Patent Publication Number: US-2021189611-A1

Title: Flame resistant fabrics with increased strength

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/950,193, filed Dec. 19, 2019, the entirety of which is hereby incorporated by reference. 
    
    
     FIELD 
     Embodiments of the present invention are directed to flame resistant fabrics formed of a plurality of spun body yarns and rip stops that extend between at least some of the spun body yarns in at least one of the warp or fill direction of the fabric. In some embodiments, the rip stops include at least two relatively tough yarns, and the relatively tough yarns include a core and a sheath. 
     BACKGROUND 
     Protective garments are designed to protect the wearer from hazardous environmental conditions the wearer might encounter. Such garments include those designed to be worn by firefighters and other rescue personnel, industrial and electrical workers, and military personnel. 
     High tenacity, flame resistant fabrics have been developed for military and other applications. Examples of such fabrics are disclosed in U.S. Pat. No. RE42,309, the entirety of which is herein incorporated by this reference. One particular fabric of the market today (sold under the tradename Defender® M Ripstop) is a plain weave fabric formed with spun body yarns having a blend of flame resistant rayon, para-aramid, and nylon fibers (specifically 65% flame resistant rayon/25% para-aramid/10% nylon). Of particular concern in the design of fabrics for military applications is fabric durability as defined by tensile (i.e. breaking) strength and tear strength. Rip stop yarns have been incorporated into these woven fabrics to enhance the strength of such fabrics. For example, the Defender® M Ripstop fabric includes rip stops formed by two body yarns. More specifically, the two body yarns are woven as one in both the warp and fill directions at specified intervals. In this way, the fabric is formed entirely of the same yarns but constructed in a way to impart strength to the fabric. 
     However, the high concentration of rayon fibers in the fabric can detrimentally impact the strength of the fabric. More specifically, rayon fibers weaken when exposed to water and moisture. Thus, the body yarns serving the rip stop function are less able to impart strength to the fabric after such exposure. Thus, there is a need for a fabric that is better able to retain its strength properties after exposure to water and moisture all the while remaining flame resistant and cost-effective. 
     SUMMARY 
     The terms “invention,” “the invention,” “this invention” and “the present invention” used in this patent are intended to refer broadly to all of the subject matter of this patent and the patent claims below. Statements containing these terms should not be understood to limit the subject matter described herein or to limit the meaning or scope of the patent claims below. Embodiments of the invention covered by this patent are defined by the claims below, not this summary. This summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to the entire specification of this patent, all drawings and each claim. 
     In some embodiments, the flame resistant fabric has a warp direction and a fill direction. The flame resistant fabric includes a plurality of spun body yarns each formed of a body yarn fiber blend and provided in both the warp direction and the fill direction of the fabric. The fabric can also include a plurality of rip stops extending between at least some of the spun body yarns in at least one of the warp direction or the fill direction of the fabric. In some embodiments, each rip stop includes at least two relatively tough yarns and each relatively tough yarn includes a core and a sheath. In some embodiments, the core includes an 100% aramid spun yarn and the sheath includes a sheath fiber blend. 
     In some embodiments, the flame resistant fabric has a warp direction and a fill direction. The flame resistant fabric includes a plurality of spun body yarns each formed of a body yarn fiber blend and provided in both the warp direction and the fill direction of the fabric, where in some embodiments the body yarn fiber blend includes 50-80% FR rayon fibers, 15-40% aramid fibers, and 5-20% nylon fibers. The fabric can also include a plurality of rip stops extending between at least some of the spun body yarns in at least one of the warp direction or the fill direction of the fabric. In some embodiments, each rip stop includes at least two relatively tough yarns formed of a core and a sheath. In some embodiments, the core includes an 100% aramid spun yarn and the sheath includes a sheath fiber blend including 50-80% FR rayon fibers, 15-40% aramid fibers, and 5-20% nylon fibers. In some embodiments, five to twenty-five body yarns are interposed between adjacent rip stops in the at least one of the warp direction or the fill direction. 
     In some embodiments, the flame resistant fabric has a warp direction and a fill direction and includes a plurality of spun body yarns provided in both the warp direction and the fill direction of the fabric. In some embodiments, the spun body yarns are formed of a body yarn fiber blend that includes 50-80% FR rayon fibers, 15-40% para-aramid fibers, and 5-20% nylon fibers. The fabric can also include a plurality of rip stops extending between at least some of the spun body yarns in both the warp direction and the fill direction of the fabric. In some embodiments, at least some of the plurality of rip stops are formed of two relatively tough yarns that include a core and a sheath. In some embodiments, the core includes an 100% para-aramid spun yarn and the sheath includes a sheath fiber blend including 50-80% FR rayon fibers, 15-40% para-aramid fibers, and 5-20% nylon fibers. In some embodiments, the body yarn fiber blend and the sheath fiber blend are substantially identical, ten to twenty body yarns are interposed between adjacent rip stops in the warp direction and the fill direction of the fabric, and the fabric has a weight between 5-7 ounces per square yard, inclusive. 
    
