Flame resistant thermal liner, composite fabric, and garment

1. A flame resistant thermal liner comprising

(a) a nonwoven sheet comprising nanofibers of a synthetic polymer having an limiting oxygen index of at least 21, a mean flow pore of 10 micrometers or less, a thickness air permeability of 25 to 6000 cubic feet per min−micrometers (12 to 2880 cubic meters per square meter per min−micrometers), and an average thickness T 1 ; and

(b) a thermally stable flame resistant fabric attached to an outer surface of the nonwoven sheet, the fabric having an average thickness T 2 ; a surface of the thermally stable fabric being in contact with a surface of the nonwoven sheet;

wherein T 1 and T 2 are selected such that the ratio of T 1 to T 2 is less than 0.75.

2. The thermal liner of claim 1 , wherein T 1 and T 2 are selected such that the ratio of T 1 to T 2 is less than 0.30.

3. The thermal liner of claim 1 , wherein T 1 and T 2 are selected such that the ratio of T 1 to T 2 is greater than 0.120.

4. The thermal liner of claim 3 wherein, when the thermal liner is exposed to flame in accordance with ASTM D6413-99, the afterflame is no greater than 2 seconds.

5. The thermal liner of claim 4 wherein the nonwoven sheet comprising nanofibers comprises nanofibers made from polyimide, meta-aramid, para-aramid, polybenzazole, polybenzimidazole, or mixtures thereof; and the thermally stable flame resistant fabric comprises staple fiber and/or continuous filaments made from polyimide, meta-aramid, para-aramid, polybenzazole, polybenzimidazole, or mixtures thereof.

6. A flame resistant composite fabric system comprising an outer shell fabric and flame resistant thermal liner, the thermal liner comprising:

(a) a nonwoven sheet comprising nanofibers of a synthetic polymer having an limiting oxygen index of at least 21, a mean flow pore of 10 micrometers or less, a thickness air permeability of 25 to 6000 cubic feet per min−micrometers (12 to 2880 cubic meters per square meter per min−micrometers), and an average thickness T 1 ; and

(b) a thermally stable flame resistant fabric attached to an outer surface of the nonwoven sheet, the fabric having an average thickness T 2 ; a surface of the thermally stable fabric being in contact with a surface of the nonwoven sheet;

wherein T 1 and T 2 are selected such that the ratio of T 1 to T 2 is less than 0.75.

7. The flame resistant composite fabric system of claim 6 , wherein T 1 and T 2 are selected such that the ratio of T 1 to T 2 is less than 0.30.

8. The flame resistant composite fabric system of claim 6 , wherein T 1 and T 2 are selected such that the ratio of T 1 to T 2 is greater than 0.120.

9. A flame resistant protective garment comprising the composite fabric system of claim 8 .

10. The flame resistant composite fabric system of claim 6 further comprising a moisture barrier positioned between the outer shell fabric and the thermal liner.

11. The flame resistant composite fabric system of claim 10 , wherein the nonwoven sheet comprising nanofibers comprises nanofibers made from polyimide, meta-aramid, para-aramid, polybenzazole, polybenzimidazole, or mixtures thereof; and the thermally stable flame resistant fabric comprises staple fiber and/or continuous filaments made from polyimide, meta-aramid, para-aramid, polybenzazole, polybenzimidazole, or mixtures thereof.

12. The flame resistant composite fabric system of claim 10 , wherein T 1 and T 2 are selected such that the ratio of T 1 to T 2 is less than 0.30.

13. The flame resistant composite fabric system of claim 10 , wherein T 1 and T 2 are selected such that the ratio of T 1 to T 2 is greater than 0.120.

14. A flame resistant protective garment comprising the composite fabric system of claim 13 .