CA1296609C

CA1296609C - Almost impermeable chemically protective fabric

Info

Publication number: CA1296609C
Application number: CA000578467A
Authority: CA
Inventors: Randall J. Osczevski; Brian Farnworth
Original assignee: Minister of National Defence of Canada
Current assignee: Minister of National Defence of Canada
Priority date: 1988-09-26
Filing date: 1988-09-26
Publication date: 1992-03-03
Anticipated expiration: 2009-03-03
Also published as: US4981738A

Abstract

ABSTRACT
This invention relates to a multi-layer protective fabric for protective suits used in hazardous or toxic environments. A first layer comprises strips of water and vapour impermeable material, there being a gap between adjacent such strips. A second layer comprises a plurality of strips of a wicking material with each such strip covering the inner surface of a first layer strip, passing through the gap between adjacent strips and covering the outer surface of the adjacent first layer strip. Moisture, such as perspiration will pass via the wicking material through the gaps past the first layer for evaporation and diffusion through a third layer of a liquid impermeable/vapour permeable material which extends over the second layer material covering the outer surfaces of the first layer.

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Description

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The present invention relate3 to protective fabric~
for use in hazardous environments and to protective suits ; manufactured from such fabrics.
BACKGROUND OF THE INVENTION
Protective suits are worn by both clvilian and military personnel whenever there is a chance of exposure to hazardous environments such as toxic chemicals or vapours, or nuclear, biological or chemical tNBCj warfare situations.

~ Such suits must be impermeable to the toxic or harmul vapours .~ ~
but, as a consequence,~such suits quickly become uncomfortable to wear because they do not allow for adequate evaporation of perspiration.; Su~its which~are ~ermeable~to vapours may include a layer of~activated charcoal for absorbing harmful agents but with;time~and~use the absorptlve capacity of the cha;rcoal becomes saturated with water by various organic components of perspiration or by chemical ayents. Thus the useful life of a vapour permeable suit, which permits the slow evaporatlon of perspiration, is limited by the useful lie of the aativated charcoal. There i~ thereEore a need for a ~20 protective suit made ~rom a fabric that will permit eficient removal of perspiratioll and thereby improve the interior enVironment o~ the ~uit for the wearer.
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The present invention provides a mul~i~Iayer fabric whl~ch:~is impermeable~to liquids~ls impermeable to alr ; ; cur~rents; is~impermeable to~ r has a very low permeability t~o,~most~vapours;~and~whi;ch~wlll pass~ water or moistu e by a rn/rm ~ ~ ~

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combination oE liquid wicking and vapour diffusion.
The multi-layer protectlve fabric of this invention include a first or barrier layer formed from strips of a liquid and vapoUr lmpermeable material~ there being a slight gap between adjacent first layer strips. A second layer includes a plurality of strips of wicking ma~erial with each second layer strip covering an inner surface of one first ; layer strip, extending through the gap between adjacent first layer strips and covering the outer surface oE the adjacent first layer strip. The third layer is formed of a liquid ~; impermeable/vapour permeable material and extends over the second layer~material that~covers the outer surfaces of the first layer material. If desired a fourth layer of a fabric material can coyer the t~hird layer for reinforcement purposes.
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When a protective suit made from the fabric of this invention is in use, ~he innermost wicking material of the second layer will absorb perspiration from the skin oE the wearer and when it is saturated thereby the moisture Will be carried through the gaps between ad~acent strips oE the first .:
layer to the outermost wicking material of the second layer from which it will evaporate and dlfuse through the third layer r carrying with it lts latent heat of vaporization and cooling the body o~ the wearer.
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~ Other ~eatures of the preserlt invention will become I
apparent ~rom the~description which follows.

BRIEF_DESCRIPTION OF_THE DRAWINGS

Figure~ illustrates yenerally a protective suit as rn/:r-m : , : ` :

