CROSS-REFERENCETORELATEDAPPLICATION This application claims priority to U.S. utility application entitled

"BLENDED OUTER SHELL FABRICS" filed on October 19, 2004, and no

serial number has yet to be assigned, and is entirely incorporated herein by

reference.

BACKGROUND

Firefighters typically wear protective garments commonly referred to in

the industry as turnout gear. Turnout gear normally comprises various

garments including, for instance, coveralls, trousers, and jackets. These

garments usually include several layers of material including, for example, an

outer shell that protects the wearer from flames, a moisture barrier that

prevents the ingress of water into the garment, and a thermal barrier that

insulates the wearer from extreme heat.

Turnout gear outer shells typically comprise woven fabrics formed of

one or two types of flame resistant materials. In addition to shielding the

wearer from flames, the outer shells of firefighter turnout gear further provide

abrasion resistance and protection from sharp objects, hi that the outer shell

must withstand exposure to flame and excessive heat, and must be resistant to

abrasion and tearing, it must be constructed of a flame resistant material that is

both strong and durable.

The selection process for the materials used to construct outer shell

fabrics, as with the selection process for other fabrics, often involves balancing

various factors. Such factors include fabric performance as well as cost. For

instance, outer shell fabrics that primarily comprise lower-performance fibers

are normally less expensive than fabrics that include higher-performance

fibers. Although the fabrics that comprise higher-performance fibers may

provide greater protection, that protection comes at a greater cost, both to the manufacturer and the consumer.

In view of the above, it would be desirable to be able to provide

relatively inexpensive outer shell fabrics having performance that approaches or even exceeds that of more expensive outer shell fabrics.

SUMMARY

The present disclosure relates to blended outer shell fabrics, hi one

embodiment, an outer shell fabric for use in firefighter turnout gear includes a

plurality of yarns that comprise at least three different types of inherently

flame resistant fibers.

hi another embodiment, a fabric includes a blend of inherently flame

resistant fibers, the blend including a plurality of para-aramid fibers, a plurality of meta-aramid fibers, and a plurality of polybenzoxazole (PBO) fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed fabrics can be better understood with reference to the

following drawings. The components in the drawings are not necessarily to scale.

FIG. 1 is a rear view of an example protective garment that includes a

blended outer shell fabric.

FIG. 2 is a schematic representation of a blended outer shell fabric that can be used in the construction of the garment of FIG. 1.

FIG. 3 is a schematic representation of an alternative blended outer shell

fabric that can be used in the construction of the garment of FIG. 1.

DETAILED DESCRIPTION

As is described in the foregoing, it would be desirable to be able to provide relatively inexpensive outer shell fabrics having improved

performance. As is described in the following, such a result can be achieved with certain blends of inherently flame resistant fibers. One such blend, for

example, includes a blend of para-aramid, meta-aramid, and polybenzoxazole

(PBO) fibers. As is described in greater detail below, such a blend provides

unexpectedly desirable physical properties at a relatively low cost.

FIG. 1 illustrates an example protective garment 100. More

particularly, FIG. 1 illustrates a firefighter turnout coat that can be donned by

firefighter personnel when exposed to flames and extreme heat. It is noted that, although a firefighter turnout coat is shown in the figure and described

herein, embodiments of this disclosure pertain to protective garments and

fabrics generally. Accordingly, the identification of firefighter turnout gear is

not intended to limit the scope of the disclosure.

As is indicated in FIG. 1, the garment 100 generally comprises an outer

shell 102 that forms the exterior surface of the garment, a moisture barrier 104

that forms an intermediate layer of the garment, and a thermal liner 106 that

forms the interior surface (i.e., the surface that contacts the wearer) of the

garment. In that it forms the exterior surface of the garment 100, the outer

shell 102 preferably is constructed so as to be flame resistant to protect the

wearer against being burned. In addition, the outer shell 102 preferably is

strong and durable so as to be resistant to abrasion and tearing during use in hazardous environments.

FIG. 2 is a schematic detail view of an example blended outer shell

fabric 200 that can be used in the construction of the protective garment 100,

and more particularly the outer shell 102 shown in FIG. 1. It is noted,

however, that the fabric 200 could be used in the construction of other protective garments either by itself or in combination with other fabrics. The

example fabric 200 illustrated in FIG. 2 is a rip stop fabric that comprises a plurality of body yarns 206, including picks 202 and ends 204, and a plurality

of rip stop yarns 208. Although a rip stop weave is illustrated in FIG. 2 and is

described herein, it will be appreciated that other configurations could be used

including, for instance, a plain weave, a twill weave, or a variation on a

conventional rip stop weave (see, e.g., FIG. 3).

Generally speaking, the fabric 200 comprises a blend of different

inherently flame resistant materials. Typically, at least three different inherently flame resistant materials are used to construct the fabric 200 so as to

obtain the distinct benefits of each, whether they be performance or cost

benefits. By way of example, the yarns of the fabric 200, including one or

more of the picks 202, ends 204, and rip stop yarns 208, comprise a blend of

para-aramid fibers, meta-aramid fibers, and PBO fibers.