    
     DETAILED DESCRIPTION 
     The subject matter of embodiments of the present invention is described here with specificity to meet statutory requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described. 
     Disclosed are flame resistant fabrics formed with a plurality of flame resistant body yarns that form a body of the fabric and a plurality of relatively tough yarns provided in discrete positions within the fabric body to help impart strength to the fabric. Embodiments of the present invention replace the rip stop body yarns with a different yarn that is less apt to degrade or weaken when exposed to water and moisture and thus able to continue to impart the necessary strength after such exposure. 
     Embodiments of the fabrics disclosed herein are flame resistant in compliance with GL-PD-07-12, Rev. 9 ( Purchase Description: Cloth, Flame Resistant,  2016, incorporated herein by reference) and MIL-PRF-32635:  Cloth, Flame Resistant  (2019, incorporated herein by reference), both of which require that the fabric pass a number of different performance tests, including compliance with the thermal protective requirements of having a 4 inch (or less) char length and a 2 second (or less) afterflame when measured pursuant the testing methodology set forth in ASTM D6413— Standard Test Method for Flame Resistance of Textiles  ( Vertical Test ) (2015 edition, the entirety of which is hereby incorporated by reference). 
     To test for char length and afterflame, a fabric specimen is suspended vertically over a flame for twelve seconds. The fabric must self-extinguish within two seconds (i.e., it must have a 2 second or less afterflame). After the fabric self-extinguishes, a specified amount of weight is attached to the fabric and the fabric lifted so that the weight is suspended from the fabric. The fabric will typically tear along the charred portion of the fabric. The length of the tear (i.e., the char length) must be 4 inches or less when the test is performed in both the machine/warp and cross-machine/weft directions of the fabric. A fabric sample is typically tested for compliance both before it has been washed (and thus when the fabric still contains residual—and often flammable—chemicals from finishing processes) and after a certain number of launderings. 
     The body yarns comprise spun yarns that are constructed of flame resistant material(s). In some embodiments, the body yarns are formed with inherently FR staple fibers or staple fibers that have been treated to be flame resistant. Exemplary FR and non-FR materials useful for forming the body yarns of the invention include, but are not limited to, aramids (including para-aramid and meta-aramid); polybenzimidazole (“PBI”); polybenzoxazole (“PBO”); modacrylic; poly{2,6-diimidazo[4,5-b:40;50-e]-pyridinylene-1,4(2,5-dihydroxy)phenylene} (“PIPD”); ultra-high molecular weight (“UHMW”) polyethylene; UHMW polypropylene; polyvinyl alcohol; polyacrylonitrile; liquid crystal polymer; glass; nylon; carbon; silk; polyamide; polyester; and natural and synthetic cellulosics (e.g., cotton, rayon, acetate, triacetate, and lyocell fibers, as well as their flame resistant counterparts FR cotton, FR rayon, FR acetate, FR triacetate, and FR lyocell), TANLON™ fibers (available from Shanghai Tanlon Fiber Company), wool, melamine (such as BASOFIL™, available from Basofil Fibers), polyetherimide, polyethersulfone, pre-oxidized acrylic, polyamide-imide fibers such as KERMEL™ polytetrafluoroethylene, polyvinyl chloride, polyetheretherketone, polyetherimide fibers, polychlal, polyimide, polyimideamide, polyolefin, polyacrylate, and any combination or blend thereof. 
