FLEXIBLE HEAT BARRIER AND FIRE SHELTER FOR WILDLAND FIREFIGHTERS MADE THEREFROM

Abstract

A flexible heat barrier is configured to absorb and deflect heat energy and utilizes a multilayer construction wherein each layer provides a specific purpose. An outer layer configured for exposure to a heat flux includes a coating having an intumescent component and an opacifier component. An inner layer includes a foil that may include a high emittance coating to more effectively reflect radiation. A middle layer includes an insulating fabric layer that may include oriented fibers that can effectively polarize radiation and may include a plurality of layers of oriented fibers that are configured at an offset angle to deflect and reduce radiation transmission through the middle layer. A flexible heat barrier may also include a flexible gas barrier that includes a phase change material, such as frits that melt at a predetermined temperature and flow into gaps to reduce the permeability and further block heat flux.

Claims

1. A flexible heat barrier comprising: a) an insulating fabric layer comprising high temperature fibers having a melt temperature of at least 800° C.; b) a coating coupled to said insulating fabric layer and configured as an outer layer of the flexible heat barrier and comprising: i) an intumescent component; ii) an opacifier component; iii) a gas barrier component; and iv) a binder component; c) a metal foil coupled to said insulating fabric layer and configured as an inner layer of the flexible heat barrier; wherein the outer layer is configured as an exposure side of the flexible heat barrier and configured to be exposed to a heat source or a flame and the inner layer is configured as a shield side away from said heat source or flame; and wherein the flexible heat barrier has an average burst strength of at least 482 kPa (70 psi) according to American Standard Test Method (ASTM) 774 and United States Department of Agriculture (USDA) specification paragraph 4.4.2.7.

2. The flexible heat barrier of claim 1, wherein the insulating fabric layer is a polarizing fabric layer comprising a layer or oriented high temperature fibers having a spacing between said oriented fibers of 5.0 .Math.m or less.

3. The flexible heat barrier of claim 2, wherein the spacing between said oriented fibers is 2.0 .Math.m or less.

4. The flexible heat barrier of claim 2 wherein the oriented fibers comprise a coating and wherein the coating forms said spacing between the oriented fibers.

5. The flexible heat barrier of claim 1, wherein the insulating fabric layer comprises two layers of oriented high temperature fibers, each having a spacing between said oriented fibers of 5.0 .Math.m or less.

6. The flexible heat barrier of claim 5, wherein a first layer of oriented high temperature fibers is configured substantially orthogonally, within about 20 degrees or less of orthogonal, to a second layer of oriented high temperature fiber.

7. The flexible heat barrier of claim 5, wherein the second layer of oriented high temperature fibers is configured more proximal to the inner layer and has a larger spacing between said oriented fibers by at least 20% than said spacing between said oriented fibers of the first layer of said oriented fibers.

8. The flexible heat barrier of claim 7, wherein the second layer of oriented high temperature fibers has a larger fiber diameter, by at least 20%, than a fiber diameter of the first layer of said oriented fibers.

9. The flexible heat barrier of claim 5, wherein the second layer of oriented high temperature fibers has a larger fiber diameter, by at least 20%, than a fiber diameter of the first layer of said oriented fibers.

10. The flexible heat barrier of claim 2, wherein the insulating fabric layer comprises woven oriented fibers.

11. The flexible heat barrier of claim 1, wherein insulating fabric layer comprises high temperature polymers having a melt temperature of 300° C. or more.

12. The flexible heat barrier of claim 11, wherein insulating fabric layer comprises polyimide.

13. The flexible heat barrier of claim 1, wherein insulating fabric layer comprises fibers having a melt temperature of 800° C. or more.

14. The flexible heat barrier of claim 1, wherein insulating fabric layer comprises inorganic fibers selected from the group consisting of: glass, fiberglass, silicon carbide and mullite, alumina, quartz.

