U.S. patent application number 13/659738 was filed with the patent office on 2013-05-16 for flame, heat and electric arc protective yarn and fabric.
This patent application is currently assigned to INTERNATIONAL GLOBAL TRADING USA, INC.. The applicant listed for this patent is INTERNATIONAL GLOBAL TRADING USA, INC.. Invention is credited to Alceu Aragao, Hoyt M. Layson, JR..
Application Number | 20130118635 13/659738 |
Document ID | / |
Family ID | 48279481 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130118635 |
Kind Code |
A1 |
Layson, JR.; Hoyt M. ; et
al. |
May 16, 2013 |
Flame, Heat and Electric Arc Protective Yarn and Fabric
Abstract
A flame, heat and electric arc protective yarn that can be used
for knitting and weaving a single layer fabric. Both knitted and
woven fabrics are for use as a single layer flame, heat and
electric arc protective fabric garment or as an outer layer of a
flame, heat and electric arc protective multiple layer garment or
accessory for a wearer.
Inventors: |
Layson, JR.; Hoyt M.;
(Orlando, FL) ; Aragao; Alceu; (Miami,
FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERNATIONAL GLOBAL TRADING USA, INC.; |
Miami |
FL |
US |
|
|
Assignee: |
INTERNATIONAL GLOBAL TRADING USA,
INC.
Miami
FL
|
Family ID: |
48279481 |
Appl. No.: |
13/659738 |
Filed: |
October 24, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12708552 |
Feb 19, 2010 |
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13659738 |
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61286111 |
Dec 14, 2009 |
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61298061 |
Jan 25, 2010 |
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Current U.S.
Class: |
139/420R |
Current CPC
Class: |
D03D 15/0005 20130101;
D03D 13/008 20130101; D10B 2331/021 20130101; D03D 15/12 20130101;
D03D 1/0035 20130101; B32B 27/12 20130101; D02G 3/443 20130101;
D03D 1/0041 20130101; A62B 17/003 20130101; B32B 5/26 20130101 |
Class at
Publication: |
139/420.R |
International
Class: |
D03D 15/00 20060101
D03D015/00; D03D 15/12 20060101 D03D015/12 |
Claims
1. A heat, flame and electric arc protective single layer fabric
for use as a protective garment for a wearer, the fabric having
opposing faces and comprising: interwoven warp and weft yarn
wherein the warp and weft yarn comprises a blend of 8 to 33 wt-%
Meta-aramid, poly(meta-phenyleneisophthalamide) fibers, 65 to 90
wt-% Para-aramid, poly-(p-phenylenterephtalamid) fibers, and 2 wt-%
anti-static metal fibers wrapped in a carbon core polyamide sheath;
the weft yarn and the warp yarn being identical to each other and
comprising the opposing faces of the fabric, wherein the fabric
provides ablative thermal protection on both opposing faces of the
fabric.
2. The fabric according to claim 1, wherein the ratio between the
weft yarns and warp yarns is identical, such that the total wt-%
ratio between meta-aramid and para-aramid in the weft yarns is the
same as the wt-% ratio between meta-aramid and para-aramid in the
warp yarns.
3. The fabric according to claim 1, wherein the warp and weft yarns
comprise identical twisted yarns.
4. The fabric according to claim 1, wherein the warp and weft yarn
are comprised of two identical staple yarns, the staple yarns
having a linear mass from Nm 70/1 or 143 dtex to Nm 35/1 or 295
dtex.
5. The fabric according to claim 1, wherein the weft yarn and the
warp yarn comprise each up to 2 wt-% of antistatic fibers.
6. The fabric according to claim 1, wherein the staple yarns are
ring spun yarns.
7. The fabric according to claim 1, wherein the composite warp and
weft yarns are plied and twisted staple yarns.
8. The fabric according to claim 1, having a specific weight from
about 170 to 350 g/m2.
9. The fabric according to claim 1, having one composite weft yarn
identical to the warp yarn.
10. A flame-resistant single layer fabric formed from ring spun
staple yarns consisting of: 8 to 33 wt-%
poly-m-phenylenisophtalamid (meta-aramid) fiber, 65 to 90 wt-%
poly-p-phenylenterephtalamid (para-aramid) fiber, and 2 wt-%
anti-static stainless steel fiber wrapped in a carbon core
polyamide sheath with a twist from 480 to 950 turns per meter (TPM)
in the Z direction.
11. Process for providing a composite yarn having flame-resistance
comprising: providing composite yarn of at least staple yarn made
from para-aramid fiber, meta-aramid fiber and anti-static fiber;
feeding composite yarn into a knitting or weaving machine with no
prior or established order; knitting or weaving the fibrous
structure with no concern regarding the order that the composite
yarn is fed into the knitting or weaving machine.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and is a
continuation-in-part of application Ser. No. 12/708,552 filed on
Feb. 19, 2010, and entitled "Flame, Heat and Electric Arc
Protective Yarn and Fabric," which itself claims priority to
Application Ser. No. 61/298,061, filed on Jan. 25, 2010, and
Application Ser. No. 61/286,111, filed on Dec. 14, 2009, both of
which are entitled "Flame, Heat, and Electric Arc Protective Yarn
and Fabric." The contents of these related applications are fully
incorporated herein for all purposes.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a flame, heat and electric arc
protective yarn and the resulting knitted and woven fabrics for use
as single layer garment or as an outer layer of protective garments
and accessories.
[0004] 2. Description of Related Art
[0005] In many industries and professions there is a need for
garments, gloves, aprons, coveralls, boots and hoods that provide
an increase in flame, heat and electric arc protection. Examples
are firefighters, flight line personnel, military pilots, steel
mill workers, oil drilling field personnel, and refinery operators,
welders and electrical workers. Typically these environments are
not environmentally controlled so heavy protective clothing in the
ambient temperature of the working conditions induces heat stress,
fatigue and reduces productivity and reaction time of these
workers. For example, a garment that protects firefighters against
heat, flame and electric arc in fighting structural fires is also
known as "Turn Out Gear". Turn out gear is normally quite heavy
because the multi-layer thickness of the garment that provides the
heat, flame and electric arc protection. The bulk of the turnout
gear therefore limits movement and induces heat stress so that the
effectiveness of the firefighter decreases with fatigue caused by
restricted freedom of movement and is the number one cause of
firefighter fatalities Turn out gear has both requirements for body
heat loss as well as flame and thermal protection, therefore heavy
weight outer shell fabrics can prohibit body heat loss and the
increased weight contributes to inhibiting body movement and heat
stress.
