10 - Synthesis and Structural–Mechanical Property Characteristics of Graphene–Polymer Nanocomposites

Abstract

Graphene with extraordinary high elastic modulus, excellent mechanical strength, superior electrical and thermal conductivity has good prospects for applications as the material for fabricating composites, conductive thin films, electronics, fuel cells, and sensors. Large quantities of graphene oxide (GO) can be produced by wet chemical oxidation of graphite into a mixture of concentrated sulfuric acid, sodium nitrate, and potassium permanganate. GO is decorated with epoxide and hydroxyl groups in its basal plane carbon atoms, and carbonyl and carboxyl groups in its edge atoms. Hydrophilic GO is an electrical insulator and can react with water-soluble polymers only to form nanocomposites. As such, chemical or thermal reduction is needed to eliminate oxygenated groups in GO for restoring its electrical conductivity. Generally, GOs disperse poorly in organic solvents; the dispersion can be improved by surface modifying GO with appropriate organic functional groups. Functionalized GO facilitates the formation of a strong interfacial matrix–filler bonding and disperses more uniformly in the polymer matrix. An efficient stress transfer at the matrix–filler interface enables graphene to bear the applied load largely, resulting in the graphene/polymer nanocomposites with excellent mechanical performance. In addition, composite fabrication techniques affect the dispersion of graphene nanofillers in the polymer matrix markedly.