15. The flexible heat barrier of claim 1, wherein the foil comprises a first layer of foil and second layer of foil, wherein the first layer of foil has an emissivity that is at least 20% higher than an emissivity of said second layer of foil.

16. The flexible heat barrier of claim 1, wherein the foil comprises gold layer.

17. The flexible heat barrier of claim 16, wherein the gold layer is a vapor deposition gold layer having thickness of no more than about 1500 .Math.m.

18. The flexible heat barrier of claim 16, wherein the foil comprises titanium foil.

19. The flexible heat barrier of claim 18, wherein the foil comprises a gold layer on said titanium foil.

20. The flexible heat barrier of claim 1, wherein the intumescent component comprises expandable graphite.

Description

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0044] The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention.

[0045] FIG. 1 shows a perspective top view of a fire shelter.

[0046] FIG. 2 shows several prototype fire shelters evaluated during development of the M2002

[0047] FIG. 3 shows a graph of Temperature And Heat Flux Comparison, With And Without FGB.

[0048] FIG. 4 shows a diagram of the layers of an exemplary fire shelter, lay-up #2, compared with two other lay-ups, including the M2002 fire shelter and another experimental lay-up, Lay-up #1.

[0049] FIG. 5 shows the Meker Burner test results for duration for the fire shelter lay-ups depicted in FIG. 4.

[0050] FIG. 6 shows a graph of Meker burner results for two fire shelter lay-ups containing an FGB that offer significantly improved habitability compared to the M2002, for which data is also plotted.

[0051] FIG. 7 shows a cross-sectional diagraph of an exemplary middle layer having a fabric configured between and integrally coupled to a coating on the hot side, and a foil on the cold side.

[0052] FIG. 8 shows a prospective view of an exemplary insulating fabric layer having layers of oriented fibers configured orthogonally to each other.

[0053] FIG. 9 shows the results of Meker burner tests for three-layer fire shelter systems including a middle layer as depicted in FIG. 8 with the construction as described herein.

[0054] FIG. 10 shows photographs of the shield side of the flexible heat barrier following a Meker burner test.

[0055] FIG. 11 shows photographs of the exposure side of the flexible heat barrier following a Meker burner test.

[0056] FIG. 12 shows a graph of emittance values for foil over wavelength of interest for a fire shelter application.

[0057] FIG. 13 shows a graphical model of radiant heat transfer through a polarizing fiber array.

[0058] FIG. 14, FIG. 15 and FIG. 16 show a graphical model of the effect of a polarizing fiber array with varying gap distances between the oriented fibers.

[0059] FIG. 17 shows a chart of transmittance, reflectance and absorption through a polarizing fiber array.

[0060] FIG. 18 shows a diagram of a woven fabric that may be a layer or component of the insulating fabric layer

[0061] Corresponding reference characters indicate corresponding parts throughout the several views of the figures. The figures represent an illustration of some of the embodiments of the present invention and are not to be construed as limiting the scope of the invention in any manner. Some of the figures may not show all of the features and components of the invention for ease of illustration, but it is to be understood that where possible, features and components from one figure may be an included in the other figures. Further, the figures are not necessarily to scale, some features may be exaggerated to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0062] As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Also, use of “a” or “an” are employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

[0063] Certain exemplary embodiments of the present invention are described herein and are illustrated in the accompanying figures. The embodiments described are only for purposes of illustrating the present invention and should not be interpreted as limiting the scope of the invention. Other embodiments of the invention, and certain modifications, combinations and improvements of the described embodiments, will occur to those skilled in the art and all such alternate embodiments, combinations, modifications, improvements are within the scope of the present invention.

[0064] Referring now to FIGS. 1 and 2, a fire shelter forms a top shielding surface or enclosure and is configured to fit into a compact space, such as a backpack. The fire shelter is configured to be folded and configured in the backpack. The image of the backpack is not to scale. As shown in FIG. 2 a plurality of fire shelters can be deployed to form a protective dome over each firefighter in a group.

