Products Catalog

Specification

NOMEX® IIIA

FLAME AND STATIC RESISTANCE

NOMEX® IIIA
TECHNICAL BRIEF

The Need
Protective apparel of NOMEX® IIIA resists intense heat,
flame and break open, hazards associated with exposure
to electric arcs.
Protection against intense heat and flame
Du Pont NOMEX® IIIA does not melt and drip, burn or
support combustion. When exposed to flame, the NOMEX®
aramid fiber carbonizes and becomes thicker ( Figure 1) ,
forming a protective barrier between the heat source and
the skin. This protective barrier stays supple until it cools,
giving the wearer extra seconds of protection for escape.
The polymer from which the NOMEX® aramid fiber is spun
does not support combustion. The flame resistance is built
into the fiber itself; it does not come from a topical chemical
treatment. Therefore, the flame resistance of garments of
NOMEX® IIIA is permanent; no amount of laundering or
wear can remove it.
Protection against break open from the Arc
Blast - Garments of NOMEX® IIIA resist break open.
Incorporating high-strength Du Pont KEVLAR® aramid
fiber — the same fiber used in bullet-resistant vests —
garments of NOMEX® IIIA protect against the explosive
force of an electric arc. In fact, tests predict that garments
of NOMEX® IIIA will provide greater protection from break
open than comparable weight fabrics of flame-retardant
treated cotton.
Protection against fabric sparking - Because static
electricity can be a nuisance and a concern to electric utility
workers, NOMEX® IIIA also incorporates P-140, a proprietary,
Du Pont static-dissipative fiber. NOMEX® IIIA reduces static
generated from fabric-to-fabric and fabric-to-surface
rubbing. This makes garments of NOMEX® IIIA more
comfortable to wear by reducing nuisance static even at
low temperatures and in low humidities. It also reduces the
contribution of clothing to the static hazard in explosive environments.

The Fabric Properties
Thermal Protection - To demonstrate the extra margin
of safety provided by NOMEX® IIIA, various fabrics were
evaluated in thermal protective performance ( TPP) testing.
This test predicts the heat energy required to pass through
a fabric and cause a second-degree burn under laboratorycontrolled
heat conditions. The higher the TPP, the more
thermal protection the fabric provides. For single-layer
fabrics, this test also measures the ability of a fabric to
maintain a protective barrier between the fire and the wearer.
As you can see from the table below, both the cotton and
polyester/ cotton blend ignited, and therefore, no meaningful
TPP values could be obtained. In contrast, NOMEX® IIIA
provides excellent TPP values, significantly higher than even
the heavier weights of flame-retardant treated cotton
commonly used. For example, a light, 6 oz/ yd2 fabric of
NOMEX® IIIA has a TPP value of 13.1 cal/ cm2, while a 9.0
oz/ yd2 flame-retardant treated cotton has a TPP value of
only 9.8 cal/ cm2.
Thermal Protective Performance ( TPP) * of various fabrics* *
Fabric Nominal
Weight Ignites TPP
( oz/ yd2) ( YES/ NO) ( cal/ cm2 )
NOMEX® IIIA 4.5 NO 10.6
NOMEX® IIIA 6.0 NO 13.1
NOMEX® III
( Without staticdissipative
fiber) 6.0 NO 13.1
Cotton 6.5 YE S * * *
Polyester/ Cotton
Blend ( 65% / 35% ) 7.0 YE S * * *
Flame-Retardant
Treated Cotton 6.0 NO 7.6
Flame Retardant
Treated Cotton 9.0 NO 9.8
* Fabric was tested according to ASTM D-4108 recommended
mounting procedures to test single-layer fabrics, using combined
radiant and convective heat.
* * Each fabric was home laundered five times prior to testing.
* * * Fabric ignited and did not pass the flame resistance test ( vertical
flame test) , so meaningful TPP values could not be obtained.
NOMEX® IIIA
TECHNICAL BRIEF
NOMEX® IIIA

Anti-Static Performance
NOMEX® IIIA reduces the static generated from fabric-tofabric
and fabric-to-surface rubbing, thus:
• Reducing nuisance static, which can be unpleasant or
cause a concern to the wearer;
• Improving garment comfort and wearability;
• Providing an added margin of safety in explosive
atmospheres.
NOMEX® IIIA significantly reduces the contribution of
clothing to the static hazard in explosive atmospheres. It
does not, however, eliminate the need to ground the body
and equipment in such situations. The object of grounding
is to provide a safe path for static charges to reach the
earth.
Charge Decay Testing
The excellent anti-static performance of NOMEX® IIIA has
been demonstrated in fabric testing. Fabrics made of military
end uses pass the charge decay test ( Federal Test Method
Standard 101C, Method 4046) , which qualifies fabrics for
use in hospital operating rooms.
Fabrics of NOMEX® IIIA also pass a more stringent version
of this test. In this test, the fabric is placed between two
parallel electrodes, and must accept a charge of at least 3
kV when 5 kV are applied. The fabric must then discharge to
10% of the original accepted charge in less than one-half
second after grounding. Fabrics are tested at 70º F. and 20% relative humidity.

Triboelectric Rub Testing
In addition, NOMEX® IIIA performs exceptionally well in
triboelectric rub testing, even under low humidity conditions.
This test measures the intensity of the charge field on the
surface of a fabric after it has been rubbed by a paper towel
or other material.
Even after 150 launderings, fabrics of NOMEX® IIIA have
field intensities less than 7.5 kV/ in. According to published
references, 1, 2 fabrics with intensities less than 12 kV/ in. are
likely to prevent spark ignition in most hydrocarbon vapor/
air mixtures, * * assuming proper grounding procedures have
been followed.
Anti-Static Test Results ( 70º F / 20% RH)
CHARGE DECAY TRIBOTESTING
ELECTRIC
RUB TESTING
Seconds to
10% of Initial
# of Kilovolts Kilovolts
Fabric Launderings Accepted Accepted kV/ in.
NOMEX® IIIA 0 3.95 0.01 4.1
25 3.75 0.02 6.9
50 3.45 0.01 7.2
75 3.15 0.02 7.3
100 3.10 0.01 6.9
150 3.10 0.02 6.1
NOMEX® III 0 4.50 8.9 12.3
25 1.35 > 10 14.5
50 1.35 > 10 14.8
75 1.35 > 10 13.9
100 1.35 > 10 14.6
100% Flame- 0 3.25 > 10 18.6
Retardant 25 2.00 > 10 15.6
Treated Cotton 50 1.60 > 10 16.6
65% / 35% 0 4.90 4.3 9.6
Polyester/ 25 2.20 > 10 18.0
Cotton 50 2.25 > 10 17.8

NOMEX® fiber blends have good resistance to many
chemicals, such as organics, acids and bases. Specific
behavior when exposed to a particular chemical is described
in our Technical Information Bulletin NX-17. However, despite
the fact that the NOMEX® fiber itself has good chemical
resistance, most garments of NOMEX® IIIA are made of
woven fabrics, which are not designed to protect the wearer
against chemicals. Put on Product PartnerRecommend to your friends