[0006] Fabrics from which flame, heat and electric arc protective
garments are constructed are required to pass a variety of
overlapping US and international safety and/or performance
standards, including NFPA 1971, NFPA 2112, NFPA 70E and MIL C
43829C. More stringent requirements for fabrics, such as airline
blankets where the presence of fuel increases the heat of a fire
can be found in FAA FAR 25.853.
[0007] Since flame, heat and electric arc protective garments are
in harsh work environments they are subjected to more severe
abrasion, rips and cuts than casual wear clothing. Any holes, rips
or cuts in these protective garments compromises their
effectiveness for the wearer and exposes undergarments and skin to
heat, flame and electric arc hazards.
[0008] Currently the most flame, heat and electric arc resistant
fibers are those which have already been chemically reduced and
furnace oxidized. These fibers belong to a family known as PAN
carbon fibers. PAN carbon fiber belongs to a family of acrylic
precursors, which were developed by companies that were established
commercial producers of textile grade acrylic fibers. Having a
carbon content of up to 68%, PAN carbon fibers have excellent
resistance to flame, heat and electric arc, but have extremely low
resistance to abrasion, rips and cuts, thereby preventing effective
application of 100% PAN carbon fibers to garments for harsh work
environments. Even laundering in washing machines will cause
breaks, rips and tears in PAN carbon fiber fabrics garments made
from PAN carbon fibers because the fibers are so brittle due to the
high carbon content.
[0009] Protective garments have also been made from natural
cellulosic fibers, such as cotton. Natural cellulose fibers are
inexpensive and fabrics made from such fibers are lightweight,
flexible and comfortable to wear. However, cotton fibers are not
durable and have poor abrasion, rip and cut properties. Although
comfortable, cotton fibers are not inherently flame resistant and
thus apt to burn. In order to provide flame, heat and electric arc
protection, cotton fibers (or the yarns or fabrics made with such
fibers) have historically been treated with a fire resistant (FR)
compound to provide such fibers (or the yarns or fabrics made with
such fibers) flame, heat and electric arc protective properties.
Treatment of cotton fibers (or the yarns or fabrics made with such
fibers) with an FR compound significantly increases the cost of
such fibers (or the yarns or fabrics made with such fibers). The FR
treatment is water soluble, therefore after 20+ launderings the FR
properties are lost and the fabric no longer provides the
protection as when the fabric was newly treated.
[0010] To mitigate the detrimental laundering effects on FR treated
fabrics and to avoid the cost associated with FR fabric treatment,
cotton fibers have been combined with modacrylic fibers that have
inherent flame resistant properties. The modacrylic fibers control
and counteract the flammability of the cotton fibers to prevent the
cotton fibers from burning. Although modacrylic fibers have
inherent FR properties, they also have low resistance to abrasion,
rips and cuts similar to cotton, so these fabrics comprised of
blends of these fibers have poor abrasion, rip and cut properties.
In addition the yarns resulting from the blending of natural cotton
fibers and modacrylic fibers are left unstable after thermal (flame
or heat) exposure, so these fabrics will not pass the additional
safety and performance certifications of thermal exposure cycling
for protective garments.
[0011] In an attempt to address the stability of fabrics after
thermal exposure, other inherently FR fibers, such as the aramid
family of fibers, have been added to fiber blends for yarns to
impart thermal stability to the fabric blend to ensure compliance
of the resulting fabric with the requisite safety and performance
standards by decreasing charring dimensions, melting and fabric
distortion and shrinkage in vertical flame tests of such fabrics.
Because of the presence of natural and cotton fibers, the blended
fabrics incorporating aramid fibers still lacked required
properties for abrasion, rips and cuts.
[0012] Pure aramid fabrics, especially para-aramid fabrics, provide
superior flame protection and durability, but are extremely rigid
and restrict body movement where meta-aramid fabics are more
flexible for flexibility and comfort, but do not provide superior
flame protection and durability.
[0013] Current state of the art can only provide a blend of 62.5%
para-aramid for better flame protection blended with a minimum of
40% meta-aramid for better comfort and flexibility.
[0014] Therefore, a need exists for fibers, yarns and fabrics that
incorporate fibers that are more wear resistant than natural
cellulosic fibers such as cotton for abrasion, rips and cuts,
provide the flexibility, durability and comfort advantages of
natural fibers and protection from flame, heat and electric
arcs.
[0015] 3. Related Art
[0016] US Patent 2006/0035553 A1 (hereinafter referred to as the
553 Publication) describes "at least two separate single plies each
having a warp and a weft system, the at least two separate single
plies being assembled together at predefined positions so as to
build "pockets." Although the 553 Publication describes para-aramid
fibers and para-aramid fibers amongst a plurality of other fibers,
there is no teaching or suggestion of a weight percentage within
the range of 65 to 90% by weight para-aramid as presently
claimed.
[0017] International PCT Publication WO 2004/023909 A2 (hereinafter
referred to as the 909 Publication) describes the formation of
"pockets . . . comprising at least two separate single plies each
having a warp and weft system, the at least two separate plies
being assembled together at predefined positions so as to build
pockets." The 909 Publication also describes two different yarns,
each with different shrinkage properties. Although the 909
publication mentions meta-aramid and para-aramid among the choice
of many fibers that can be used, nowhere is there a teaching or
suggestion of the mixture percentage by weight of meta-aramid,
para-aramid and anti-static fibers as presently claimed.
[0018] International PCT Publication WO 2005/099426 A1 (hereinafter
referred to as the 426 Publication) also describes a totally
different percentage by weight mixture of meta-aramid and
para-aramid than what is presently claimed. The 909 discloses 60 to
90 wt-% poly-m-phenylenisophtalamid (meta-aramid) and 10 to 40 wt-%
poly-p-phenylenisophtalamid (para-aramid), the first of at least
two weft systems comprising a blend of 85 to 95 wt-% meta-aramid
and 5 to 15 wt-% para-aramid. This does not teach or suggest the
claimed range of 65 to 90 wt-% para-aramid, 8 to 33 wt-%
meta-aramid and 2 wt-% anti-static. In addition the 909 Publication
describes two different weight percentages of the two ply weft
systems, on facing the wearer of the fabric again which is not the
embodiment of this invention.
[0019] U.S. Pat. No. 7,618,707 (hereinafter referred to as the 707
Patent) describes a protective fabric blend of PSA (polysulfoamide)
in EXAMPLE 1 at 55 wt-% with para-aramid at 45 wt-%. This does not
teach or suggest the materials and ranges claimed by the present
invention.
[0020] US Patent Application US 2003/0232560 A1 (hereinafter
referred to as the 560 Patent Application) describes a flame
resistant fabric made from a plurality of flame resistant yarns
including, but not limited to, meta-aramid and para-aramid yarns
and a plurality of tough yarns woven into the fabric. This does not
teach or suggest the materials and ranges claimed by the present
invention.
