US 7,601,421 B2 · Fabrication of carbon nanotube reinforced epoxy polymer composites using functionalized carbon nanotubes

Abstract

The present invention is directed to methods of integrating carbon nanotubes into epoxy polymer composites via chemical functionalization of carbon nanotubes, and to the carbon nanotube-epoxy polymer composites produced by such methods. Integration is enhanced through improved dispersion and/or covalent bonding with the epoxy matrix during the curing process. In general, such methods involve the attachment of chemical moieties (i.e., functional groups) to the sidewall and/or end-cap of carbon nanotubes such that the chemical moieties react with either the epoxy precursor(s) or the curing agent(s) (or both) during the curing process. Additionally, in some embodiments, these or additional chemical moieties can function to facilitate dispersion of the carbon nanotubes by decreasing the van der Waals attractive forces between the nanotubes.

Claims71

Dependent claims

A method comprising the steps of:

a) dispersing functionalized CNTs in a solvent to form a dispersion;
wherein the functionalized CNTs comprise oxidized, fluorinated CNTs;
wherein the oxidized, fluorinated CNTs are prepared by a process comprising:
a1) oxidizing unfunctionalized CNTs to form oxidized CNTs comprising opened ends;
wherein the opened ends comprise carboxylic acid groups;
and
a2) fluorinating the oxidized CNTs to form the oxidized, fluorinated CNTs;
wherein the fluorinating step is conducted after the oxidizing step;
and
wherein the fluorinating step comprises attaching fluorine moieties to sidewalls of the oxidized CNTs;
b) adding an epoxy resin to the dispersion to form a mixture;
c) removing the solvent from the mixture to form a substantially solvent-free mixture;
d) adding a curing agent to the substantially solvent-free mixture;
and
e) curing the substantially solvent-free mixture to form a CNT-epoxy composite;
wherein the functionalized CNTs are dispersed and integrated in the CNT-epoxy composite.

13 more elements

A method comprising the steps of:

a) dispersing functionalized CNTs in a first solvent to form a dispersion of functionalized CNTs;
wherein the functionalized CNTs comprise fluorinated, hydroxyl-functionalized CNTs;
wherein the fluorinated, hydroxyl-functionalized CNTs are prepared by a process comprising:
a1) reacting unfunctionalized CNTs with fluorine to form fluorinated CNTs;
a2) dispersing the fluorinated CNTs in a second solvent to form a dispersion of fluorinated CNTs;
a3) reacting a dialcohol with a metal hydroxide to form a metal salt of the dialcohol;
and
a4) reacting the metal salt of the dialcohol with the fluorinated CNTs to form the fluorinated, hydroxyl-functionalized CNTs;
b) adding an epoxy resin to the dispersion of functionalized CNTs to form a mixture;
c) removing the first solvent from the mixture to form a substantially solvent-free mixture;
d) adding a curing agent to the substantially solvent-free mixture;
and
e) curing the substantially solvent-free mixture to form a CNT-epoxy composite;
wherein the functionalized CNTs are dispersed and integrated in the CNT-epoxy composite.

11 more elements

A CNT-epoxy polymer composite prepared by a process comprising the steps of:

a) dispersing functionalized CNTs in a first solvent to form a dispersion of functionalized CNTs;
wherein the functionalized CNTs comprise sidewall carboxylic acid-functionalized CNTs;
wherein the sidewall carboxylic acid-functionalized CNTs are prepared by a process comprising:
a1) dispersing unfunctionalized CNTs in a second solvent to form a dispersion of unfunctionalized CNTs;
a2) adding an organic acyl peroxide of a dicarboxylic acid to the dispersion of unfunctionalized CNTs to form a reaction mixture;
and
a3) heating the reaction mixture to form free radicals;
wherein the free radicals are of the type HO(O)C—(CH2)n.;
and
wherein the free radicals react with sidewalls of the unfunctionalized CNTs to form the sidewall carboxylic acid-functionalized CNTs;
b) adding an epoxy resin to the dispersion of functionalized CNTs to form an epoxy mixture;
c) removing the first solvent from the epoxy mixture to form a substantially solvent-free mixture;
d) adding a curing agent to the substantially solvent-free mixture;
and
e) curing the substantially solvent-free mixture to form the CNT-epoxy polymer composite;
wherein the functionalized CNTs are dispersed and integrated in the CNT-epoxy polymer composite.