     Examples of para-aramid materials include KEVLAR™ (available from DuPont), TECHNORA™ (available from Teijin Twaron BV of Arnheim, Netherlands), and TWARON (also available from Teijin Twaron BV). Examples of meta-aramid materials include NOMEX™ (available from DuPont), CONEX™ (available from Teijin), and Kermel (available from Kermel). An example of a suitable modacrylic material is PROTEX™ available from Kaneka Corporation of Osaka, Japan. An example of a PIPD material includes M5 (Dupont). Examples of UHMW polyethylene materials include polymer material is VECTRAWM (available from Kuraray). Examples of suitable rayon materials are Viscose™ and Moda™ by Lenzing, available from Lenzing Fibers Corporation. An example of an FR rayon material is Lenzing FR™, also available from Lenzing Fibers Corporation. Examples of lyocell material include TENCEL G 100™ and TENCEL AlOO™, both available from Lenzing Fibers Corporation. 
     In some embodiments, the body yarns are a blend of at least rayon, aramid, and nylon fibers, such as 50-80% FR rayon fibers, 15-40% aramid fibers (e.g., para-aramid fibers), and 5-20% nylon fibers. In some embodiments, the body yarns have the same blend as the body yarns in the Defender® M Ripstop fabric (specifically 65% FR rayon/25% para-aramid/10% nylon). In other embodiments, the body yarns have a blend of 70% FR rayon, 20% para-aramid, and 10% nylon. Other fibers could be included in the body yarns. Each end of the body yarns may be formed of a single body yarn or multiple body yarns may be plied or otherwise combined to form an end. 
     In addition to the body yarns, relatively tough yarns are provided in discrete rip stop locations within the fabric. As is known in the art, “toughness” is a property that pertains to a material&#39;s (in this case a yarn&#39;s) ability to resist breakage. The term “relatively tough” is used herein to describe yarns that have higher toughness than the remainder of the yarns (i.e., body yarns) of the fabric. 
     The relatively tough yarns can be any type of yarn, including, but not limited to, spun, filament, stretch broken, and corespun yarns. In some embodiments, the relatively tough yarns are devoid of filament yarns. Materials useful in the relatively tough yarns include, but are not limited to, the same fibers identified above for use in the body yarns. The relatively tough yarns can include any combination of FR/non-FR materials, as long as the overall fabric is flame resistant and/or satisfies the applicable or desired standards for flame resistant fabrics (e.g., GL-PD-07-12, Rev. 9). Each end of the relatively tough yarns may be formed of a single yarn or multiple yarns may be combined, coupled, or covered (i.e., plied, ply twist, wrapped, coresheath, coverspun, etc.) to form an end. 
     In some embodiments, the relatively tough yarns include aramid (e.g., para-aramid) content to impart the necessary strength to the fabric. For example, in one embodiment the relatively tough yarns include a 100% aramid (e.g., para-aramid) spun yarn. While the 100% aramid spun yarn may alone form the relatively tough yarn, in other embodiments it is plied with another yarn to form a relatively tough yarn. For example, in one embodiment a 100% aramid spun yarn is plied with a body yarn to form a relatively touch yarn. 
     In still another embodiment, the relatively tough yarns are spun yarns having a blend of flame resistant staple fibers, such as those disclosed above. In a more specific embodiment, the relatively tough yarns are spun yarns formed of a blend of aramid and FR rayon fibers (e.g., 50/50 blend). 