[0021] US Patent Application US 2009/0137176 A1 (hereinafter
referred to as the 176 Publication) describes a two layer fabric
which is stacked and sutured. The publication also discloses a
plurality of fibers including, but not limited to meta-aramid which
is not the embodiment of this invention. However, the '176
Publication does not teach or suggest the materials and ranges
claimed by the present invention.
[0022] US Patent Application US 2009/0258180 A1 (hereinafter
referred to as the 180 Publication) describes at least a two layer
fabric, the heat resistant fabric layer made from a plurality of
heat resistant fibers including, but not limited to meta-aramid and
para-aramid with no specification of wt-% of either fiber. This
does not teach or suggest the materials and ranges claimed by the
present invention.
[0023] All identified prior art does not disclose a percentage by
weight of para-aramid fibers above 62.5% for a single ply fabric,
the reason is that the fabric would be too stiff and uncomfortable.
The mechanical structure of the yarn disclosed in this invention
provides both superior flame and thermal protection while
simultaneously providing comfort, durability and flexibility
heretofore not achievable in a fabric using a percentag by weight
of para-aramid higher than 62.5% blended with meta-aramid.
SUMMARY OF THE INVENTION
[0024] This invention discloses several areas of unique techniques
and methods that start with fundamental understanding the
properties of fibers, the optimal mechanical construction of fiber
blends into staple yarns and composite yarns, and the most cost
effective simple weaving patterns of yarns into woven into single
and dual ply monolayer fabrics as well as these yarns into knitted
fabrics to yield the desired properties of protection from flame,
heat and electric arcs while achieving the additional properties of
wear ability, lightweight monolayer fabric, flexibility and comfort
with superior resistance to abrasion, rips and cuts. The properties
of these yarns when woven in a simple pattern on conventional
textile weaving machinery yield a durable monolayer fabric that
will endure rigorous work environments and launderings without
losing any desired and required flame, thermal and durability
protection properties. This innovative monolayer design offers
levels of flame, heat and electric arc protection formerly only
available in multilayer fabrics of heavier weight and greater
thickness. Additionally the simple construction of the yarn
provides enhanced protection from flame, heat and electric arcs
when knitted into garment accessories that require more
flexibility, tactile feel and dexterity such as gloves and
hoods.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a diagram illustrating the combustion mechanism of
fibers.
[0026] FIG. 2 is a diagram illustrating the face side of a woven
fabric warp and weft pattern.
[0027] FIG. 3 is a diagram illustrating the back side of a woven
fabric.
[0028] FIG. 4 illustrates the Z direction of staple yarn (Y1)
twist.
[0029] FIG. 5 illustrates the direction of composite yarn (TY1)
twist.
[0030] FIG. 6 is a table of the Thermal Transition Temperatures of
Fibers.
[0031] FIG. 7 is a table of NEMA insulation rations.
[0032] Similar reference characters refer to similar parts
throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0033] Due to its unique structure of the yarn, the resulting
fabric, knitted or woven, according to the present invention,
surprisingly can have a range of specific fabric weight, which is
lower than that of conventional flame, heat and electric arc
protective fabrics having comparable durability and thermal
properties when used as single layer fabric, knitted or woven, or
as an outer layer fabric of a layered protective garment. The yarn
of the present invention is designed to benefit not only woven
fabrics but also knitted fabrics as well.
[0034] In addition this invention provides flexibility and comfort
not available in fabrics using a % by weight of para-aramid above
62.5% blended with meta-aramid.
[0035] Thermal risks in fire situations against which human skin
has to be protected may be due to: [0036] Flames (convective heat)
[0037] Contact from hot solid objects (conduction heat). [0038]
High radiant temperature from localized source or from all around
(Radiant heat). [0039] Sparks, drops of molten metal, hot gases and
vapors. [0040] Electric arcs
[0041] Human tissue is very sensitive to temperature. When human
tissue is exposed to any of the above hazards, the body experiences
pain, second-degree and possibly third degree burns. Total heat
energy as low as 0.64 cal/cm.sup.2 (26.8 kJ/m.sup.2), results in a
sensation of pain, and 1.2 cal/cm.sup.2 (50.2 kJ/m.sup.2) causes
second-degree burns on exposed tissues. At 45.degree. C., the
sensation of pain is experienced, and at 72.degree. C. the skin is
completely burnt. The mode of transfer establishes the means by
which protection should be achieved. The rate of heat transfer is
measured in terms of heat flux, which is the quantity of heat
passing through unit area per second; it is expressed in
kW/m.sup.2. The measured heat flux determines the level of
protection required. In order to achieve thermal protection the
protective fabric/clothing should meet the following requirements.
[0042] Flame-resistance i.e. not change chemically or physically
[0043] Integrity i.e. not char, break, distort or melt [0044]
Insulation i.e. not directly transmit heat [0045] Liquid-repellency
i.e. not trap water which will turn to steam when heated
[0046] Heat's effect on a fiber can produce a physical (i.e.
melting, charring, breaking) as well as a chemical change such as
out gassing where the out gas component may lead to or accelerate
combustion. In order to understand the protective function of the
fabric and the garment, it is essential to understand the
combustion mechanism of the fiber. FIG. 1 describes the combustion
mechanism of fibers.
[0047] Fiber, yarn and fabric combustion is a complex phenomenon
that involves heating, decomposition leading to gasification,
ignition, and flame propagation. The rate of the initial rises in
temperature of the fiber depends on the fiber specific heat,
thermal conductivity, latent heat of fusion, vaporization or other
enthalpy changes that occur during the combustion. In thermoplastic
fibers, the physical changes are at second-order transition and
subsequently melting occurs at a melting temperature, whereas
chemical changes take place at temperature where thermal
degradation (pyrolysis) occurs and the temperature where subsequent
oxidation and combustion may occur. The different thermal
properties of different fibers are listed in FIG. 6. Fibers undergo
combustion when exposed to heat either directly or via the route of
pyrolysis (Tp)-oxidation-combustion (Tc) as indicated in FIG.
1.
[0048] Conventional ways to change the combustion of fibers: [0049]
Treating the material with heat-absorbing products [0050]
Increasing the pyrolysis temperature makes the material
heat-resistant i.e. inherently FR [0051] Preventing evaporation,
that is, to form non-volatile compounds in situ, called char [0052]
Eliminating the oxygen from the combustion zone preventing
combustion
[0053] This invention proposes that selecting fibers with the most
desired properties, then mechanically combining fibers into yarns,
then mechanically combining yarns can yield enhanced desired
properties beyond the desired properties of the fibers alone.
Weaving and knitting patterns can also produce further enhancement
of desired properties.
