Carbon fiber composite material and process for producing the same

1. A process for producing a carbon fiber composite material comprising:

selecting an uncrosslinked elastomer having a spin-spin relaxation time (T 2 n ) of its network component of 100 to 3,000 μsec as measured under conditions of an observing nucleus of 1 H at 30° C. by the Hahn-echo method using pulsed NMR technique; and

substantially uniformly dispersing a plurality of carbon nanofibers into the elastomer by shear force at a temperature of 0 to 50° C. by an open-roll method using two rolls with a roll distance of 0.5 mm or less,

wherein the elastomer has an unsaturated bond or a group, having affinity to the carbon nanofiber.

2. The process for producing a 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 process for producing a 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 process for producing a 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. The process for producing a carbon fiber composite material according to claim 1 , wherein the carbon nanofibers have an average diameter of 0.5 to 500 nm.

6. The process for producing a carbon fiber composite material according to claim 1 , wherein a surface velocity ratio of the two rolls is from 1.05 to 3.00.

7. The process for producing a carbon fiber composite material according to claim 1 , further comprising crosslinking the elastomer in the composite material after the dispersion of the plurality of carbon nanofibers into the elastomer.

8. The process for producing a carbon fiber composite material according to claim 1 , wherein substantially uniform dispersion of the plurality of nanofibers includes:

separating aggregations of nanofibers; and

preventing reaggregation of nanofibers,

wherein the non-aggregated nanofibers in the final carbon fiber composite material are homogenously dispersed throughout the elastomer.

9. A process for producing a carbon fiber composite material comprising:

selecting an uncrosslinked elastomer having a spin-spin relaxation time (T 2 n ) of its network component of 100 to 3,000 μsec as measured under conditions of an observing nucleus of 1 H at 30° C. by the Hahn-echo method using pulsed NMR technique;

substantially uniformly dispersing a plurality of carbon nanofibers into the elastomer by shear force, wherein the elastomer has an unsaturated bond or a group, having affinity to the carbon nanofiber;

ensuring that the resulting carbon fiber composite material in an uncrosslinked form 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 n n) that is absent or 1,000 to 10,000 μsec, as measured under conditions of an observing nucleus of 1 H at 150° C. by the Hahn-echo method using pulsed NMR technique; and

ensuring that a fraction (fnn) of components having the second spin-spin relaxation time, as compared to the first spin-spin relaxation time, is less than 0.2.

10. A process for producing a carbon fiber composite material comprising:

selecting an elastomer (1) in an uncrosslinked form having a spin-spin relaxation time (T 2 n ) of its network component of 100 to 3,000 μsec as measured under conditions of an observing nucleus of 1 H at 30° C. by the Hahn-echo method using pulsed NMR technique and (2) having an unsaturated bond or a group with an affinity to a carbon nanofiber;

dispersing a plurality of the carbon nanofibers into the elastomer; and

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