Carbon fiber composite material and process for producing the same

1. A carbon fiber composite material comprising an elastomer and a plurality of carbon nanofibers substantially uniformly dispersed in the elastomer, wherein:

the elastomer has an unsaturated bond or a group, having affinity to the carbon nanofibers;

the elastomer in the composite material is in its uncrosslinked form; and

the composite material has a first spin-spin relaxation time (T 2 n ) of 100 to 3000 μsec and a second spin-spin relaxation time (T 2 nn ) of being absent or 1000 to 10,000 μsec, and a fraction (fnn) of components having the second spin-spin relaxation time of less than 0.2, as measured under conditions of an observing nucleus of 1 H at 150° C. by the Hahn-echo method using pulsed NMR technique.

2. The carbon fiber composite material according to claim 1 , wherein the elastomer has a weight average molecular weight of 5,000 to 5,000,000.

3. The carbon fiber composite material according to claim 1 , wherein the elastomer has, in at least one of its main chain, side chains and terminal chains, at least one member selected from the group consisting of a double bond, a triple bond, a carbonyl group, a carboxyl group, a hydroxyl group, an amino group, a nitrile group, a ketone group, an amide group, an epoxy group, an ester group, a vinyl group, a halogen group, a urethane group, a biuret group, an allophanate group, and a urea group.

4. The carbon fiber composite material according to claim 1 , wherein the elastomer in the composite material is one of natural rubber (NR) and nitrile rubber (NBR).

5. A carbon fiber composite material comprising an elastomer and a plurality of carbon nanofibers substantially uniformly dispersed in the elastomer, wherein the elastomer in the composite material is in its uncrosslinked form, and the composite material has a first spin-spin relaxation time (T 2 n ) of 100 to 3,000 μsec and a second spin-spin relaxation time (T 2 nn ) of being absent or 1,000 to 10,000 μsec, and a fraction (fnn) of components having the second spin-spin relaxation time of less than 0.2, as measured under conditions of an observing nucleus of 1 H at 150° C. by the Hahn-echo method using pulsed NMR technique.

6. A carbon fiber composite material comprising an elastomer and a plurality of carbon nanofibers substantially uniformly dispersed in the elastomer, wherein the elastomer in the composite material is in its crosslinked form, and the composite material has a first spin-spin relaxation time (T 2 n ) of 100 to 2,000 μsec and a second spin-spin relaxation time (T 2 nn ) of being absent or 1,000 to 5,000 μsec, and a fraction (fnn) of components having the second spin-spin relaxation time of less than 0.2, as measured under conditions of an observing nucleus of 1 H at 150° C. by the Hahn-echo method using pulsed NMR technique.

7. The carbon fiber composite material according to claim 1 , wherein the elastomer in the composite material is in its uncrosslinked form and the composite material has a flow temperature higher than the inherent flowing temperature of the elastomer by 20° C. or more.

8. The carbon fiber composite material according to claim 1 , wherein each carbon nanofiber has an average diameter of 0.5 to 500 nm.

9. The carbon fiber composite material according to claim 5 , wherein the elastomer in the composite material is in its uncrosslinked form and the composite material has a flow temperature higher than the inherent flowing temperature of the elastomer by 20° C. or more.

10. The carbon fiber composite material according to claim 5 , wherein each carbon nanofiber has an average diameter of 0.5 to 500 nm.

11. The carbon fiber composite material according to claim 6 , wherein each carbon nanofiber has an average diameter of 0.5 to 500 nm.

12. A carbon fiber composite material comprising an elastomer and a plurality of carbon nanofibers substantially uniformly dispersed in the elastomer, wherein:

the elastomer has an unsaturated bond or a group, having affinity to the carbon nanofibers;

the elastomer in the composite material is in its crosslinked form; and

the composite material has a first spin-spin relaxation time (T 2 n ) of its of 100 to 2,000 μsec and a second spin-spin relaxation time (T 2 nn ) of being absent or 1,000 to 10,000 μsec, and a fraction (fnn) of components having the second spin-spin relaxation time of less than 0 . 2 , as measured under conditions of an observing nucleus of 1 H at 150° C. by the Hahn-echo method using pulsed NMR technique.