[0054] The flame resistance and retarding properties of the final
textile material depends fundamentally on the nature of the fiber,
then how fibers are arranged into yarns and the structure of the
fabric. The nature of the fiber dictates its inherent tendency and
ease of burning whereas the mechanical construction of fibers into
yarns and then yarns into fabric composition shows different types
of such constituents and gives an indication of the overall burning
behavior. The structure of yarn and fabric decides the rate of
burning and fabric construction, with the fabric weight, durability
and flexibility playing an important an important role in typically
deciding the suitability for different work wear applications.
[0055] The typical fabrics for work environments are listed below:.
[0056] For a hot environment in which the fire hazard is
principally a direct flame, a lightweight tightly woven
construction such as 150-200 g/m.sup.2 flame retardant (FR) cotton
sateen, would normally be used. [0057] A flame-retardant cotton of
about 250-320 g/m.sup.2 is recommended for a workshop in which the
garment is subjected to a continuous shower of sparks and hot
fragments as well as a risk of direct flame, a heavier fabric is
required and a raised twill or velveteen of about 320-400 g/m.sup.2
in FR cotton would normally be chosen. [0058] Moreover, with molten
metal splashes, the protection of the wearer against the heat flux
resulting from the impact is also important. In such cases, fabric
masses up to 900 g/m.sup.2 are normally found useful.
[0059] Note that for existing FR fabrics, the weight of the fabric
increases as the risk of 2.sup.nd and 3.sup.rd degree burns
increases which adversely impacts user comfort, articulation,
fatigue and mobility.
[0060] In the case of fire fighting, the immediate reflex action is
to control an emergency as quickly as possible and at the same time
take steps to minimize eventual damage to and loss of materials and
injury to persons. The objectives of a fire fighter reaching an
incident are to: [0061] Save life and to prevent/ minimize injury
[0062] Prevent / minimize damage to property [0063] Prevent or
minimize damage to the environment
[0064] The role of the fire fighters' personal protective clothing
is not only to protect the fire fighter but also to enable the fire
fighter to achieve above mentioned objectives. The type of
protective garments and the protection the garment offers are
selected on the basis on the degree of risk involved; fire-fighting
protective garments are classified as: [0065] Protective garments
for structural fire fighting or "Turn Out Gear" [0066] Fire Entry
suits or Bunker Suits
[0067] Typically these suits are multi-layered: [0068] Outer
Shell--Usually a blend of Nomex, Kevlar and PBI. The outer shell is
the first line of defense for flame, heat and electric arc
protection and protects the inside layers from damage and this
layer is the scope of this invention. [0069] Moisture
Barrier--Usually Gortex or Neoprene on cotton/polyester to prevent
water transfer to the firefighter's skin. [0070] Thermal
Barrier--Usually a quilted material comprising a batt of aramid
fibers.
[0071] Ergonomics is the important aspect that needs to be
considered, especially in performance garments such as firefighter
garments. On an emergency action field, lots of body movement takes
place, which puts lots of stress on the body if the garment is
heavy and restricts movement. When the outer shell provides better
flame, heat and electric arc protection, the other layers can be
reduced in thickness and weight generating less stress on the
firefighter.
[0072] Understanding the fundamental properties of a plurality of
fibers and then uniquely arranging the fibers mechanically offers a
composite yarn with the desired properties of the plurality of
fibers which then allows fabrics, woven and knitted, to leverage
those desired properties. The additional mechanical properties of
the weaving and knitting process, i.e. different patterns of weaves
and knits, can further enhance the desired properties to yield a
fabric optimized for the following properties: [0073] Protection
from flame and heat [0074] Protection from electric arc [0075]
Durability properties: [0076] Abrasion resistance [0077] Rip
resistance [0078] Cut resistance [0079] Laundering resistance
[0080] Lighter weight [0081] Better comfort [0082] Easier body
movement and articulation
[0083] The yarn of the present invention is comprised of
meta-aramid, para-aramid and anti-static fibers. The unique method
and technique of mechanically combining these fibers in certain
weight percentage ranges disclosed herein produces a yarn that
provides the unique combination of desired and enhanced desired
properties described above. Further mechanical weaving of this yarn
disclosed herein enhances these desired properties further.
[0084] Meta-aramid, poly(meta-phenyleneisophthalamide), is an
aromatic polyamide fiber. The processes for manufacturing
meta-aramid fibers have been Patented and Trademarked under the
names Nomex, Teijinconex, Kermel, X-Fiper and New Star. Regardless
of the process, the meta-aramid family of fibers possess excellent
physical and mechanical properties and can be dope dyed offering a
wide color range. Meta-aramid fiber, especially the copolyamide
type, offers outstanding heat resistance, being resistant to
melting even after many hours of exposure to heat. This thermal
durability prevents the fiber from breaking down after initial and
continued thermal exposure. 75% of original strength is retained
after exposure to dry-heat of 200.degree. C. for 1000 hours. 60% of
original strength is retained after exposure to wet-heat at
120.degree. C. for 1000 hours. The Limiting Oxygen Index (LOI) for
Meta-aramid fiber is over 28%. It is a flame retardant fiber that
will not burn, melt or drip. Above 370.degree. C. meta-aramid fiber
will start to carbonize and decompose. Meta-aramid fiber has
excellent heat insulating properties to reduce the amount of
transmitted heat through the fabric. These properties and its high
dielectric strength enable NEMA (National Electrical Manufacturers
Association) Class-H (Up to 180.degree. C.) insulative property
yarns to be produced. This property is key for protecting the skin
against 2.sup.nd and 3.sup.rd degree burns. FIG. 7 provides the
NEMA insulation ratings. Meta-aramid fiber's low stiffness and high
elongation give excellent textile-like properties and
characteristics for comfort, allowing processing on all types of
conventional textile equipment for making woven and knitted
fabrics. Meta-aramid fiber shows good resistance to .alpha.,.beta.
and ultraviolet radiation. For example, when meta-aramid fiber is
exposed at 1000 Mrad of .beta. radiation accumulation, it shows no
loss of strength. This extremely beneficial for outdoor work
environments where ultraviolet sunlight radiation breaks down
garment fibers making them brittle and reducing the level of flame,
heat and electric arc protections due to openings in the fabric
created by abrasion, rips and cuts. Certain work environments, such
as welding, generate large amounts of ultraviolet radiation where
welding occupation requires flame, heat and electric arc
protection. Although meeting many of the desired requirements for
flame, heat and electric arc protective apparel, at 370.degree. C.
meta-aramid fibers will carbonize, become brittle, break and will
become weaker to abrasion, rips and cuts.