[0065] As shown in FIG. 3 instantaneous heat flux in forced convection environment can be greatly reduced by the addition of a Flexible Gas Barrier (FGB) layer. FIG. 3 compares instantaneous heat flux, Qinstant and temperatures in two locations over a 60 second exposure for insulation systems with and without the FGB. The system with the FGB indicates significantly lower heat flux resulting in significantly lower temperatures at both locations measured.

[0066] A flexible gas barrier (FGB #28), a ceramic paper with a phase change material including frits and vermiculite, was developed for use as the middle layer in a fire shelter lay-up shown in FIG. 4. flexible heat barrier

[0067] The weights and thicknesses of the materials in the three constructions of FIG. 4 as well as a Phase 1 target are tabulated in Table 5.

TABLE-US-00005 M2002 Lay-up #1 Lay-up #2 FGB#28 Phase 1 Target Outer g/m2 434 301.8 301.8 301.8 Middle g/m2 n.a. n.a. 115.3 186.5 Inner g/m2 94.9 94.9 94.9 94.9 Total Shelter Wall g/m2 528.9 396.7 512 583.2 Floor kg 0.531 0.390 0.390 0.390 Seams kg 0.086 0.086 0.086 0.086 Complete Shelter, kg 1.99 1.51 1.81 1.99 Wall Thickness, mm 0.762 0.584 0.914 0.991

[0068] Also, the thermal performance of these constructions was tested and plotted in FIG. 5, where the intersection of the calorimeter temperature data with the Stoll curve predicts the fire shelter failure due to second degree burns on the occupant. As shown from the weights in Table 5 and the Meker burner test results in FIG. 5, increasing wall weight improves performance and delays second degree burns. It can also be seen that the performance of the M2002 was matched by lay-up #2, which is 10% lighter than the M2002. The Flexible Gas Barrier (FGB #28) layer was used as the MIDDLE layer in lay-up #2, and provided equivalent performance to the M2002 construction at a lighter weight.

[0069] As shown from the weights of the components in Table 5 and the Meker burner test results in FIG. 5, increasing weight improves performance and delays second degree burns. It can also be seen that the performance of the M2002 was matched by lay-up #2, which is 10% lighter than the M2002. This suggests that an insulating fabric layer that is slightly heavier than FGB #28 can be successfully utilized to increase fire shelter habitability by 20% without increasing overall weight or bulk. In these tests, a Flexible Gas Barrier (FGB) layer was configured between fabric laminates similar to those currently used in the M2002.

[0070] The insulating fabric layer may be specifically optimized to increase time to second degree burn, or shelter protection time. In an exemplary embodiment, an improvement of about 20% (~11 second) over M2002 is realized with no increase in weight or bulk over M2002. This improvement will produce a fire shelter with improved efficacy resulting in fewer injuries and deaths for firefighters and support personnel. The cost of an exemplary fire shelter of the present invention may be maintained to a marginal amount over the cost of the M2022 fire shelter, such as no more than about $100 per shelter, or even no more than $85 per shelter.

[0071] As shown in FIG. 6, research and development further confirmed that a FGB layer that meets the weight and thickness constraints of the proposed fire shelter design and also increased survivability by 20%. The Meker burner test data confirms that the M2002 is survivable for 54 seconds in the controlled test, and the flexible heat barrier with the FGB configured between the coating and the foil layer increases survivability to 64 seconds, representing a 20% improvement. FGB - #1 and FGB - #2 are plots of data from two separate runs of the same FGB material, meant to indicate the repeatability of the results. Of course, full shelters would need to be constructed and tested to confirm the suitability of other aspects of the design.

[0072] An exemplary fire shelter of the present invention meets the following qualifications: [0073] a. Maintain radiant heat protection of the current M2002 fire shelter [0074] b. Improve protection in direct flame contact [0075] c. Maintain the requirement that users not be exposed to dangerous toxic compounds from the shelter [0076] d. Maintain the strength and durability of the current M2002 fire shelter [0077] e. Prevent flammable gasses from collecting inside the fire shelter [0078] f. Maintain the weight and bulk of the current M2002 fire shelter [0079] g. Marginal to no increase in cost over the M2002 fire shelter.