     In still another embodiment, the relatively tough yarns are corespun yarns having a core yarn about which a plurality of individual staple fibers are spun to form a fiber sheath that surrounds the core yarn. By way of example, the staple fibers can be spun around the core yarn using a dref spin procedure or air jet spinning process. The core yarn and staple fibers can be one or more of the various materials identified above. In one embodiment, the core yarn is a 100% aramid (e.g., para-aramid) spun yarn. The fiber sheath may be formed of the same blend of fibers as the body yarns. In another embodiment, the fiber sheath is formed of a different fiber blend, such as a blend of FR rayon and nylon (e.g., 90/10 blend). 
     The flame resistant fabric described herein may include the body yarns and the relatively tough yarns in any combination or orientation. For example, in some examples of the invention, the fabric may be a woven fabric that includes a warp direction and a fill direction. The body yarns will typically be provided in both the warp and fill direction. However, the relatively tough yarns may be included in only the warp direction, in only the fill direction, or in both the warp and fill direction so as to form a grid pattern within the fabric. Any desirable weave (e.g., plain, twill) or knit (e.g., single, double, plain, interlock) pattern may be used. 
     The relatively tough yarns may be located in the fabric relative to the body yarns in any desired ratio. The number of relatively tough yarns used in a rip stop as well as the frequency of the rip stops within the fabric may depend on the desired strength properties of the fabric and may be the same or different within and/or between the warp and/or fill direction of the fabric. Any number of relatively tough yarns greater than one may be used in each rip stop, and the number of relatively tough yarns within each rip stop need not be the same throughout the fabric. By way only of example, two relatively tough yarns, three relatively tough yarns, four relatively tough yarns, etc. may be used in a rip stop. Rip stops may be provided in either or both the warp and fill directions for every 40 body yarns, 35 body yarns, 30 body yarns, 25 body yarns, 20 body yarns, 15 body yarns, 10 body yarns, 5 body yarns, 4 body yarns, 3 body yarns, 2 body yarns, and 1 body yarn. The frequency at which rip stops are provided may be the same or different (1) within a direction of the fabric and/or (2) in different directions of the fabric. In some embodiments, at least two relatively tough yarns but less than 4 relatively tough yarns form a rip stop and between 5 to 30 body yarns, inclusive; between 5 and 25 body yarns, inclusive; between 5 and 20 body yarns, inclusive; between 5 and 15 body yarns, inclusive; between 5 and 10 body yarns, inclusive; between 10 and 30 body yarns, inclusive; between 10 and 25 body yarns, inclusive; between 10 and 20 body yarns, inclusive; and between 10 and 15 body yarns, inclusive are provided between adjacent rip stops in one or both directions of the fabric. 
     In some embodiments, the fabrics disclosed herein have a weight between 2-12 ounces per square yard (“osy”), inclusive; 3-10 osy, inclusive; 3-9 osy, inclusive; 3-8.5 osy, inclusive; 4-8 osy, inclusive; 4-7.5 osy, inclusive; 4-7 osy, inclusive; 5-7 osy, inclusive; 5.5-7 osy, inclusive; or 6-7 osy, inclusive. In some embodiments, the fabric weight is 6-7 osy, inclusive, and/or is less than or equal to 7 osy and/or less than or equal to 6.5 osy. 
     Specific, non-limiting embodiments of the invention are as follows: 