[0085] Para-aramid, poly-(p-phenylenterephtalamid), is also an
aromatic polyamide fiber. The processes for manufacturing
meta-aramid fibers have been Patented and Trademarked under the
names Kevlar, Technora, and Twaron. Aramids belong to the fiber
family of nylons. Common nylons, such as nylon 6,6, do not have
very good structural properties, so the para-aramid distinction is
important. The aramid ring gives Kevlar thermal stability, while
the para structure gives it high strength. Para-aramid fibers
however are very difficult to dye.
[0086] The tensile modulus and strength of para-aramid is roughly
comparable to glass, yet its mass is almost half that of glass.
Para-aramid can be substituted for glass where lighter weight is
desired. Para-aramid has other advantages besides weight and
strength. Para-aramid has a slightly negative axial coefficient of
thermal expansion, which means para-aramid composites can be made
thermally stable. Para-aramid is very resistant to impact and
abrasion damage making it useful as a protective layer such a
ballistic protection vests. The higher the percentage of
para-aramid fibers in fabric yarns results in increased stiffness
and rigidity of the fabric. Therefore para-aramids are mixed with
other fibers in fabrics to provide damage resistance, increased
strain resistance, and to prevent catastrophic thermal failure
modes. The other fibers provide flexibility and comfort in the
resulting fabric. Para-aramid has a thermal conductivity of 0.30
BTU-in/hr.sup.2 per .degree. F. as opposed to meta-aramid at 0.26
BTU-in/hr.sup.2 per .degree. F. Para-aramid fibers are also very
difficult to cut.
[0087] Para-aramids have a few disadvantages for flame, heat and
electric arc protective clothing. Para-aramid fibers absorb
moisture, so para-aramids are more sensitive to moisture in the
environment, especially during laundering. Although para-aramid
tensile strength is high, its compressive properties are relatively
poor. Para-aramid fibers are also more rigid than meta-aramid
fibers. A weight % greater than 62.5% para-aramid blended with
Meta-aramid results in a rigid fabric that limits body movement and
articulation resulting in increased heat stress for the wearer of
the garment made with such a fabric.
[0088] The yarn fabric of the present invention has particularly
good mechanical properties due to the unique mechanical structure
of the yarn. Generally speaking, the larger the amount of
para-aramid fibers, the better the physical performance and
resistance of the fabric itself to break open during thermal
exposure. Preferably, the para-aramid fibers constitute from 65 to
90 wt-% of the overall weight of the fabric. The meta-aramid fibers
constitute from 33 to 8 wt-% of the overall weight of the fabric
with the remaining 2 wt-% being antistatic yarn.
[0089] Because of the ideal properties of the yarn, a single yarn
can be used to produce both knitted and woven fabrics without the
need for complex ordering of multiple yarns or complex knitting or
weaving patterns, each with different properties to achieve desired
properties or differences in the level of protection. Since a
common yarn is used there is also no difference in properties
related to the face or back side of the fabric.
[0090] Therefore, according to a preferred embodiment of the
present invention, advantageously the warp and weft systems of the
woven fabric and the yarn for knitted fabric are based on the same
twisted yarn making the properties of para-aramid and meta-aramid
available to all exposed surfaces of knitted and woven fabrics.
Furthermore, the fabric according to the present invention can be
manufactured under standard process conditions by using
conventional machines for weaving or knitting single ply and double
ply single layer structures, thus rendering its production easier
and more cost efficient. Single layer fabrics offer increased
comfort and induce less stress on the wearer during periods of
physical activity.
[0091] The staple yarn (Y1) is a ring spun staple yarn consisting
of: 8 to 33 wt-% poly-m-phenylenisophtalamid (meta-aramid) fiber,
65 to 90 wt-% poly-p-phenylenterephtalamid (para-aramid) fiber, and
2 wt-% anti-static stainless steel fiber wrapped in a carbon core
polyamide sheath with a twist from 480 to 950 turns per meter (TPM)
in the Z direction. FIG. 4 depicts the Z direction of the ring spun
yarn.
[0092] A flame-resistant spun composite yarn (TY1) consisting of:
two staple yarns plied and twisted together, the resulting
composite yarn having a linear density of Nm 55/2 or 370 dtex of
650 twists per meter (TPM) in the S direction. FIG. 5 depicts the S
direction of the plied and twisted TY1 yarn.
[0093] Another preferred embodiment of the present invention, the
number of fibers constituting the weft systems have 22 TY1 yarns
and the fibers constituting the two warp systems have 38 TY1 yarns.
Such difference in the yarn count of the fibers constituting the
warp and weft systems is mainly due to the fact that the finer the
weft weave the better thermal insulation they provide so that lower
yarn count will be advantageously used for the two weft systems,
which weft system predominantly appears on both the fabric sides
facing away from and towards the wearer.
[0094] Accordingly, in order to further increase the insulation
effect of the fabric, particularly for exposures to heat and flames
in excess of three (3) seconds, the linear mass values of the
fibers constituting the weft systems will be identical to those of
the fibers constituting the warp system. Advantageously t here is
no difference on the side of the fabric facing away from or towards
the wearer. FIG. 1 depicts the warp/weft weave pattern for the face
of the fabric. FIG. 2 depicts the warp/weft weave pattern for the
back side of the fabric.
[0095] Advantageously, the TY1 yarn for the one and two weft
systems and the one and two warp systems of the woven fabric or the
knitted fabric according to the present invention comprise each up
to 2 wt-% of antistatic fibers. The presence of such fibers enables
to prevent, to dissipate or at least to strongly reduce electrical
charges that may be produced on the surface of the fabric.
[0096] A second aspect of the present invention is a garment for
protection against heat, flames and electric arc comprising a
structure made of at least one layer of the fabric described
above.
[0097] A third aspect of the present invention is a garment that
comprises a layered structure comprising an internal layer, a
middle layer made of a breathing waterproof material, and an outer
layer made of the above-described fabric of the invention.
[0098] The internal layer can be an insulating lining made for
example of a layer of two, three or more plies. The purpose of such
lining is to have an additional insulating layer further protecting
the wearer from the heat.
[0099] The internal layer can be made of a woven, a knitted, a
non-woven fabric and composites thereof. Preferably, the internal
layer is made of a fabric comprising non melt able fire resistant
materials, such as a woven fabric quilted with a fleece both made
of the para-aramid and meta-aramid blend described in this
invention.
[0100] The garment according to the present invention can be
manufactured in any possible way. It can include an additional,
most internal layer made, for example, of cotton or other
materials. The most internal layer is directly in contact with the
wearer's skin or the wearer's underwear.
[0101] The garment according to the present invention can be of any
kind including, but not limited to jackets, coats, trousers,
gloves, hoods, aprons, overalls, blankets and wraps.
[0102] The invention will be further described in the following
Examples.