[0080] As shown in FIG. 7, an exemplary flexible heat barrier 30 comprises an insulating fabric layer 60 with a coating 40 configured on an exposure side 24, and a metal foil 80 configured on a shield side 26. Could be 90 except we use that later. As described herein the coating 40 is configured to reduce heat transmittance, while the insulating layer is configured to provide structural support and insulate the shield side from heat and the metal foil is configured to reduce heat radiated from the cold side and provide a gas barrier.

[0081] As described herein, the insulating fabric layer may comprise two or more layers of high-temperature, oriented fibers. The layers may have the oriented fibers oriented orthogonally to each other, or within about 20 degrees of orthogonal to polarize the radiant energy. A thin layer of optically transparent material, like a nonwoven alumina mat, or woven quartz scrim may be used to thermally isolate the layers of oriented fibers without significantly interfering with the polarization process. An adhesive 50 may be used to bond the metal foil layer to the insulating fabric layer. The coating layer 40 may include a binder 45 that adheres the coating to the insulating fabric layer. Table 2 shows the construction of an exemplary flexible heat barrier shown in FIG. 7.

[0082] The coating 40 includes an intumescent component 42, a gas barrier component 44, such as vermiculite and an opacifier component 46 held together by the binder 45. The ratio of these components may be selected as described herein to provide effective heat shielding properties and survival time.

[0083] A flexible gas barrier (FGB) 90 is configured with the flexible heat barrier 30 and contains a gas barrier 44′, such as vermiculite 94 and pyrometric particles 91 comprising frits 92, fluxes 93 that are configured to melt at prescribed temperature to flow and fill spaces between the gas barrier material. As described herein, the FGB may be a coating configured with one or more of the layers of the flexible heat barrier or may be a separate layer configured on or between the fibers of the layers, such as between the coating 40 and insulating fabric layer 60 or between the insulating fabric layer and the foil 80.

[0084] As shown in FIG. 8, an exemplary insulating fabric layer 60 includes a first layer 66 of fibers 62 that are oriented fibers 64 and a second layer 68 with oriented fibers that are configured orthogonally to the oriented fibers in the first layer. As described herein, this arrangement of oriented fibers with a very small fiber gap may effectively polarize radiant energy to better insulate the shield side of the flexible heat barrier. As described herein, the fibers may be small in diameter, and the gaps between the parallel or oriented fibers may be substantially the same as the wavelength of the peak radiant energy.

[0085] FIG. 9 shows the results of a Meker burner test for three three-layer fire shelter systems with weights and thickness predicted in Table 5 for the Phase I target, and better performance than anticipated in FIG. 5 for the Phase I target. The Meker Burner test shows the intersection of the calorimeter temperature data with a Stoll curve and therefore predicts the fire shelter failure due to 2.sup.nd degree burns on the occupant. This lay-up includes the flexible heat barrier described in Table 2 used in place of FGB #28 in the configuration shown for lay-up #2 in FIG. 4. FIG. 9 shows that each of the flexible heat barriers tested had a survival time of 86 seconds. The flexible heat barrier middle layer increases survivability to 86 seconds in the Meker burner test, which represents a 59% improvement over the M2002. The construction of the present flexible heat barrier for a fire shelter application is expected to be more commercially viable than the technology described in U.S. Pat. No. 10,099,450 because the vermiculite dispersion is not relied upon for adhering the foil to the insulating fabric layer. Lastly, the distinct layers of the flexible heat barrier each provide a unique benefit, wherein the insulating fabric layer provides added strength, the foil provides a low emittance and the coating absorbs heat while the intumescent component expands with exposure to heat.