     Inventive Fabric 1 (“IF1”): A 6.5 osy woven fabric formed with (1) spun body yarns having a fiber blend of 70% FR rayon/20% para-aramid/10% nylon and (2) relatively tough yarns that were corespun yarns having a single 30 cotton count (English) 100% para-aramid spun core yarn and a fiber sheath of 70% FR rayon/20% para-aramid/10% nylon. The body yarns and relatively tough yarns were provided in both the warp and fill directions in a body yarn to relatively tough yarn ratio of 19:2 in the warp and 10:2 in the fill, meaning that a rip stop of two relatively tough yarns followed nineteen body yarns in a repeating pattern across the warp direction and a rip stop of two relatively tough yarns followed ten body yarns in a repeating pattern across the fill direction. The warp and fill densities were 69 ends/inch and 59 picks/inch, respectively. 
     Inventive Fabric 2 (“IF2”): A 6.5 osy woven fabric formed with (1) spun body yarns having a fiber blend of 70% FR rayon/20% para-aramid/10% nylon and (2) relatively tough yarns that were corespun yarns having a single 30 cotton count (English) 100% para-aramid spun core yarn and a fiber sheath of 90% FR rayon/10% nylon. The body yarns and relatively tough yarns were provided in both the warp and fill directions in a body yarn to relatively tough yarn ratio of 19:2 in the warp and 10:2 in the fill (as described above with respect to Inventive Fabric 1). The warp and fill densities were 69 ends/inch and 59 picks/inch, respectively. 
     Inventive Fabric 3 (“IF3”): A 6.5 osy woven fabric formed with (1) spun body yarns having a fiber blend of 65% FR rayon/25% para-aramid/10% nylon and (2) relatively tough yarns that were corespun yarns having a single 30 cotton count (English) 100% para-aramid spun core yarn and a fiber sheath of 65% FR rayon/25% para-aramid/10% nylon. Only body yarns were provided in the warp direction. Both body yarns and relatively tough yarns were provided in the fill direction in a body yarn to relatively tough yarn ratio of 10:2 in the fill direction, meaning that a rip stop of two relatively tough yarns followed ten body yarns in a repeating pattern across the fill direction. The warp and fill densities were 69 ends/inch and 59 picks/inch, respectively. 
     The tensile and tear strengths of Inventive Fabrics 1-3 were tested in compliance with GL-PD-07-12, Rev. 9 and compared against the Defender® M Ripstop fabric described above. Tensile strength is the force required to break a fabric under a load, and is measured in accordance with ASTM D5034-09 : Standard Test Method for Breaking Strength and Elongation of Textile Fabrics  ( Grab Test ) (2013 edition, incorporated herein by this reference). According to this method, a specimen is mounted centrally in clamps of a tensile machine and a force is applied until the specimen breaks. Values for the breaking force and the elongation of the test specimen are obtained from machine scales, dials, autographic recording charts, or a computer interfaced with the testing machine. The results are reported in pounds force (lbf). 
     Tear strength is a measure of the amount of force required to propagate in a fabric a tear after its initiation. The tear strength of fabrics is measured pursuant to ASTM D1424-09 ( Standard Test Method for Tearing Strength of Fabrics by Falling - Pendulum  ( Elmendorf - Type )  Apparatus  (2013 edition), incorporated by reference), and the results are reported in pounds force (lbf). 
     Pursuant to ASTM D1424-09, a slit of a specified size is cut into a fabric sample of a specified size. A clamp positioned on the fabric sample on each side of the slit to support the fabric sample. A weighted pendulum is released and swings down to apply a force to the fabric sample. The amount of force required to propagate the existing tear in the fabric is measured and that amount of force represents the tear strength of the fabric. 
     The testing results are reflected in Table 1. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 De- 
                   
