Graphene is a potential nanofiller that can dramatically improve the properties of polymer-based composites at a very low loading. This article reviews the state-of-the-art progress in the fabrication, properties, and uses of polymer composites with different kinds of graphene fillers. The results so far reported in the literature indicate that graphene/polymer composites are promising multifunctional materials with significantly improved tensile strength and elastic modulus, electrical and thermal conductivity, etc. Despite some challenges and the fact that carbon naotube/polymer composites are sometimes better in some particular performance, graphene/polymer composites may have wide potential applications due to their outstanding properties and the availability of graphene in a large quantity at low cost.

The Fabrication, Properties, and Uses of Graphene/Polymer Composites

Efficient reduction of graphene oxide (GO) by chemical, thermal, electrochemical, and photo-irradiation techniques has been reviewed. Particular emphasis has been directed towards the proposed reduction mechanisms of GO by different reducing agents and techniques. The advantages of using different kinds of reducing agents on the basis of their availability, cost-effectiveness, toxicity, and easy product isolation processes have also been studied extensively. We provide a detailed description of the improvement in physiochemical properties of reduced GO (RGO) compared to pure GO. For example, the electrical conductivity and electrochemical performance of electrochemically obtained RGO are much better than those of chemically or thermally RGO materials. We provide examples of how RGO has been used as supercapacitor electrode materials. Specific capacitance of GO increases after reduction and the value has been reported to be 100–300 F g−1. We conclude by proposing new environmentally friendly types of reducing agents that can efficiently remove oxygen functionalities from the surface of GO.

Recent advances in the efficient reduction of graphene oxide and its application as energy storage electrode materials

Carbon-family materials for flame retardant polymeric materials

TiO2 nanofibers (30–50 nm diameter), fabricated by the electro-spinning process, were modified with organo-silane agents via a coupling reaction and were grafted with carbohydrate molecules. The mixture was carbonized to produce a uniform coating of amorphous carbon on the surface of the TiO2 nanofibers. The TiO2@C nanofibers were characterized by high resolution electron microscopy (HRTEM), x-ray diffraction (XRD), x-ray photoelectron (XPS), Fourier transform infrared (FTIR) and UV-vis spectroscopy. The photocatalytic property of the functional TiO2 and carbon nanocomposite was tested via the decomposition of an organic pollutant. The catalytic activity of the covalently functionalized nanocomposite was found to be significantly enhanced in comparison to unfunctionalized composite and pristine TiO2 due to the synergistic effect of nanostructured TiO2 and amorphous carbon bound via covalent bonds. The improvement in performance is due to bandgap modification in the 1D co-axial nanostructure where the anatase phase is bound by nano-carbon, providing a large surface to volume ratio within a confined space. The superior photocatalytic performance and recyclability of 1D TiO2@C nanofiber composites for water purification were established through dye degradation experiments.

https://iopscience.iop.org/article/10.1088/2053-1591/1/1/015012/pdf

Carbon functionalized TiO2 nanofibers for high efficiency photocatalysis

Energetic graphene oxide: Challenges and opportunities

Graphite oxides (GOs) at various oxidation states were examined as fire retardants of epoxy resin. Excessive oxidation is detrimental to the fire retardant effect of GO because it generated a weak GO with reduced intumescent ability. GO manifested optimum fire retardant properties when it was properly oxidized due to the effective intumescence, demonstrating that intumescent GO needs to be strong enough to effectively push the epoxy resin matrix apart to cause efficient intumescence and generate a solid remnant char that acts as an efficient barrier. The fire retardant effect of GO was also reduced when a dispersion of GO in the epoxy resin was enhanced by sonication. This shows that the fine dispersion and disordering of layered structure of GO by the intercalation of epoxy molecules into the gallery of GO also reduced the intumescent ability, and the fire retardant effects of GO.

Graphite Oxides as Effective Fire Retardants of Epoxy Resin

Graphene is a two-dimensional nanocarbon that is currently being investigated for applications in a variety of areas. Graphene has unusual properties including a large surface area of 2,600 m·g, high thermal conductivity of ~3,000 W m·K, high electrical conductivity of ~550 S·cm, a high modulus of ~1 TPa, and a high aspect ratio of several hundreds. Aksay et al. recently reported that graphene sheets can be produced in bulk by the thermal expansion of sufficiently oxidized graphite oxide (GO). These exfoliated sheets are called functionalized graphene sheets (FGSs) because some of the oxygen containing groups such as epoxy groups remain after thermal treatment. FGSs have an affinity for polar solvents and polymers, as well as have a high electrical conductivity of about 10 S·cm. Polymers such as epoxy resin are generally good electrical insulators. However, an improvement in electric conductivity is necessary for applications that require electrostatic dissipation or electromagnetic radiation shielding. Nanocarbons with high conductivity and a large aspect ratio can be effectively utilized in the preparation of conductive polymer nanocomposites. Recent studies have demonstrated the emergence of FGS as fascinating conductive nanofillers with low percolation thresholds. In nanocomposites, nanofiller dispersion and interfacial interactions with the matrix polymer can be significantly enhanced through chemical or non-covalent physical modification of the nanofiller surface character. Many researchers have reported that polycyclic aromatic hydrocarbons such as pyrene or perylene are strongly adsorbed onto graphene sheets or carbon nanotubes through π-π interactions. We observed that the dispersibility of FGSs in the epoxy resin matrix was improved when the FGSs were treated with pyrene. This paper describes the effect of pyrene treatment on the dispersion, electric, and rheological properties of FGS/epoxy nanocomposites.

Soon Cheol Kim

Papers

Graphite Oxides as Effective Fire Retardants of Epoxy Resin

Effect of pyrene treatment on the properties of graphene/epoxy nanocomposites

Functionalized graphene sheets/polycarbonate nanocomposites compatibilized by poly(phenylenevinylene)