EXAMPLE 1
Invention
[0103] A blend of fibers, commercially available, one under the
trade name Twaron poly-paraphenylene terephthalamide (para-aramid)
1.7 dtex having a cut length of TBD from AKZO, and another fiber
poly-metaphenylene isophthalamide (meta-aramid) 2.2 dtex having a
cut length of TBD from TBD and 2 wt-% of carbon core polyamide
sheath stainless steel fibers was ring spun into a single staple
yarn (Y1) using conventional staple yarn processing equipment.
[0104] The meta-aramid fibers had a cut length of 51 mm and a
linear density of 1.7 dtex. The para-aramid fibers had a cut length
of 50 mm and a linear density of 2.2 dtex. The anti-static fibers
had a stainless steel fiber with a cut length of 40 mm and a linear
density of 6.8 .mu.m.
[0105] Y1 had a linear mass of Nm 55/1 or 185 dtex and a twist of
700 Turns Per Meter (TPM) in Z direction. FIG. 4 depicts the spin
direction Z for staple yarn Y1.
[0106] Two Y1 yarns were then plied and twisted together. T he
resulting plied yarn (TY1) had a linear density of Nm 55/2 or 370
dtex and a twist of 650 TPM in S direction. FIG. 5 depicts the spin
direction S for composite yarn TY1.
[0107] TY1 was used as both the waft and warp yarn for woven
fabric.
[0108] A fabric weave having a special weave plan as described in
FIG. 2 and FIG. 3 was prepared. This fabric had 38 yarns/cm (warp)
of TY1 (19 yarns/cm per ply), 22 yarns/cm (weft) of TY1 (11
yarns/cm per ply) and a specific weight of 230 g/m.sup.2 according
to the 2/1 right twill construction. The woven fabric was tested
for shrinkage after 5 launderings using ISO 6330:2000. The warp
shrank 1% and the weft shrank 1.2%.
[0109] The following physical tests were carried out on the fabric
described in this Example 1: Determination of the breaking strength
of the warp was 1619 N and the weft was 1141 N and was conducted
using ISO 13934-1:1999 test procedure. Determination of the tear
resistance of the warp was 67.87 N and the weft was 34.4 N and was
conducted using ISO 13937-1:2000 test procedure.
[0110] Samples were sent to a US Government certified testing lab
for the following test results which in every case exceeded the
certification requirements:
Report 1 Certified Test Report for NPPA 70E 2009 (Vertical Flame
Test) from an independent testing lab on the unlaundered fabric of
this invention.
[0111] Report 1: Fabric of Invention submitted to 12 second
vertical flammability, NFPA 70:2009 Standard for Electrical Safety
in the Workplace, ASTM D 6413 Standard Test Method Flame Resistance
of Textiles (Vertical Test) and ASTM F 1506 Standard Performance
Specification for Flame Resistant Textile Materials for Wearing
Apparel for Use by Electrical Workers Exposed to Momentary Electric
Arc and Related Thermal Hazards paragraph 130.7. The material
weight was 7.4 oz/yd. The tests were performed prior to laundering
as a reference point for subsequent tests after 25 and 100
launderings. 10 specimens of the woven fabric were tested according
to the following criteria with the corresponding results: [0112] 5
specimens were tested lengthwise and 5 specimens were tested
widthwise. [0113] After 12 seconds of a calibrated flame: [0114]
There was no after flame for all 10 samples (2 seconds is the
allowable limit) [0115] There was no afterglow for all 10 samples
[0116] The allowable char length for the test is 152 mm [0117] The
5 lengthwise specimens averages 17 mm (roughly 10% of the allowable
limit) [0118] The 5 widthwise specimens averaged 15 mm (roughly 10%
of the allowable limit) [0119] There was no melting or dripping
Report 2 Certified Test Report for NFPA 70E 2009 (Vertical Flame
Test) from an independent testing lab on the fabric of this
invention after 25 launderings.
[0120] Report 2: Fabric of Invention submitted to 12 second
vertical flammability, NFPA 70:2009 Standard for Electrical Safety
in the Workplace, ASTM D 6413 Standard Test Method Flame Resistance
of Textiles (Vertical Test) and ASTM F 1506 Standard Performance
Specification for Flame Resistant Textile Materials for Wearing
Apparel for Use by Electrical Workers Exposed to Momentary Electric
Arc and Related Thermal Hazards paragraph 130.7. The material
weight was 7.4 oz/yd. The tests were performed after 25 launderings
according to the following criteria with the corresponding results:
[0121] 5 specimens were tested lengthwise and 5 specimens were
tested widthwise. [0122] After 12 seconds of a calibrated flame:
[0123] There was no after flame for all 10 samples (2 seconds is
the allowable limit) [0124] There was no afterglow for all 10
samples [0125] The allowable char length for the test is 152 mm
[0126] The 5 lengthwise specimens averages 14 mm (roughly 10% of
the allowable limit) [0127] The 5 widthwise specimens averaged 11
mm (roughly 10% of the allowable limit) [0128] There was no melting
or dripping Report 3 Certified Test Report for NFPA 70 E 2009
(Vertical Flame Test) from an independent testing lab on the fabric
of this invention after 100 launderings.
[0129] Report 3: Fabric of Invention submitted to 12 second
vertical flammability, NFPA 70:2009 Standard for Electrical Safety
in the Workplace, ASTM D 6413 Standard Test Method Flame Resistance
of Textiles (Vertical Test) and ASTM F 1506 Standard Performance
Specification for Flame Resistant Textile Materials for Wearing
Apparel for Use by Electrical Workers Exposed to Momentary Electric
Arc and Related Thermal Hazards paragraph 130.7. The material
weight was 7.4 oz/yd. The tests were performed after 100
launderings according to the following criteria with the
corresponding results: [0130] 5 specimens were tested lengthwise
and 5 specimens were tested widthwise. [0131] After 12 seconds of a
calibrated flame: [0132] There was no after flame for all 10
samples (2 seconds is the allowable limit) [0133] There was no
afterglow for all 10 samples [0134] The allowable char length for
the test is 152 mm [0135] The 5 lengthwise specimens averages 24 mm
(roughly 20% of the allowable limit) [0136] The 5 widthwise
specimens averaged 18 mm (roughly 20% of the allowable limit)
[0137] There was no melting or dripping Report 4 Certified Test
Report for NFPA 2112 2007 (Thermal Protective Performance) from an
independent testing lab on the fabric of this invention unlaundered
and after 25 launderings.
[0138] Report 4: Fabric of Invention submitted to Thermal
Protective Performance (TPP) Test, NFPA 2112:2007 Standard on Flare
Resistant Garments for Protection of Industrial Personnel Against
Flash Fire, Section 8.2. The TPP value is based on a theoretical
level of thermal protection based on time versus heat exposure.