Example para-aramid fibers include those that are currently available

under the trademarks KEVLAR ^® (DuPont), and TECHNORA ^® and

TWARON ^® (Teijin). Example meta-aramid fibers include those sold under

the tradenames NOMEX T-450 ^® (100% meta-aramid), NOMEX T-455 ^® (a

blend of 95% NOMEX ^® and 5% KEVLAR ^® ), and NOMEX T-462 ^® (a blend

of 93% NOMEX ^® , 5% KEVLAR ^® , and 2% anti-static carbon/nylon), each of

which is produced by DuPont. Example meta-aramid fibers also include fibers

that are currently available under the trademarks CONEX ^® and APYEBL ^® ,

which are produced by Teijin and Unitika, respectively. Example PBO fibers

include ZYLON ^® from Toyobo ^® .

It is noted that, for purposes of the present disclosure, when a material

name is used herein, the material referred to, although primarily comprising the named material, may not be limited to only the named material. For

instance, the term "meta-aramid fibers" is intended to include NOMEX ^® T-

462 fibers, which, as is noted above, comprise relatively small amounts of

para-aramid fiber and anti-static fiber in addition to fibers composed of meta-

aramid material.

While a tri-blend of para-aramid, meta-aramid, and PBO fibers has been explicitly identified, other inherently flame resistant materials can be

added to the blend, if desired. Such other materials may, for example, include

one or more of polybenzimidazole (PBI), melamine, polyamide, polyimide,

polyimideamide, and modacrylic.

Moreover, non-mherently flame resistant materials can be added to the

blend, if desired. Examples of such materials include cellulosic fibers, such as

rayon, acetate, triacetate, and lyocell. These cellulosic materials, although not naturally resistant to flame, can be rendered flame resistant, if desired.

hi cases in which para-aramid, meta-aramid, and PBO fibers are used

to construct the fabric 200, the fabric can, for example, comprise about 40% to

about 70% para-aramid, about 10% to about 40% meta-aramid, and about 5%

to about 30% PBO. As is described below, one example blend is an

approximately 60/20/20 blend of para-aramid fibers, meta-aramid fibers, and

PBO fibers, respectively.

The body yarns 206 typically comprise spun yarns that, for example,

each comprises a single yarn or two or more individual yarns that are plied, or

otherwise combined, together. By way of example, the body yarns 206 comprise one or more yarns that each have a yarn count (or "cotton count") in

the range of approximately 5 to 60 cc, with 8 to 40 cc being preferred, hi some embodiments, the body yarns 206 can comprise two yarns that are plied

together, each having a yarn count in the range of approximately 10 to 35 cc.

The rip stop yarns 208 can have a construction similar to those of the

body yarns, but are provided in pairs that are woven through the fabric 200

side-by-side as is illustrated in FIG. 2. hi some embodiments, rip stop yarns

208 can be different in construction from the body yarns 206. For example, filament yarns could be used in the construction of the rip stop yarns 208, if

desired, hi other embodiments, filament yarns can be combined with spun

yarns or spun fiber to form rip stop yarns in the manner described in U.S.

Patent Application No. 10/165,795, which is hereby incorporated by reference

into the present disclosure, hi cases in which the rip stop yarns 208 have a

construction that is different than the body yarns 206, it is possible to use a

single yarn instead of two as is illustrated in FIG. 2. For example, if the rip

stop yarns 208 have a lower yarn count (and therefore larger size) than the

body yarns 206, then single rip stop yarns 208 may be enough to protect

against propagation of fabric tears.

The placement of the rip stop yams 208 within the fabric 200 can be

varied depending upon the desired physical properties, hi the embodiment

shown in FIG. 2, the rip stop yarns 208 are provided within the fabric 200 in a

grid pattern in which several body yarns 206 are placed between each

consecutive pair of rip stop yarns 208 in both the warp and filling directions of the fabric. By way of example, a pair of rip stop yarns 208 is provided in the

fabric 200 in both the warp and filling directions of the fabric for every

approximately 7 to 9 body yarns 206. hi some embodiments, the grid pattern is configured to form a plurality of squares. To accomplish this, a greater

number of body yarns 206 may need to be provided between consecutive rip

stop yarn pairs in the one direction (e.g., warp) as compared to the other

direction (e.g., filling).

FIG. 3 is a schematic detail view of an alternative example rip stop

fabric 300 that can be used in the construction of the protective garment 100.

The fabric 300 is similar to the fabric 200 shown in FIG. 2 and therefore, comprises body yarns 206 that form the body of the fabric and that have

composition and construction similar to those described above with regard to

FIG. 2. In the fabric 300, however, three rip stop yarns 208 are woven through

the fabric together in a grid pattern within the fabric body to form a three-end

rip stop weave (as opposed to the two-end rip stop weave shown in FIG. 2).

With the constructions described above, the fabrics 200, 300 have

weights of about 5 to about 10 ounces per square yard (osy).

As is noted above, unexpected results are achievable with the blends

described herein. More specifically, unexpectedly desirable physical

properties can be attained given the relatively low cost of the fabric, which is

dictated, in substantial part, by the cost of the materials used to produce the

fabric. In several instances, the physical properties of the disclosed blends exceed (i.e., are better than) those of competing fabrics and are substantially

lower in cost than "top-end" outer shell fabrics. A specific example fabric

having a construction within the parameters identified in the foregoing is

described in the following.

