Switchable ionic adhesive coating for recyclable carbon fiber

1. A carbon fiber reinforced plastic matrix, comprising:

at least one surface functionalized carbon fiber; and

at least one carboxylic acid functionalized matrix polymer;

wherein

the carbon fiber is surface functionalized with one or more organoamines selected from a diethylamine, amidine, diguanidine, guanidine, amine dendrimer, or polyguanidine group.

2. The carbon fiber reinforced plastic matrix of claim 1 , wherein the organoamine is attached to the carbon fiber with a linker comprising a (C 1 -C 10 )alkylene group.

3. The carbon fiber reinforced plastic matrix of claim 2 , wherein the linker is a —(C 1 -C 10 )alkylenesiloxy, —(C 1 -C 10 )alkylene-C(O)—, or a —(OCH 2 —CH 2 ) n —O— group, where n is an integer from 1 to 10.

4. The carbon fiber reinforced plastic matrix of claim 1 , wherein the organoamine is selected from the group consisting of 1,1′-((ethylimino)bis(trimethylene))diguanidine and a guanidine dendrimer.

5. The carbon fiber reinforced plastic matrix of claim 1 , wherein the matrix polymer is a thermoset polymer selected from the group consisting of polyester, polyvinyl ester, polyurethane and copolymers thereof.

6. The carbon fiber reinforced plastic matrix of claim 1 , wherein the matrix polymer is a thermoplastic polymer selected from the group consisting of polyacetals, nylons, polyethylene terephthalate (PET) and copolymers thereof.

7. A method for making a carbon fiber reinforced plastic matrix, the method comprising:

contacting at least one surface functionalized carbon fiber with at least one carboxylic acid functionalized matrix polymer to obtain the carbon fiber reinforced plastic matrix,

wherein the carbon fiber is surface functionalized with one or more organoamines selected from a diethylamine, amidine, diguanidine, guanidine, amine dendrimer, or polyguanidine group.

8. The method of claim 7 , wherein the one or more organoamines of the surface functionalized carbon fiber are attached to the carbon fiber with a linker comprising a (C 1 -C 10 )alkylene group.

9. The method of claim 7 , further comprising:

oxidizing at least one surface of a carbon fiber to provide a carboxylic acid functionalized carbon fiber; and

contacting the carboxylic acid functionalized carbon fiber with one or more organoamines or organoamine precursors to provide the carbon fiber surface functionalized with one or more organoamines.

10. The method of claim 7 further comprising:

oxidizing at least one surface of a carbon fiber to provide a mixture of carboxylic acid and ester groups on the carbon fiber surface;

hydrolyzing the ester groups to carboxylic acid groups to provide a carboxylic acid functionalized carbon fiber; and

contacting the carboxylic acid functionalized carbon fiber with the one or more organoamines or organoamine precursors to provide the carbon fiber surface functionalized with one or more organoamines.

11. The method of claim 7 , further comprising:

oxidizing at least one surface of a carbon fiber to provide a mixture of carboxylic acid and ester groups on the carbon fiber surface;

reducing the mixture of carboxylic acid and ester groups on the carbon fiber surface to hydroxyl groups; and

contacting hydroxyl groups with one or more organoamine precursors to provide the carbon fiber surface functionalized with one or more organoamines.

12. A method for recycling a carbon fiber reinforced plastic matrix, the method comprising:

contacting the carbon fiber reinforced plastic matrix with an acid;

decomposing the matrix to provide a decomposed matrix and carbon fiber; and

separating the decomposed matrix from the carbon fiber to obtain recycled carbon fiber;

wherein

the carbon fiber reinforced plastic matrix comprises at least one surface functionalized carbon fiber and at least one carboxylic acid functionalized matrix polymer; and

the carbon fiber is surface functionalized with one or more organoamines selected from a diethylamine, amidine, diguanidine, guanidine, amine dendrimer, or polyguanidine group.

13. The method of claim 12 , wherein the organoamine of the surface functionalized carbon fiber is attached to the carbon fiber with a linker comprising a (C 1 -C 10 )alkylene group.

14. The method of claim 12 , wherein contacting the carbon fiber reinforced plastic matrix with an acid occurs in the presence of a polar protic solvent.

15. The method of claim 14 , wherein the polar protic solvent of the contacting step is water, a linear or branched (C 1 -C 10 ) alcohol, a carboxylic acid, or mixtures thereof.

16. The method of claim 12 , wherein the acid of the contacting step is an acidic gas.

17. The method of claim 16 , wherein the acidic gas of the contacting step is sulfur dioxide, supercritical carbon dioxide, carbonyl sulfide, carbon disulfide, boron trifluoride, nitrogen dioxide, phosphorous pentafluoride, hydrogen chloride, hydrogen fluoride, or hydrogen bromide.

18. The method of claim 12 , further comprising re-functionalization of the surface of the recycled carbon fiber after the separating step.

19. The carbon fiber reinforced plastic matrix of claim 1 , wherein the organoamine is selected from the group consisting of an amidine, diguanidine, guanidine, amine dendrimer, and a polyguanidine group.