During the test the specimen is placed between a calibrated heat
source and a calorimeter. The longer it takes the sensing
calorimeter to heat up the higher the TPP value. The higher the TPP
value the longer the exposure until a second degree burn is
experienced. The material weight was 7.4 oz/yd. The tests were
performed on new fabric and after 25 launderings according to the
following criteria with the corresponding results: [0139] 3
specimens were tested with the measurement instrument contacting
the fabric and with an air gap. [0140] Exposure energy was
calibrated at 2.0+/-0.11 cal/cm.sup.2 [0141] Initial specimens (no
laundering) were tested: [0142] Average value of the three
specimens with air gap was 14.2 cal/cm.sup.2 (allowable minimum TPP
6 cal/cm.sup.2) [0143] Average value of the three specimens
contacting fabric was 9.1 cal/cm.sup.2 (allowable minimum TPP 3
cal/cm.sup.2) [0144] 25 Laundering specimens were tested: [0145]
Average value of the three specimens with air gap was 14.8
cal/cm.sup.2 (allowable minimum TPP 6 cal/cm.sup.2) [0146] Average
value of the three specimens contacting fabric was 10.1
cal/cm.sup.2 (allowable minimum TPP 3 cal/cm.sup.2) Report 5
Certified Test Report for NFPA 2112 2007 (Heat and Thermal
Shrinkage Resistance) from an independent testing lab on the fabric
of this invention unlaundered.
[0147] Report 5: Fabric of Invention submitted to Heat and Thermal
Shrinkage Resistance Test, NFPA 2112:2007 Standard on Flame
Resistant Garments for Protection of Industrial Personnel Against
Flash Fire, Section 8.4. Three specimens were selected and were
subjected to the test at three different locations 255 mm.times.255
mm on each specimen at 500 degrees C. This test was performed on
new fabric. The requirements are that the fabric does not shrink
more than 10% (25.5 mm) in any direction and shall not melt, drip,
separate or ignite. The report shows that there was no shrinkage (0
mm) and no melting, dripping, separation or igniting of the
fabric.
Report 6 Certified Test Report for NFPA 2112 2007 (Heat and Thermal
Shrinkage Resistance) from an independent testing lab on the fabric
of this invention after 25 launderings
[0148] Report 6: Fabric of Invention submitted to Heat and Thermal
Shrinkage Resistance Test, NFPA 2112:2007 Standard on Flame
Resistant Garments for Protection of Industrial Personnel Against
Flash Fire, Section 8.4. Three specimens were selected and were
subjected to the test at three different locations 255 mm.times.255
mm on each specimen at 500 degrees C. This test was performed on
fabric after 25 launderings. Note that the specification only
requires 3 launderings. The requirements are that the fabric does
not shrink more than 10% (25.5 mm) in any direction and shall not
melt, drip, separate or ignite. The report shows that there was no
shrinkage (0 mm) and no melting, dripping, separation or igniting
of the fabric.
Report 7 Certified Test Report for FAA FAR 25.853 (a)&(b) (12
Second Vertical Flame Test) from an independent testing lab on the
fabric of this invention after 100 launderings
[0149] Report 7: Fabric of Invention submitted to 12 Second
Vertical Flame Test FAA FAR 25.853 (a)&(b). Six specimens were
selected and split between to measurement machines. The average
burn length for each machine was 0.9'' and 0.7'' which was only 12%
of the allowable char length for the test of 6.0''. The test
results for after flame was 0 seconds against an allowable result
of 15.0 seconds. The drip burn results was zero seconds against an
allowable result of 5.0 seconds.
Report 8 Certified Test Report for FAA FAR 25.853 (a)&(b) (60
Second Vertical Flame Test) from an independent testing lab on the
fabric of this invention after 100 launderings
[0150] Report 8: Fabric of Invention submitted to 60 Second
Vertical Flame Test FAA FAR 25.853 (a)&(b). Six specimens were
selected and split between to measurement machines. The average
burn length for each machine was 1 .3'' and 1.5'' which was only
25% of the allowable char length for the test of 6.0''. The test
results for after flame was 0 seconds against an allowable result
of 15.0 seconds. The drip burn results was zero seconds against an
allowable result of 5.0 seconds.
EXAMPLE 2
Current State of the Art
[0151] A blend of fibers, commercially available under the Dupont
trade names NOMEX.RTM. (meta-aramid) and KEVLAR.RTM. (para-aramid)
provided in a Dupont fabric Protera.TM. totaling 33 wt % NOMEX.RTM.
and KEVLAR.RTM., 65% modacrylic and 2% antistatic in a single layer
twill weave at 6.8 oz/sq yd, similar to, but not in the same wt %
of meta-aramid and para-aramid as the invention disclosed
herein.
Report 9 Certified Test Report for NPPA 70E 2009 (Vertical Flame
Test) from an independent testing lab on Dupont Protera.TM. fabric
as an example of the state of the art.
[0152] Report 9: Dupont Protera.TM. submitted to 12 second vertical
flammability, NFPA 70:2009 Standard for Electrical Safety in the
Workplace, ASTM D 6413 Standard Test Method Flame Resistance of
Textiles (Vertical Test) and ASTM F 1506 Standard Performance
Specification for Flame Resistant Textile Materials for Wearing
Apparel for Use by Electrical Workers Exposed to Momentary Electric
Arc and Related Thermal Hazards paragraph 130.7. The material
weight was 6.8 oz/yd. The tests were performed prior to laundering.
10 specimens of the woven fabric were tested according to the
following criteria with the corresponding results: [0153] 5
specimens were tested lengthwise and 5 specimens were tested
widthwise. [0154] After 12 seconds of a calibrated flame: [0155]
There was no after flame for all 10 samples (2 seconds is the
allowable limit) [0156] There was an average afterglow of 2.5
seconds [0157] The allowable char length for the test is 152 mm
[0158] The 5 lengthwise specimens averages 91 mm (roughly 65% of
the allowable limit) [0159] The 5 widthwise specimens averaged 87
mm (roughly 65% of the allowable limit) [0160] There was no melting
or dripping The first example of current state of the art, Dupont
Protera.TM., displayed significantly different NFPA 70E test
results in fabric performance from this invention. The direct
comparison between the test results for this invention in Report 1
and the test results for Dupont Protera.TM. shows two distict
differences in afterglow and fabric char length. There was no
afterglow for the invention and an average afterglow of 2.5 seconds
for Dupont Protera.TM.. Although the test criteria allows afterglow
for 10 seconds, after glow indicates that the fibers are being
charred which makes the fibers brittle. The char length is the
dimension for fabric that has charred. The greater the char length,
the more the fabric becomes brittle and eventually the fabric
breaks exposing whatever is underneath directly to flame and heat.
