US 3572397 A
Description (OCR text may contain errors)
' March 23,1971 I 'D. T. AUSTIN 3mm? NONCOMBUS'IION-SUPPORTING FABRIC Filed Dec. 27, 1968 'INVENTOR. Demzm Z flasiwz United States Patent 3,572,397 NONCOMBUSTION-SUPPORTING FABRIC Dennis T. Austin, Hogansville, Ga., assignor to Uniroyal, Inc., New York, N.Y. Filed Dec. 27, 1968, Ser. No. 787,368 Int. Cl. D03d 15/00 US. Cl. 139-426 9 Claims ABSTRACT OF THE DISCLOSURE A fabric which will not support combustion is woven of warp and filling threads which consist of a mixed nylon and asbestos fiber yarn wrapped about glass filaments. The asbestos fiber content of the yarn is at least 85% by weight, and the balance is a nylon fiber of a special high temperature resistant variety such as Nomex. The resulting fabric will not support combustion, even in an environment of pure oxygen at pressures greater than atmospheric.
FIELD OF THE INVENTION This invention relates generally to nonflammable fabrics, and is particularly concerned with a fabric completely safe for use in a space capsule employing a pure oxygen atmosphere.
THE PRIOR ART The need to which this invention responds is tragically clear. Some time before the filing of this patent application, three American astronauts participating in a ground test of a space capsule employing a pure oxygen atmosphere died as a result of a fire in the capsule. Apparently combustible material within the capsule was accidentally ignited, and the fire spread so rapidly in the pure oxygen atmosphere that the men did not have time to escape.
There are a number of situations in which it is desirable or essential to avoid entirely the use of materials which support combustion; these include pure oxygen or high oxygen concentration environments, and space capsules generally (even if pure oxygen is not employed). However, in many such situations it is impossible to avoid the use of textiles containing organic fibers, which oxidize. For space applications in particular, astronauts generally wear space suits which must have a degree of flexibility and durability which can be obtained only by the use of such textiles.
Numerous previous attempts have been made to develop noncombustible fabrics by using inorganic material such as glass or asbestos fiber. Fabrics made entirely of these materials are noncombustible, but they are also quite stiff, vulnerable to abrasion and fracture, and generally difiicult to manage and fabricate.
It is known that glass and asbestos fiber textiles can be made more manageable by blending them with other fibers having greater flexibility and toughness. However known materials which may be mixed with glass or asbestos fiber in this way are organic in their chemical nature and will support combustion. (The term support combustion as used herein means that such fibers, once ignited by a heat source, continue to burn even after withdrawal of the heat source.) Previously known textile materials containing a sufficiently high percentage of organic fiber to make the end product flexible, durable and manageable, have also supported combustion, at least in a pure oxygen environment.
SUMMARY AND OBJECTS OF THE INVENTION A principal object of this invention is to provide a fabric which is flexible, durable and manageable, but
3,572,397 Patented Mar. 23, 1971 will not support combustion. Another object is to provide a fabric which is safe even in an environment of pure oxygen. A further object is to provide a nonflammable fabric which is relatively light in weight. A still further object is to provide a nonflammable fabric which has relatively high strength.
In accordance with the invention, a yarn formed of at least 85 asbestos fiber by weight, the balance being a special high temperature organic fiber, is twisted with glass filaments to form warp and filling threads which are woven into a noncombustion-supporting fabric.
BRIEF DESCRIPTION OF THE DRAWINGS The single figure of the drawing illustrates a woven fabric in accordance with this invention, and includes an enlarged insert illustrating the construction of a single thread of the fabric.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT For a number of years there has been available on the market a special variety of nylon fiber which has particularly good resistance to high temperatures. This material is sold under the brand name Nomex by the E. I. du Pont de Nemours Company, and is believed to be formed by the copolymerization of meta-phenylenediamine and isophthaloyl chloride. The manufacturer claims outstanding high temperature resistance for Nomex, in that it does not melt and has extremely low flammability. It is said that the material does not oxidize at all until a temperature of 700 F. is reached, at which point it degrades to a friable char at a rate proportional to the intensity of the heat source. In an air environment, it is known to be self-extinguishing when the material it withdrawn from the source of heat. In this patent application and the appended claims, materials of this type are referred to generically as high temperature resistant materials.
The high temperature properties of Nomex nylon fiber have been Well known in the textile industry for years, and Nomex fabrics have long been chosen for their flame resistant qualities; yet the prior art has not found a way to use this material to solve the life-and-death problem of the pure oxygen environment.
Possibly, investigators in the textile field did not expect any disproportionate results from a blend or Nomex with inorganic fibers. It may have been assumed, quite logically, that such a blend would be similar in flame resistance to a conventional blend of asbestos or glass with any other organic fibers, the Nomex blend giving less support to combustion, but only in proportion to the greater flame resistance of Nomex as compared to the other organic fiber.
The present invention is based upon the unexpected discovery that any such parallel between the flame resistance of Nomex blends and blends of other organic fibers terminates abruptly at a critical threshold level of composition. Actual tests conducted at the facilities of the National Aeronautics and Space Administration have shown that textiles comprising a yarn blended of asbestos and Nomex fibers Will support combustion, at least in a pure oxygen environment, even though the asbestos content of the yarn is as high as by weight. Under such conditions, at a pressure of only one atmosphere absolute, combustion rates of .017 inch in warp and .01218 inch in filling were observed. But when the proportion of asbestos to Nomex fiber in the yarn was raised to the critical level of the material refused entirely to support combustion even in an environment of pure oxygen at pressures up to at least two atmospheres absolute, extinguishing itself spontaneously when it was withdrawn from the heat source. The fabric of this invention is therefore the first textile material known to applicant which has the flexibility characteristic of textiles comprising organic fibers, yet will not support combustion even in a pure oxygen environment.