Example Fabric

A 60/20/20 blend of KEVLAR ^® T-970 (para-aramid), NOMEX ^® T-462

(meta-aramid), and ZYLON ^® (PBO) was constructed having a fabric weight of

approximately 7.5 osy. The fabric was formed as a two-end rip stop fabric

(see, e.g., FIG. 2) having 56 ends per inch and 51 picks per inch, with 9 ends

provided between each pair of rip stop yarns in the warp direction, and 7 picks

provided between each pair of rip stop yarns in the filling direction. Each of

the yarns in the fabric (i.e., body and rip stop yarns in both directions) comprised two 60/20/20 KEVLAR ^® /NOMEX ^® /ZYLON ^® yarns each having a

yarn count of 21 cc (i.e., 21/2 yarns).

Once constructed, the example fabric was tested to determine its

physical and thermal properties. The results of the testing are provided in

Table I, in which the example fabric is designated as the "Tri-Blend Fabric."

Also included in this table are the test results for other fabrics ("Comparison

Fabrics A and B").

Comparison Fabric A comprised a 60/40 blend of KEVLAR ^® T-970

and NOMEX ^® T-462 having a fabric weight of approximately 7.2 osy. The

fabric was formed as a three-end rip stop fabric having 56 ends per inch and 51

picks per inch, with 8 ends provided between each group of three rip stop

yarns in the warp direction, and 8 picks provided between each group of three

rip stop yarns in the filling direction. Each of the yarns in the fabric (i.e., body

and rip stop yarns in both directions) comprised two 60/40

KEVLAR ^® /NOMEX ^® yarns each having a yarn count of 21 cc (i.e., 21/2

yarns).

Comparison Fabric B comprised a 60/40 blend of KEVLAR ^® T-970 and PBI having a fabric weight of approximately 7.5 osy. The fabric was

formed as a two-end rip stop fabric having 44 ends per inch and 39 picks per

inch, with 9 ends provided between each pair of rip stop yarns in the warp

direction, and 7 picks provided between each pair of rip stop yarns in the

filling direction. Each of the yarns in the fabric (i.e., body and rip stop yarns

in both directions) comprised two 60/40 KEVLAR ^® /PBI yarns each having a

yarn count of 15 cc (i.e., 15/2 yarns).

As is indicated in Table I, the example fabric and the comparison fabrics were tested for strength, thermal resistance, and abrasion resistance, hi

terms of strength, the trap tear strength of the fabrics was tested according to

test method ASTM D5733, as is required by NFPA 1971, 2000 edition

(hereafter "NFPA 1971"), both before and after 5 washing cycles, hi addition,

the fabrics were separately tested for tensile strength according to test method

ASTM D5034 prior to washing and thermal exposure, after 10 washing cycles,

and after thermal exposure. hi terms of thermal resistance, the fabrics were exposed to extreme

temperatures for seven (7) seconds in accordance with the thermal protective

performance (TPP) test method described in NFPA 1971, and were tested for

vertical flame in accordance with Federal Test Method 191 A as is required by

NFPA 1971.

Finally, the fabrics were tested for abrasion resistance using the Taber

Abrasion Test in accordance with ASTM3884.

TABLE T

As is evident from Table I, the example fabric ("Tri-Blend Fabric")

performed markedly better in terms of both trap tear strength and tensile

strength than Comparison Fabrics A and B. Although improved performance

could be expected over Comparison Fabric A due to the presence of the PBO

fiber in the Tri-Blend Fabric, the magnitude of the strength increases resulting

from only 20% PBO fiber is particularly surprising. For instance, the tensile

strength of the Tri-Blend Fabric tested to be as much as over 250% greater

than that of Comparison Fabric A.

Equally or even more surprising is the strength that the Tri-Blend

fabric exhibited after 7 seconds of TTP exposure as compared to Comparison

Fabric B. As is evident from the table, the Tri-Blend fabric was approximately

twice as strong as Comparison Fabric B after such exposure. This strength

difference was unexpected at least in part because Comparison Fabric B

contained a significant amount of PBI, which is generally regarded as much

more resistant to thermal exposure than less expensive materials, such as the meta-aramid of the Tri-Blend fabric.

In addition, marked improvement in abrasion resistance was observed

for the Tri-Blend Fabric. As is indicated in Table I, the Tri-Blend Fabric exhibited an abrasion resistance that is nearly three times that of Comparison

Fabrics A and B.

Notably, the above-described high strength and abrasion resistance is

achievable with a fabric that is significantly cheaper to produce than many

high-end fabrics, such as Comparison Fabric B, which comprises relatively

costly PBI fiber. Therefore, a high-strength, abrasion-resistant, and flame resistant fabric can be produced at a relatively low cost.

While particular embodiments of fabrics have been disclosed in detail in

the foregoing description and drawings for purposes of example, it will be

understood by those skilled in the art that variations and modifications thereof

can be made without departing from the scope of the disclosure.