The char length for the invention was an average of 16 mm or
approximately 10% of the allowable limit for the test. The char
length of Dupont Protera.TM. was an average of 89 mm, 5.5 times
greater than the invention and 65% of the allowable limit for the
test. Report 10 Certified Test Report for FAA FAR 25.853
(a)&(b) (60 Second Vertical Flame Test) from an independent
testing lab on Dupont Protera.TM. fabric as an example of the state
of the art.
[0161] Report 10: Dupont Protera.TM. submitted to 60 Second
Vertical Flame Test FAA FAR 25.853 (a)&(b). Six specimens were
selected and split between to measurement machines. The average
burn length for each machine was 4.3'' and 4.0'' and 70% of the
allowable char length for the test of 6.0''. The test results for
after flame was 0 seconds against an allowable result of 15.0
seconds. The drip burn results was zero seconds against an
allowable result of 5.0 seconds.
[0162] The first example of current state of the art, Dupont
Protera.TM., displayed significantly different FAA FAR test results
in fabric performance from this invention. The difference between
this test and the NFPA 70E test is that the exposure time is
increased from 12 to 60 seconds and there is no measurement for
afterglow. In addition, the invention was tested after 100
launderings where the Dupont Protera.upsilon. was tested before
laundering. The char length for the invention was an average of 1.4
in or approximately 25% of the allowable 6.0 in limit for the test.
The char length of Dupont Protera.TM. was an average of 4.2 in,
nearly 4 times greater than the invention and 70% of the allowable
limit for the test.
EXAMPLE 3
Current State of the Art
[0163] A blend of fibers, commercially available under the Dupont
trade names NOMEX.RTM. (meta-aramid) and KEVLAR.RTM. (para-aramid)
provided in Dupont fabric NOMEX.RTM. IIIA totaling 93 wt %
NOMEX.RTM., 5 wt % KEVLAR.RTM. and 2 wt % anti static in a single
layer twill weave at 8.0 oz/sq yd similar to, but not in the same
wt % of meta-aramid and para-aramid as the invention disclosed
herein.
Report 11 Certified Test Report for NPPA 70E 2009 (Vertical Flame
Test) from an independent testing lab on Dupont NOMEX IIIA.TM.
fabric as an example of the state of the art.
[0164] Report 11: Dupont NOMEX.RTM. IIIA submitted to 12second
vertical flammability, NFPA 70:2009 Standard for Electrical Safety
in the Workplace, ASTM D 6413 Standard Test Method Flame Resistance
of Textiles (Vertical Test) and ASTM F 1506 Standard Performance
Specification for Flame Resistant Textile Materials for Wearing
Apparel for Use by Electrical Workers Exposed to Momentary Electric
Arc and Related Thermal Hazards paragraph 130.7. The material
weight was 8.0 oz/yd. The tests were performed prior to laundering.
10 specimens of the woven fabric were tested according to the
following criteria with the corresponding results: [0165] 5
specimens were tested lengthwise and 5 specimens were tested
widthwise. [0166] After 12 seconds of a calibrated flame: [0167]
There was no after flame for all 10 samples (2 seconds is the
allowable limit) [0168] There was no afterglow [0169] The allowable
char length for the test is 152 mm [0170] The 5 lengthwise
specimens averages 66 mm (roughly 43% of the allowable limit)
[0171] The 5 widthwise specimens averaged 58 mm (roughly 38% of the
allowable limit) [0172] There was no melting or dripping [0173] The
second example of current state of the art, Dupont NOMEX.RTM. IIIA,
displayed significantly different NFPA 70E test results in fabric
performance from this invention. The direct comparison between the
test results for this invention in Report 1 and the test results
for Dupont NOMEX.RTM. IIIA shows a distinct difference in fabric
char length. The char length is the dimension for fabric that has
charred. The greater the char length, the more the fabric becomes
brittle and eventually the fabric breaks exposing whatever is
underneat directly to flame and heat. The char length for the
invention was an average of 16 mm or approximately 10% of the
allowable limit for the test. The char length of Dupont Protera.TM.
was an average of 62 mm, nearly 4 times greater than the invention
and 41% of the allowable limit for the test. Report 12 Certified
Test Report for FAA FAR 25.853 (a)&(b) (60 Second Vertical
Flame Test) from an independent testing lab on Dupont NOMEX
IIIA.TM. fabric as an example of the state of the art.
[0174] Report 12: Dupont NOMEX.RTM. IIIA submitted to 60 Second
Vertical Flame Test FAA FAR 25.853 (a)&(b). Six specimens were
selected and split between to measurement machines. The average
burn length for each machine was 2.8'' and 3.2'' and 50% of the
allowable char length for the test of 6.0'. The test results for
after flame was 0 seconds against an allowable result of 15.0
seconds. The drip burn results was zero seconds against an
allowable result of 5.0 seconds.
[0175] The second example of current state of the art, Dupont
NOMEX.RTM. IIIA displayed significantly different FAA FAR test
results in fabric performance from this invention. The difference
between this test and the NFPA 70E test is that the exposure time
is increased from 12 to 60 seconds and there is no measurement for
after glow. In addition, the invention was tested after 100
launderings where the Dupont NOMEX.RTM. IIIA was tested before
laundering. The char length for the invention was an average of 1.4
in or approximately 25% of the allowable 6.0 in limit for the test.
The char length of Dupont Protera.TM. was an average of 3.0 in,
twice the charring of the invention and 50% of the allowable limit
for the test.
[0176] The certified test results show a yarn construction when
simply woven that has exceptional properties for protection from
heat, flame and electric arc protection while having no shrinkage,
melting, dripping separation, after flame, after glow or ignition.
In addition the test results show no degredation in protection from
laundering, even at 100 cycles.
[0177] The flame and heat resistance is significantly better that
the current state of the art products of similar fabric weight and
weave comprised of the same materials of meta-aramid and
para-aramid fibers. Clearly the higher wt % of para-aramid fibers
blended with meta-aramid fibers as well as the unique method of
making the yarn contributes to the desired and stated performance
of the invention disclosed herein. This invention can also be made
at lighter fabric weights and still provide the flame and thermal
protection of heavier weight fabrics. The lighter weight fabric
will also contribute to increased flexibulity and articulation
while reducing heat stress caused by heavier weight fabrics and
restricted body movement casued by heavier weight fabrics made with
para-aramids blended with meta-aramids.
[0178] The present disclosure includes that contained in the
appended claims, as well as that of the foregoing description.
Although this invention has been described in its preferred form
with a certain degree of particularity, it is understood that the
present disclosure of the preferred form has been made only by way
of example and that numerous changes in the details of construction
and the combination and arrangement of parts may be resorted to
without departing from the spirit and scope of the invention.
* * * * *