                   
                   
                 GL-PD-07-12  
                   
               
               
                   
                 fender  
                   
                   
                   
                 Rev. 9 
                   
               
               
                   
                 M 
                   
                   
                   
                 Type III Re- 
                 Test 
               
               
                   
                 Ripstop 
                 IF1 
                 IF2 
                 IF3 
                 quirements* 
                 Method 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 O.A. Width  
                 66.3 
                 66.7 
                 66.9 
                 66.8 
                   
                 ASTM 
               
               
                 (in.) 
                   
                   
                   
                   
                   
                 D 
               
               
                 Cuttable  
                 65.0 
                 65.9 
                 66.0 
                 65.9 
                   
                 3774 
               
               
                 Width 
                   
                   
                   
                   
                   
                   
               
               
                 Weight  
                 6.6 
                 6.3 
                 6.3 
                 6.5 
                 6.0-7.0 
                 ASTM 
               
               
                 (osy) 
                   
                   
                   
                   
                   
                 D  
               
               
                 Construction 
                   
                   
                   
                   
                   
                 3776 
               
               
                 (EPI × PPI) 
                   
                   
                   
                   
                   
                   
               
               
                 EPI 
                 75 
                 73 
                 74 
                 74 
                 60 
                   
               
               
                 PPI 
                 56 
                 54 
                 53 
                 56 
                 50 
                   
               
               
                 Tensile  
                   
                   
                   
                   
                   
                 ASTM 
               
               
                 Strength (lbf) 
                   
                   
                   
                   
                   
                 D  
               
               
                 Dry 
                   
                   
                   
                   
                   
                 5034 
               
               
                 Warp 
                 163 
                 170 
                 171 
                 169 
                 110 
                   
               
               
                 Fill 
                 114 
                 122 
                 120 
                 130 
                 100 
                   
               
               
                 Wet 
                   
                   
                   
                   
                   
                   
               
               
                 Warp 
                 142 
                 148 
                 149 
                 149 
                 N/A 
                   
               
               
                 Fill 
                 105 
                 111 
                 108 
                 116 
                   
                   
               
               
                 Elmendorf  
                   
                   
                   
                   
                   
                 ASTM 
               
               
                 Tear (lbf) 
                   
                   
                   
                   
                   
                 D  
               
               
                 Dry 
                   
                   
                   
                   
                   
                 1424 
               
               
                 Warp 
                 17.8 
                 18.7 
                 19.5 
                 22.4 
                 12.0 
                   
               
               
                 Fill 
                 14 
                 23 
                 19.7 
                 21.9 
                 10.0 
                   
               
               
                 Wet 
                   
                   
                   
                   
                   
                   
               
               
                 Warp 
                 13.2 
                 14 
                 15.4 
                 14.4 
                 8.0 
                   
               
               
                 Fill 
                 8.8 
                 17.2 
                 14.6 
                 16.9 
                 6.0 
               
               
                   
               
               
                 *These requirements are the same for MIL-PRF-32635. 
               
            
           
         
       
