Power transmission belt containing short high molecular weight polyacrylonitrile fiber

1. An endless power transmission belt having

(1) a tension section;

(2) a cushion section; and

(3) a load-carrying section disposed between said tension section and cushion section, and the belt containing an elastomeric composition comprising

(a) a cross-linked rubber selected from the group consisting of ethylene alpha-olefin elastomer, hydrogenated acrylonitrile rubber, natural rubber, polybutadiene, polychloroprene and styrene-butadiene rubber; and

(b) from 1 to 50 phr of high molecular weight polyacrylonitrile staple fiber having a modulus of 5.5 GPa to 16.5 GPa, a number average molecular weight of 150,000 to 500,000, a specific gravity of 1.1 to 1.2, a diameter in a range of from about 5 to about 15 microns, and a length of from about 0.5 to about 15 mm.

2. The endless power transmission belt of claim 1 , wherein said high molecular weight polyacrylonitrile staple fiber has properties including a density of about 1.18 gm/cm 3 , an average length of about 0.5 to about 10 mm, an average diameter of about 12 microns, an average denier of about 1.2 dtex (1.1 denier), a tensile strength of about 1100 MPa, a modulus of about 13.8 GPa, and an elongation of about 12%.

3. The endless power transmission belt of claim 1 wherein the elastomeric composition further comprises at least one additional chopped fiber selected from the group consisting of aramid, nylon, polyester, PTFE, fiberglass, and cotton.

4. The endless power transmission belt of claim 1 wherein the elastomeric composition further comprises a filler selected from carbon black, silica, clay, exfoliated clay, talc, mica, calcium carbonate, starch, and wood flour.

5. The endless power transmission belt of claim 1 wherein the elastomeric composition further comprises carbon black.

6. The endless power transmission belt of claim 1 wherein the amount of high molecular weight polyacrylonitrile staple fiber ranges from 1 to 20 phr.

7. The endless power transmission belt of claim 1 wherein said elastomer composition is in the cushion section of the belt.

8. The endless power transmission belt of claim 1 wherein said elastomer composition is in the load-carrying section of the belt.

9. The endless power transmission belt of claim 1 wherein said elastomer composition is in the tension section of the belt.

10. The endless power transmission belt of claim 1 wherein said elastomeric composition comprises EPDM.

11. The endless power transmission belt of claim 1 wherein said elastomeric composition comprises hydrogenated acrylonitrile rubber.

12. The endless power transmission belt of claim 1 wherein said elastomeric composition comprises styrene-butadiene rubber and natural rubber.

13. The endless power transmission belt of claim 1 wherein said elastomeric composition comprises polybutadiene and natural rubber.

14. The endless power transmission belt of claim 1 wherein said elastomeric composition comprises polychloroprene rubber.

15. The endless power transmission belt of claim 1 wherein said high molecular weight polyacrylonitrile staple fiber comprises an acrylonitrile content of at least 85 percent, based on weight of acrylonitrile monomer content to total monomer content of the pre-polymerization mixture.

16. The endless power transmission belt of claim 15 , wherein the acrylonitrile content is in excess of 89 percent.

17. The endless power transmission belt of claim 15 wherein said high molecular weight polyacrylonitrile staple fiber further comprises about 8.5 percent by weight of methyl methacrylate or vinyl acetate as co-monomer.