrochemical operations - electricians - utility workers - race car drivers and their crews
- the military - NASA astronauts and their crews - medical emergency professionals - any industry where there is a chance of flash fire exposure or electric arc flash or blast
Nomex Clothing
As you can see there are many uses for Nomex garments which are manufactured by various
companies into different styles and designs of clothing. Protective clothing is available in coveralls, bib overalls, work shirts, work pants and jackets. The coveralls, bib overalls and jackets are also available as insulated styles for temperatures from mildly cold to extreme cold.
The protection provided from Nomex garments gives a person the benefit of a few seconds escape time and the characteristic of Nomex to self extinguish once the person has been removed from the flame source. If the flame source is not removed within a few seconds the fiber will start to char which results in that area not providing any more fuel for the flame in that particular location.
The military have been utilizing Nomex garments for many years in the form of personal protection garments when going into combat situations. The assurance that the garment you are wearing will not become part of a fuel source for a flash fire can save a life in certain combat situations.
Nomex is usually used either alone or in a blend with Kevlar® for fire fighters turn out gear and station wear. Fire fighting crews also utilize a combination of Nomex and Kevlar which provide a thermal protection for contact with a flame source.
Moisture barriers which are incorporated into Nomex fire fighters turn out gear utilize a lightweight blend of Nomex and Kevlar to provide a thermal liner that results in helping to reduce heat stress.
Nomex suits are very popular in the sport of auto racing as personal protection in the case of accidents on the track or in the pit that may result in a flash fire incident. It is recommended that not only the vehicle driver have the protection of a Nomex garment but also any personal that may in any way become involved in an accidental fire situation.
The characteristics of Nomex fabric are what makes Nomex a very good choice for the design of flame resistant apparel. The fiber is composed of a synthetic chemical that is in it's self inherently flame resistant. This flame resistant property can not be washed or dry cleaned out of the Nomex fiber and is therefore good for the life of the garment.
Nomex will not burn in air like a cotton fabric and will not melt and drip like a polyester fabric. When exposed to a heat source the Nomex fabric will actually expand form the heat source resulting in establishing a defensive mechanism from the flame source.
When exposed to a flame source Nomex absorbs the heat energy and the fiber will swell up, thickening in the process which in turn helps to stop heat transfer to the individual person.
In the case of static electricity which can possibly be a hazard in petroleum plants Nomex IIIA incorporates a static dissipate which attracts static charges to it's carbon core which results in lowering the static charge. Kevlar is also added to the Nomex IIIA to help establish a stronger break open point for the garments. This addition of 5% Kevlar also helps establish Nomex IIIA as having a better abrasive resistant factor and longer garment life compared to FR Cotton fabrics.
The physical action of the Nomex fiber when exposed to a heat source such as a flash fire or electric arc is as follows:
• The fiber itself absorbs heat energy during the carbonization process.
• The fiber swells and thickens in size and seals openings in the garment fabric helping to eliminate air movement and heat transfer to the interior skin area.
As both the fiber and the fabric thicken together this increases the insulating barrier and therefore reducing heat transfer to the person.
Nomex IIIA has a static dissipative added to the fibers that helps control static electricity in certain applications where the presence of even a small electrical discharge could cause an ignition source. The static dissipate that is added to Nomex is P-140 which is a carbon core and insulating sheath. The properties of the P-140 attract static charges from the fabric until the buildup of static electricity ionizes the surrounding air molecules resulting in reducing the charge.
Nomex IIIA maintains it's static dissipation qualities even in low humidity conditions where 100% cotton fabric may not provide as much anti-static protection. This is due to the fact that 100% cotton relies on the absorption of moisture to help eliminate the static buildup. When subject to low humidity conditions cotton will not be able to provide the same protection as the Nomex IIIA due to the loss of moisture. As mentioned above Nomex IIIA has the ability to maintain it's anti static buildup even in low humidity conditions.
In the construction of flame resistant apparel Kevlar and Nomex are the fabrics of choice. Depending on the application the choice between the two fabrics is one of comfort and protection requirements. Kevlar is much more abrasive resistant then Nomex and is therefore used in a higher concentration percentage of garment fabric design in professional firefighter's turnout gear. Where as Nomex is a softer feeling fiber and is used to a higher degree in daily use garments because of it's greater comfort provided to the wearer. Kevlar is however added to Nomex IIIA to provide a higher degree of strength to the apparel.
In the the process of adding Kevlar to the Nomex material however there is a decrease in the thermal protection due to the characteristics of the two materials. What happens is that in order to provide a stronger material and a reduced break open point the result is that the material fibers will have a reduced flame shrinkage which in turn makes the fiber stronger but at the same time there is a loss of the barrier material and insulating air layer between the flame source and the wearer, potentially increasing burn injury. Because of this in the case where more protection is required, multiple layers of Nomex IIIA may be required to achieve the desired protection when exposed to electric arc incidents.