     
     As evidenced in Table 1, the tensile and tear strengths for Inventive Fabrics 1-3 all complied with the Type III requirements of GL-PD-07-12, Rev. 9 and exceeded those of the Defender® M Ripstop control fabric, both when wet and when dry. 
     Embodiments of the fabric disclosed herein may be used in the construction of a variety of protective garments, either by itself or in combination with other fabrics, and is not limited for use in military applications. 
     EXAMPLES 
     A collection of exemplary embodiments, including at least some explicitly enumerated as “Examples” providing additional description of a variety of example types in accordance with the concepts described herein are provided below. These examples are not meant to be mutually exclusive, exhaustive, or restrictive; and the invention is not limited to these example examples but rather encompasses all possible modifications and variations within the scope of the issued claims and their equivalents. 
     Example 1. A flame resistant fabric having a warp direction and a fill direction, the fabric comprising a plurality of spun body yarns each formed of a body yarn fiber blend and provided in both the warp direction and the fill direction of the fabric, and a plurality of rip stops extending between at least some of the spun body yarns in at least one of the warp direction or the fill direction of the fabric, wherein each rip stop comprises at least two relatively tough yarns and wherein each relatively tough yarn comprises a core and a sheath, wherein the core comprises an 100% aramid spun yarn and the sheath comprises a sheath fiber blend. 
     Example 2. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the core comprises an 100% para-aramid spun yarn. 
     Example 3. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the sheath fiber blend comprises FR rayon fibers, aramid fibers, and nylon fibers. 
     Example 4. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the sheath fiber blend comprises 50-80% FR rayon fibers, 15-40% aramid fibers, and 5-20% nylon fibers. 
     Example 5. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the aramid fibers are para-aramid fibers. 
     Example 6. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the body yarn fiber blend and the sheath fiber blend are identical. 
     Example 7. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the body yarn fiber blend and the sheath fiber blend each comprises 50-80% FR rayon fibers, 15-40% aramid fibers, and 5-20% nylon fibers. 
     Example 8. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the body yarn fiber blend and the sheath fiber blend are identical. 
     Example 9. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein five to twenty-five spun body yarns are interposed between adjacent rip stops in the at least one of the warp direction or the fill direction. 
     Example 10. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein ten to twenty body yarns are interposed between adjacent rip stops in the at least one of the warp direction or the fill direction. 
     Example 11. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the plurality of rip stops extend between at least some of the spun body yarns in both the warp direction and the fill direction of the fabric. 
     Example 12. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the fabric comprises a weight between 5-7 ounces per square yard, inclusive. 
     Example 13. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the flame resistant fabric is devoid of filament yarns. 
     Example 14. A flame resistant fabric having a warp direction and a fill direction, the fabric comprising a plurality of spun body yarns each formed of a body yarn fiber blend and provided in both the warp direction and the fill direction of the fabric, wherein the body yarn fiber blend comprises 50-80% FR rayon fibers, 15-40% aramid fibers, and 5-20% nylon fibers, and a plurality of rip stops extending between at least some of the spun body yarns in at least one of the warp direction or the fill direction of the fabric, wherein each rip stop comprises at least two relatively tough yarns and wherein each relatively tough yarn comprises a core and a sheath, wherein the core comprises an 100% aramid spun yarn and the sheath comprises a sheath fiber blend comprising 50-80% FR rayon fibers, 15-40% aramid fibers, and 5-20% nylon fibers, and wherein five to twenty-five body yarns are interposed between adjacent rip stops in the at least one of the warp direction or the fill direction. 
     Example 15. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the core comprises an 100% para-aramid spun yarn. 
     Example 16. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the 15-40% aramid fibers in the body yarn fiber blend and the sheath fiber blend comprise 15-40% para-aramid fibers. 
     Example 17. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the body yarn fiber blend and the sheath fiber blend are identical. 
     Example 18. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the plurality of rip stops extend between at least some of the spun body yarns in both the warp direction and the fill direction of the fabric. 
     Example 19. The flame resistant fabric of any of the preceding or subsequent examples or combination of examples, wherein the fabric comprises a weight between 5-7 ounces per square yard, inclusive. 
     Example 20. A flame resistant fabric having a warp direction and a fill direction, the fabric comprising a plurality of spun body yarns each formed of a body yarn fiber blend and provided in both the warp direction and the fill direction of the fabric, wherein the body yarn fiber blend comprises 50-80% FR rayon fibers, 15-40% para-aramid fibers, and 5-20% nylon fibers, and a plurality of rip stops extending between at least some of the spun body yarns in both the warp direction and the fill direction of the fabric, wherein at least some of the plurality of rip stops consist of two relatively tough yarns and wherein each relatively tough yarn comprises a core and a sheath, wherein the core comprises an 100% para-aramid spun yarn and the sheath comprises a sheath fiber blend comprising 50-80% FR rayon fibers, 15-40% para-aramid fibers, and 5-20% nylon fibers, wherein the body yarn fiber blend and the sheath fiber blend are substantially identical, wherein ten to twenty body yarns are interposed between adjacent rip stops in the warp direction and the fill direction of the fabric, and wherein the fabric comprises a weight between 5-7 ounces per square yard, inclusive. 
     Different arrangements of the components described above, as well as components and steps not shown or described are possible. Similarly, some features and subcombinations are useful and may be employed without reference to other features and subcombinations. Embodiments of the invention have been described for illustrative and not restrictive purposes, and alternative embodiments will become apparent to readers of this patent. Accordingly, the present invention is not limited to the embodiments described above or depicted in the drawings, and various embodiments and modifications can be made without departing from the scope of the invention.