Polymer-graphene nanocomposites
Provided herein is technology relating to polymer-graphene nanocomposites and particularly, but not exclusively, to methods for producing polymer-graphene nanocomposites using master batches comprising graphene and a polymer or polymer precursor. The resulting polymer-graphene nanocomposites comprise a high degree of exfoliation and dispersion of graphene nanoplatelets within the polymer matrix.
1. A master batch composition for making a polymer nanocomposite, the master batch composition comprising a polymer, wherein the polymer is a poly(vinyl lactam), a polyacrylamide, a thermoplastic polymer, thermoset polymer, polyethylene polymer, polypropylene polymer, polycarbonate polymer, unsaturated polyester, polyvinylchloride, or epoxy vinyl ester, or epoxy and at least 20% by weight exfoliated graphene.
2. The master batch composition of claim 1 comprising graphene and a poly(vinylpyrrolidone) in a weight ratio of 1:1 to 1:4.
3. The master batch composition of claim 1 comprising graphene and a thermoplastic polymer in a weight ratio of 1:1 to 1:4.
4. The master batch composition of claim 1 wherein the average thickness of the graphene is less than 10 atomic layers, a minimum of 5% of the graphene is single atomic layer graphene, and the oxygen content of the graphene is less than 1%.
5. The master batch composition of claim 1 wherein less than 10% of the graphene nanoplatelets have a maximum diameter of less than 0.5 microns.
6. The master batch composition of claim 1 comprising a poly(vinylpyrrolidone) that has a number average molecular weight of less than or equal to approximately 10,000 u.
7. A method of making a master batch composition for producing a polymer nanocomposite, the method comprising:
a) mixing a slurry of graphene, wherein the slurry of graphene is produced by:
i) treating graphite in an N-alkyl-pyrrolidone to produce solvent exfoliated graphene in the N-alkyl-pyrrolidone;
ii) removing most of the N-alkyl-pyrrolidone to produce a concentrated solution or dispersion of graphene in the N-alkyl-pyrrolidone; and
iii) adding a solvent to the graphene in N-alkyl-pyrrolidone to produce the slurry of graphene in the solvent system in a solvent system with a polymer; and
b) removing the solvent system to produce a master batch comprising from 20% to 60% exfoliated graphene.
8. The method of claim 7 wherein the mixing is high shear mixing.
9. The method of claim 7 wherein the polymer is a polyvinyl lactam or a thermoplastic polymer.
10. The method of claim 7 wherein the solvent is xylenes or methanol.
11. The method of claim 7 wherein the concentrated solution or dispersion of graphene in the N-alkyl-pyrrolidone comprises 2% to 8% graphene.
12. The method of claim 7 comprising filtration to remove the N-alkyl-pyrrolidone.
13. The method of claim 7 wherein the solvent system comprises 2% to 30% N-alkyl-pyrrolidone and 70% to 98% solvent.
14. A method of making a graphene/thermoplastic master batch consisting of the steps:
a) concentrating a solution or stable dispersion of exfoliated graphene above the solubility and stable dispersion limit of the exfoliated graphene;
b) dissolving a thermoplastic polymer in the graphene/solvent slurry in a ratio of 1:1 to 1:5 graphene to polymer; and
c) removing the solvent with continuous mixing to isolate the resultant graphene/polymer master batch as a solid.
15. A method of making a graphene/polymer master batch, the method comprising:
a) exfoliating graphene in a polymerizable solvent, wherein the polymerizable solvent is N-vinyl pyrrolidone or N,N-dimethyl acrylamide to provide a dispersion of exfoliated graphene in the polymerizable solvent;
b) polymerizing the polymerizable solvent to produce a graphene/polymer master batch.