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might be made by the protective fabric of this invention.
Figure 2 illustrates in perspective a portion of the protective fabric of this invention.
Figure 3 shows a section of the fabric taken on the line 3-3 of Figure 2.
Figure 4 shows a slight1y exploded view of Figure 3.
Figure 5 shows a slightly exploded view, similar to Figure 41 of a second embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
~ Figure l il1ustrates generally a protective suit l0 which might be worn in conditions oE nuclear, biological or chemical (NBC) warfare or which might be worn by anyone workiny normally with hazardous (e.g. toxic) materials. Such a suit is designed to be generally impervious to the dangerous material and it will be integrally formed with torso, legl arm' boot and gIove portions 12, 14, 16, l81 20 respectively.
A helmet 22 is sealingly connectable to the suit. The number of seams is kept to a minimum so as to present the least number of avenues by which dangerous material could breach the lntegrity of the 9uit.
A protectlve suit that ef~ectively prevents the intrusion o~ vapours, liquids or gases will, perforce, present problems with respect to the dissipation oE internal moisture, such as perspiration, making the interior of the suit very uncomfortable over long periods of time, especially in hiyh ambient temperatures. The fabric of the present invention is , intended to improve the cllmatic condltions within such a suit rn/rm ., ~ . . . .
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so that the wearer of such a suit may per~orm hls tasks without any great concern respecting personal comfort.
One embodiment of the fabric of the present invention is illustrated schematically in Figures 2 to 4, it being understood that large sheets o the material would be provided for subsequent manufacture into protective suits or portions thereof. For example, it might be necessary to make only the arms and gloves o a protective suit from the material of the present invention if only the arms and gloves will be subjected to hostile environments.
With reference to Figures 2 to 4, it will be seen that the fabric 30 of the present invention includes a -~ plurality of layers of material bonded together by a suitable bonding agent to create a multi~layer effect, The first layer 32 is a barrier layer made from a plurality of strips 34 of a water and vapour impermeable material such as butyl rubber with or without a fabrlc or textile backing, ~he s~rips 34 will be from 10 to 100 mm wide, with an optlmum width ln the order of 20 mm, The s~rips 34 are spaced apar~ 90 as to define a narrow gap 36 between the edges of ad~acent strlps, The first layer 32 will be the main barrier to toxic vapours.
~ he second layer 38 actually appears as two layers buk is considered to be a single layer for the purpose of this description, The layer 38 comprises a plurality of strips 40 ; of a wicking~material, Each strip 40 is interwoven with a pair of adjacent first layer strips 34 such that each second layer strip covers the inner surface 42 o one first layer rn/rm ;6~3 strip, extends through the gap 36 between adjacent first layer strips and covers the outer surface 44 of the adjacent first ; layer strip. It will therefore be seen that: (a) the gap 36 has a width approximately equal to the thickness of the second layer wicking material; (b) each second layer ~trip has a width approximately double the width of a first layer strip;
and (c) when the first and second layers are woven together both the inner and outer surfaces of the first layer will be covered by second layer wicking material, with connections between the second layer coverings being achieved by the material portions that pass through the gaps 36.
The purpose of the wicking material of the second layer 38 is to provide a path for the transfer of moisture such as perspiration through the first or barrier layer 32.

i Thus each strip 40 should be formed from a material which wicks well but is as thin as possible. Suitable materials :
; aould be woVen or knitted Eabrics of nylon, polyester, polypropylene-, or blends thereo~ with cotton or nonwoven fibrous materials having a paper-like structurel as long as such Eibrous materials have been surEace-treated to make them wettable. A thin fabric, rather than a ~hick Eabric, is desired since a thin material has a lower threshold at which ; wicking will commence.
A third layer 46 is provided in contact with the portions of;the second layer 38 covering the outer surfaces of the first layer. The material of layer 46 is liquid impermeable/vapour permeable and its purpose is to keep liquid rn/rm , . ... . . .

. . , -` ~L29~50 chemicals away Prom the wicklng material ~lnce ~Uch chemlcal~
could be otherwise transported inwardly past the barrier layer 32 in the same way that moisture can wick outwardly. The material of the third layer 46 could be a conventional woven or nonwoven textile fabric which is not really liquid impermeable but which has been treated with a suitable liquid repellent such as ZEPEL-B (trade mark~. If there is concern that the repellency may not be adequate to keep liquids out in the event that the material becomes dirty, is flexed repeatedlyr or is subjected to pressure then an alternative would include a microporous~film or coating such as DERMOFLEX
(trade mark) or GORETEX (trade mark) GENERATION I Such ; substances also rely on repellency to keep liquids out but, because of their miniscule~pore size, they are much more resistant to the penetration of liquids under pressure.
Another alternative is a polymer layer which is not micro-porous but is permeable to the diffusion of water vapour because of the hydrophilic chemical nature of the polymer itself. SUch polymer layers are o~ten used in conjunction with microporous membranes as in DERMOFLEX wi~h an NPU-23 top : , :
coat or in GORETEX GENERATION II. Other such polymers are applied directly to Woven textile fabrics, e.g. STEDTHANE
(trade mark).
Coatings which are microporous have the advantage of ~high v~apour~permeabllity under all conditions. Hydrophilic c~ontinuous~fllms on the other hand are only vapour permeable under very humid condit~ions.~ This is not a disadvantage with rn/rm ,,,,:.~",.",.~, - : ~:

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the present invention since the entire ~abric will only transmit water if the inside is actually wet. Hydrophilic films may be usable in situations where selective permeability is desirable as they are permeable to water vapour but not to simple inoryanic gases such as oxygen or carbon dioxide and they may also be impermeable to certain chemical agents.
The outermost or fourth layer 48 is a conventional woven or knitted fabric and is provided, as necessary, to give strength and abrasion resistance to the overall fabric. There may be instances where a fourth layer is not required, a suitable fabric being composed of only the first three layers as described hereinabove.
The fabric of the present invention has a low permeability to all gases because most of its area consists of the impermeable first layer 32 witb only the gaps 36 being permeable to vapour. Each gap is, ideally, only as wLde as the thickness of the wicking material, about 0.3 mm and thus ;~ the permeability of the fabric of this invention is reduced in comparison with an uncoated fabric oE similar thickness by a factor equal to the ratio oE the strip width to the gap width, a factor of 67 for a first layer strip width of 20 mm and a gap width of 0.3 mm.
The manner in which the fabric of the present invention operates when manufa~tured into a protective suit, ., the foremost application for the fahric, is relatively straightforward~ When worn by an actively perspiring user, the fabric of the suit will become wet on the inside either by rn/rm ', :

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direct transfer of liquid water rom the skin to the wickiny material or by an evaporation/diffusion/condensation process.
When the wicking material 40 covering the inner surfaces 42 of the first layer 32 becomes saturated, water will wick past the layer 32 via the gaps 36 and will then reach the material 40 covering the outer surfaces 44 of the layer 32. From there the water will evapora~e, diffuse through the outer layer(s) 46 (and 48) and escape to the environment, taking with it its latent heat of vaporization and cooling the body. For maximum cooling efficiency, the fabric of this invention should be positioned as closely as possible to the wearer's body. When ~; constructing the suit one could use form-fitting stretch fabrics for the first, third and fourth layers or each suit could be carefully tailored to the body of each specific wearer and thus use non~stretch fabrics.
For general clothing use, the fabric o~ the ~, invention should be as ligh~ in weight as possible, with each layer in the order of 50 g/m2 except for the first (barrier~
layer which can be heavier, gLving a total for the Eabric of 300 to 500 g/m~. Higher fabric weights may be necessary i~
abrasion resistance is a priority. The entLre suit/ or only portions thereo, could be made from ~he fabric of the present invention. ~ heavier version could also be used as boot uppers.
The permeability of the fabric of this invention to chemical vapours should be low when the materials thereof are dry but may be substantially higher when they are wet. If the : ~ :

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chemical agent is insoluble in water, there wlll, of course, be no increase in permeability. However, iE the chemical agent is water soluble, it could be transported past the barrier (first) layer 32 by diffusion in the wa~er-soaked (by perspiration) wicking material. To prevent this, the wicking material may be treated with a material that can absorb or chemically destroy the agent. Since the chemical agent can only penetrate by diffusing over a length of several centi-meters the area of contaminatlon by the chemical agent will be large and only a small quantity of absorbing or reactive substance need be added to the wicking material. ~he absorbing substance can be relatively inefficient when compared to the activated~ charcoal used in existing chemically protective suits and a micro-encapsulated charcoal or a micro encapsulated reactive chemical can be used. This provides the advantage of long shelf life and the freedom from contamina~
tion by perspiration. Existing chemically protective suits use 10 y/m2 to 100 g/m2 of activated charcoal. With the present invention it is estimated that equivalent protection , can be obtained by using from l/100 to l/lO o~ that amount.
Figure 5 illustrates in a partially exploded Eorm an alternative construction for the fabric of this invention~
; ~ Layers 46 and 48, the latter being optional, are the same as for the first embodiment and will not be described any further.
In this embodiment, ~the ~irst or barrier layer 50 comprises a plurality of strips 52 of the same material as rn/rm ,~. , .