Turning our attention to the single figure of the drawing, the fabric of this invention comprises a plurality of warp threads 12 and filling threads 14 which are woven together in the conventional manner. In a particular embodiment which was actually used in the flame resistance tests mentioned above, the thread count was twenty-four per inch in warp by twenty per inch in filling.
The detailed structure of a particular warp thread 12, which is identical to that of all the threads 12 and 14, is schematically illustrated in the enlarged insert. A large proportion of asbestos fibers and a smaller proportion of Nomex fibers have been blended to form a composite cover strand 20 which is wrapped upon a glass multifilament strand 22 to form the thread 12. A similar enlarged view of any other thread 12 or 14 would show an identical micro-structure. In accordance with this invention, the proportion of asbestos fiber in the cover strand or wrapping 20 should be not less than 85% by weight and the proportion of Nomex fibers therein not greater than 15% by weight. The preferred wrapping composition is 92% by weight of asbestos fiber and 8% by weight of Nomex fiber. The preferred material for the glass filaments 22 is Beta 'Fiberglas, which minimizes the tendency of glass fiber materials to irritate the skin of the wearer.
The asbestos and Nomex fibers are blended into the strand in the conventional manner, this being illustrated schematically in the drawing since the equipment and techniques for accomplishing this are quite well known in the industry. The preferred size of strand 20 is cut, and the preferred size of the Fiberglas multifilament strand 22 is 150-1/0. After a 25 cut cover strand 20 has been wrapped on a 150-1/0 core strand 22, the size of the resulting composite thread 12 or 14 is 19 cut. The threads 12 and 14 so formed are woven in the usual manner to form the fabric 10, which is then water brushed and given a standard finishing.
When the preferred cover composition of 92% asbestos to 8% Nomex is employed with the preferred Beta Fiberglas material, the resulting overall fabric composition is 79% by weight of asbestos fiber, 7% by weight of Nomex fiber, and 14% by weight of Fiberglas filaments.
The fabric 10 has relatively high strength and light weight, in addition to its flame resistant properties. The tear strength was measured at 16 pounds in warp and 17 pounds in filling. The tensile strength was measured at 81 pounds in warp and 67 pounds in filling. Yet despite this strength the fabric has a weight of only 13 ounces per square yard. As a result, space suits and other garments formed of the fabric 10 are relatively light in Weight and therefore less of an encumbrance to the astronauts wearing them. But they are also strong, flexible, and abrasion resistant, and are not easily damaged by tear or tensile stress.
However, the key property, of course, is the fact that in the event of a momentary electrical mishap, even if the fabric 10 of the space suit is briefly ignited, it will immediately cease to turn as soon as the electrical fault situation is terminated, as for example by the blowing of a protective fuse. When this happens, the electrical source of heat is effectively removed, and the fabric 10 of the spacesuit will burn no longer. This fact can easily make 4 the difference between life and death for the astronauts who are in the space capsule at the time that the mishap occurs. It is important to note that this degree of safety is achieved even in a pure oxygen environment, and even if the ambient pressure is higher'than atmospheric.
Since the foregoing description and drawings are merely illustrative, the scope of protection of the invention has been more broadly stated in the following claims, and these should be liberally interpreted so as to obtain the benefit of all equivalents to which the invention is fairly entitled.
The invention claimed is:
1. A noncombustion-supporting fabric comprising an asbestos fiber, an organic nylon fiber which is self-extinguishing when withdrawn from a heat source, said nylon fiber being formed from the copolymerization of metaphenylenediamine and isophthaloyl chloride, said asbestos fiber being at least by weight of the combined weights of said asbestos fiber and said organic fiber, and essentially no other organic material.
2. A fabric as in claim 1 consisting essentially of 79% by weight of said asbestos fiber, 7% by weight of said organic fiber, and 14% by weight of additional inorganic material.
3. A fabric as in claim 1 wherein the percentage by weight of said asbestos fiber to said combined weights is substantially 92% 4. A fabric as in claim 2 wherein said additional inorganic material is glass.
5. A noncombustion-supporting fabric woven of warp and filling threads, said threads consisting essentially of a strand wrapped about an inorganic filament, said strand consisting essentially of (a) at least 85% by weight of asbestos fiber, and
(b) the balance an organic nylon fiber which is self extinguishing when withdrawn from a heat source, said nylon fiber being formed from the copolymerization of meta-phenylenediamine and isophthaloyl chloride, said fabric containing essentially no other organic material.
6. A fabric as in claim 5 wherein said organic fiber consists of a high temperature resistant variety of nylon.
7. A fabric as in claim 6 wherein said inorganic filament consists essentially of glass.
8. A fabric as in claim 7 wherein the proportion of asbestos fiber in said strand is substantially 92%.
9. A fabric as in claim 8 consisting essentially of 79% by weight of said asbestos fiber, 7% by weight of said high temperature resistant nylon fiber, and 14% by weight of said glass filament.
References Cited UNITED STATES PATENTS 2,132,702 10/1938 Simpson 139-420X 2,133,237 10/1938 Slayter 139-42OX 2,217,049 10/1940 Greenleaf 57-144 2,503,237 4/1950 Palm et al. 57l44- 3,090,103 5/1963 Crawley 139420X 3,366,001 l/1968 Meserole 57144X FOR'EIGN REFERENCES 1,017,618 9/1952 France 139426 JAMES KEE CHI, Primary Examiner U.S. Cl. X.R. 57-140