Method of improving adhesion of carbon fibers with a polymeric matrix
A functionalized carbon fiber having covalently bound on its surface a partially cured epoxy or amine-containing sizing agent, wherein at least a portion of epoxide or amine groups in the sizing agent are available as uncrosslinked epoxide or amine groups, which corresponds to a curing degree of epoxide or amine groups of no more than about 0.6. Composites comprised of these functionalized carbon fibers embedded in a polymeric matrix are also described. Methods for producing the functionalized carbon fibers and composites thereof are also described.
1. A carbon fiber having covalently bound on its surface a partially cured sizing agent comprised of an epoxy resin, wherein said epoxy resin is covalently attached to a linking group that contains an accessible unsaturated group capable of reacting with a carbon-carbon double bond via a vinyl addition reaction, and at least a portion of epoxide groups in the sizing agent are available as uncrosslinked epoxide groups, which corresponds to a curing degree of epoxide groups of no more than about 0.6.
2. The carbon fiber of claim 1 , wherein said epoxy resin possesses a curing degree of epoxide groups of no more than about 0.5.
3. The carbon fiber of claim 1 , wherein said epoxy resin possesses a curing degree of epoxide groups of no more than about 0.4.
4. The carbon fiber of claim 1 , wherein said epoxy resin is comprised of a difunctional epoxy resin.
5. The carbon fiber of claim 4 , wherein said difunctional epoxy resin is selected from one or both of bisphenol A diglycidyl ether and ethylene glycol diglycidyl ether.
6. The carbon fiber of claim 1 , wherein said epoxy resin is a trifunctional or a higher functional epoxy resin.
7. The carbon fiber of claim 1 , wherein said partially cured sizing agent is a flexible gel.
8. A carbon fiber having covalently bound on its surface a partially cured amine-containing sizing, wherein at least a portion of amine groups in the sizing agent are available as uncrosslinked amine groups, which corresponds to a curing degree of amine groups of no more than about 0.6.
9. The carbon fiber of claim 8 , wherein said amine-containing sizing agent possesses a curing degree of amine groups of no more than about 0.5.
10. The carbon fiber of claim 8 , wherein said amine-containing sizing agent possesses a curing degree of amine groups of no more than about 0.4.
11. The carbon fiber of claim 8 , wherein said amine-containing sizing agent is comprised of an organoamine moiety containing at least two amine groups selected from primary and secondary amine groups.
12. The carbon fiber of claim 8 , wherein said partially cured amine-containing sizing agent is a flexible gel.
13. The carbon fiber of claim 8 , wherein said amine-containing sizing is covalently attached to a linking group that contains an accessible unsaturated group capable of reacting with a carbon-carbon double bond via a vinyl addition reaction.