strips 34. However, in this case, a portion 54 of each strip 52 along one edge thereof is displaced slightly so tha~ the portion of the inner surface S6 along the portion 54 overlies or overlaps a portion oE the outer surface 58 of an adjacent strip 52. The overlapping portions deflne a gap 60 between the adjacent strips 52. The second, or wicking, layer 62 comprises a plurality of strips 64 of wicking material, each strip covering the inner surface 56 of one first layer strip 52, extending through the gap 60 and covering the outer surface 58 of the adjacent first layer strip, including the overlapping portion 54. The layers are bonded together as in the first embodlment.
The degree of overlap by portion 54 will be in the order o a few millimeters. This ensures that the gap 60 cannot be more than the thickness of the wicking material and with this embodiment the wicking path is lengthened in com-parison to the irst embodiment. With this embodiment the overall permeability of the fabric can be reduced by a Eactor ~; ~ of about 10. The overall permeability is still ur~ther reduced if the third layer 46 offers any substantial resist-ance to the difusion of chemical vapoursu The abric o the present invention provides clear advantages over existing protective fabrics by using wicking materials to pass water through an otherwise impermeable fabric. Two embodime~ts of the fabric of this invention have been described but, undoubtedly, a skilled person in the art could develop other fabric constructions without departing rn/rm , , ., from the spirit of the invention. Thus the scope o~
protection to be afforded this invention is to be determined ~rom the claims appended hereto.

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Claims

1. A protective fabric comprising a plurality of material layers bonded together and including: a first layer formed from a plurality of adjacent strips of liquid and vapour impermeable material, adjacent strips being spaced apart from each other by a slight gap, each first layer strip having an inner surface and an outer surface; a second layer formed from a plurality of strips of wicking material, each second layer strip covering the inner surface of a first layer strip, extending through the gap between adjacent first layer strips, and covering the outer surface of the adjacent first layer strip; and a third layer of liquid impermeable/vapour permeable material extending over the second layer material covering the outer surfaces of the first layer material.

2. A protective fabric comprising a plurality of material layers bonded together and including: a first layer formed from a plurality of adjacent strips of liquid and vapour impermeable material, each first layer strip having an inner surface and an outer surface, a portion of the inner surface along one edge of one first layer strip overlapping a portion of the outer surface of an adjacent first layer strip and establishing a gap between said overlapping portions a second layer formed from a plurality of strips of wicking material, each second layer strip covering the inner surface of a first layer strip, extending through the gap between overlapping portions of adjacent first layer strips, and covering the outer surface of the adjacent first layer strip and a third layer of liquid impermeable/vapour permeable rn/rm material extending over the second layer material covering the outer surfaces of the first layer material.

3. The protective fabric of claim 1 or claim 2 wherein the width of said gap is approximately equal to the thickness of said wicking material.

4. The protective fabric of claim 1 or claim 2 wherein the material of said first layer is a butyl rubber.

5. The protective fabric of claim 1 or claim 2 wherein the material of said first layer is a butyl rubber supported on a textile backing.

6. The protective fabric of claim 1 wherein said wicking material is selected from the group comprising woven or knitted fabrics of nylon, polyester, polypropylene, or blends thereof with cotton or nonwoven fibrous material having a paper-like structure, such fibrous material having a surface treatment to make them wettable.

7. The protective fabric of claim 6 wherein the material of said third layer is selected from the group comprising: conventional woven or nonwoven textile fabrics treated with a liquid repellent composition; liquid resistant microporous films or coatings; hydrophilic polymers; or hydrophilic polymers in conjuction with microporous liquid resistant membranes.

8. The protective fabric of claim 7 including a fourth layer of fabric material covering said third layer, the material of said fourth layer being a conventional woven or knitted fabric.

9. The protective fabric of claim 2 wherein said rn/rm 13 wicking material is selected from the group comprising woven or knitted fabrics of nylon, polyester, polypropylene, or blends thereof with cotton or nonwoven fibrous material having a paper-like structure, such fibrous material having a surface treatment to make them wettable.

10. The protective fabric of claim 9 wherein the material of said third layer is selected from the group comprising: conventional woven or nonwoven textile fabrics treated with a liquid repellent composition liquid-resistant microporous films or coatings; hydrophilic polymers or hydrophilic polymers in conjuction with microporous liquid-resistant membranes,

11. The protective fabric of claim 10 including a fourth layer of fabric material covering said third layer, the material of said fourth layer being a conventional woven or knitted fabric.

12. The protective fabric of claim 6 or claim 9 wherein said wicking material is treated with micro-encapsulated charcoal or a micro-encapsulated reactive chemical for absorbing or chemically destroying chemical agents which might penetrate said third layer and reach the wicking material of said second layer,

13. A protective suit manufactured from the protective fabric of claim 1 or claim 2, said suit being designed to have the wicking material of said second layer which covers the inner surface of said first layer in contact with the skin of a wearer of said suit.

14. A reinforcement for vulnerable areas of an rn/rm article of clothing, said reinforcement being manufactured from the protective fabric of claim 1 or claim 2 such that the wicking material of said second layer which covers the inner surface of said first layer is in contact with the skin of a wearer of said article of clothing.

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