Crystallized meta-aramid blends for improved flash fire and arc protection
A yarn, fabric, and garment suitable for use in arc and flame protection and having improved flash fire protection contains a majority, by weight, of meta-aramid fibers having a degree of crystallinity of at least 20%, and a minority of modacrylic fibers, para-aramid fibers, and antistatic fibers. Garments made from the yarns provide thermal protection such that a wearer would experience less than a 65 percent predicted body burn when exposed to a flash fire exposure of 4 seconds per ASTM F1930, while maintaining a Category 2 arc rating per ASTM F1959 and NFPA 70E.
1. A yarn for use in arc and flame protection consisting essentially of:
(a) 50 to 80 weight percent meta-aramid fiber having a degree of crystallinity of at least 20%;
(b) 10 to 30 weight percent modacrylic fiber;
(c) 5 to 20 weight percent para-aramid fiber; and
(d) 1 to 3 weight percent antistatic fiber;
said percentages on the basis of components (a), (b), (c), and (d).
2. The yarn of claim 1 consisting essentially of:
(a) 65 to 75 weight percent meta-aramid fiber;
(b) 15 to 25 weight percent modacrylic fiber;
(c) 5 to 15 weight percent para-aramid fiber; and
(d) 2 to 3 weight percent antistatic fiber.
3. The yarn of claim 1 wherein the anti-static component comprises carbon or metal.
4. The yarn of claim 1 with the meta-aramid fiber has a degree of crystallinity in a range from 20 to 50%.
5. A fabric suitable for use in arc and flame protection comprising a yarn consisting essentially of:
(a) 50 to 80 weight percent meta-aramid fiber having a degree of crystallinity of at least 20%;
(b) 10 to 30 weight percent modacrylic fiber;
(c) 5 to 20 weight percent para-aramid fiber; and
(d) 1 to 3 weight percent antistatic fiber;
said percentages on the basis of components (a), (b), (c), and (d);
the fabric having a basis weight in the range of 186.5 to 237 grams per square meter (5.5 to 7 ounces per square yard).
6. The fabric of claim 5 wherein the yarn consists essentially of:
(a) 65 to 75 weight percent meta-aramid fiber;
(b) 15 to 25 weight percent modacrylic fiber;
(c) 5 to 15 weight percent para-aramid fiber; and
(d) 2 to 3 weight percent antistatic fiber.
7. The fabric of claim 5 having a char length according to ASTM D-6413-99 of less than 6 inches.
8. The fabric of claim 5 having arc resistance according to ASTM F-1959-99 of at least 1.1 calories per square centimeter per ounce per square yard of fabric.
9. The fabric of claim 8 wherein the arc resistance is at least 1.3 calories per square centimeter per ounce per square yard of fabric.
10. The fabric of claim 5 wherein the meta-aramid fiber has a degree of crystallinity in a range from 20 to 50%.
11. The fabric of claim 5 having a shrinkage of 5% or less after 10 wash cycles.
12. A garment suitable for use in arc and flame protection comprising a fabric consisting essentially of:
(a) 50 to 80 weight percent meta-aramid fiber having a degree of crystallinity of at least 20%;
(b) 10 to 30 weight percent modacrylic fiber;
(c) 5 to 20 weight percent para-aramid fiber; and
(d) 1 to 3 weight percent antistatic fiber;
said percentages on the basis of components (a), (b), (c), and (d)
the fabrics having a basis weight in the range of 186.5 to 237 grams per square meter (5.5 to 7 ounces per square yard).
13. The garment of claim 12 wherein the fabric consists essentially of:
(a) 65 to 75 weight percent meta-aramid fiber;
(b) 15 to 25 weight percent modacrylic fiber;
(c) 5 to 15 weight percent para-aramid fiber; and
(d) 2 to 3 weight percent antistatic fiber.
14. The garment of claim 12 , providing thermal protection equivalent to less than a 65% body burn at a 4 sec flame exposure per ASTM F1930, while maintaining a Category 2 arc rating per ASTM F1959 and NFPA 70E.
15. The garment of claim 12 wherein the fabric has a shrinkage of 5% or less after 10 wash cycles.