[0086] FIGS. 10 and 11 show the fire shelter layers after Meker Burner testing. The exposure side 24 was exposed to the burner during this testing. FIG. 10 shows the shield side of a flexible heat barrier, the side that would be exposed to the fire fighter in a fire shelter application. As can be seen, it’s in good condition even after providing 86 seconds of protection. In FIG. 11, the exposure side shows delamination, as is typical with severe exposures such as this. Also, the intumescent component 42 has intumesced on the exposure side. Since the test only exposes a circular section in the middle of the 15.24 cm square samples, unexposed material, as it would appear in an unused fire shelter, may be seen outside of the central area.

[0087] FIG. 12 shows a graph of emittance values for foil over wavelength of interest for a fire shelter application.

[0088] Referring now to FIGS. 13 to 17, an insulating fabric layer 60 with a polarizing array of fibers 62, can effectively polarize radiant energy. As shown in FIG. 13, oriented fibers 64 with diameters 63 and a gap distance 65 between the fibers may be sized with gaps that approach the wavelength 67 of the radiant energy. When the gap distance is the same or smaller than the wavelength of the radiant energy, the radiant energy will be polarized as it passes through the oriented fibers 64. As shown in FIG. 14 to FIG. 16, the diameter of the fibers and again the gap distance between them will affect the polarization of the light. A gap distance greater than, equal to and smaller than the wavelength of radiation (1 micron) are modeled. Diagram 14 represents a fiber diameter of 0.6 microns and a gap distance of 2.0 microns, greater than the wavelength of the radiation. Diagram 15 represents a fiber diameter of 0.6 microns and a gap distance of 1.0 microns, equal to the wavelength of the radiation. Diagram 16 represents a fiber diameter of 0.6 microns and a gap distance of 0.5 microns, smaller than the wavelength of the radiation. FIG. 17 shows the percent vertical polarization along a line parallel to the fiber-line on the transmitted side of the fibers. The results shows that the fibers do polarize the unpolarized incident radiation. Polarization of the radiation occurs to a greater extend when the gap distance is equal to or smaller than the wavelength of radiation. Polarization of the radiation up to 40 to 50% was predicted for the smallest gap distance spacing of 0.5 um.

[0089] As shown in FIG. 18, a woven fabric 67 may be a layer or component of the insulating fabric layer 60 and may include a first set of oriented fibers 64, and a second set of oriented fibers 64′. The first set of oriented fibers 64 in the weave may be a different type of fiber from the second set of oriented fibers 64′. The woven fabric includes fibers 62 that may be selected from high temperature fibers as described herein, such as polarizing silicon carbide fibers, quartz fibers, glass fibers and the like. The warp fibers may be one type of fiber while the fill fibers or yarns may be a second type of fiber. The fibers may also include opacifier powders, fibers and/or frits that are powders or fibers and configured to melt and flow to seal off gaps in the weave. The weave may be a plain or basket weave, twill weave, satin weave, or leno weave. A frit fiber may be only a portion of the yarn or strand in the weave. In an exemplary embodiment a first set of fibers or yarns, the warp yarns, comprise polarizing silicon carbide fibers and a second set of fibers or yarns, the weft yarns, comprise optically transparent quartz fibers in a plain, satin, basket, twill or leno weave. The weave and the denier of the weft fibers may be selected to maintain the desired spacing between the polarizing fibers, such as silicon carbide fibers.

[0090] A coating 78 may be configured on and/or around the fibers to create the spacing between the fibers. The spacing may be the thickness of the coating between the fibers or the combined thickness of a coating on adjacent fibers. The coating may be continuous around the fibers forming a continuous layer or discontinuous.

[0091] It will be apparent to those skilled in the art that various modifications, combinations and variations can be made in the present invention without departing from the scope of the invention. Specific embodiments, features and elements described herein may be modified, and/or combined in any suitable manner. Thus, it is intended that the present invention cover the modifications, combinations and variations of this invention provided they come within the scope of the appended claims and their equivalents.