ABSTRACT
This chapter is aimed at reviewing the state of the art related to the preparation of polymer nanocomposites having tunable graphene loadings and summarizing their main distinct features. The current open literature describes several types of so-called “graphene,” which differ in the processes used to obtain it, namely: expansion, exfoliation, functionalization, oxidation, oxidation/reduction, etc. Thus, very often it becomes quite difcult to discriminate among the different “graphene products” and to avoid any misunderstanding: indeed, as an example, the use of reduced graphene oxide instead of “graphene” can inuence the overall nal properties of the polymer material, to which the nanoller is added, in a very different way with respect to the “graphene”
obtained through direct sonication, milling, or thermal expansion. Among the up-to-date methods exploited for obtaining and utilizing this nanoller in nanocomposite fabrication, the direct sonication from colloidal suspensions of graphite and the use of graphene nanoplatelets (GNP) (dened as graphene mono-or few layers, possibly bearing some functional groups attached to the carbon structure) are the most convenient in terms of cost and simplicity; they differ as far as the purity and the presence of process-induced defects are concerned. The former method involves a simple protocol based on lowenergy consumption and high volume production and allows obtaining graphene substantially without any defect. In addition, such a nanoller, obtained by direct exfoliation (i.e., without any chemical oxidation and subsequent reduction) in
Abstract ......................................................................................................................................................................................175 13.1 Methods for Obtaining Exfoliated Graphene from Graphite: An Overview ...................................................................176 13.2 Polymer-Graphene Nanocomposites............................................................................................................................... 180
13.2.1 Graphene Nanocomposites Using Thermoplastic Matrices ................................................................................ 180 13.2.1.1 Polyethylene: Graphene Nanocomposites........................................................................................... 180 13.2.1.2 Polypropylene-Graphene Nanocomposites ........................................................................................ 182 13.2.1.3 Polycarbonate-Graphene Nanocomposites ........................................................................................ 182 13.2.1.4 Poly(Vinyl Acetate)–Graphene Nanocomposites ............................................................................... 182 13.2.1.5 Poly(Vinyl Alcohol)–Graphene Nanocomposites .............................................................................. 182 13.2.1.6 Polystyrene-Graphene Nanocomposites ............................................................................................ 183 13.2.1.7 Poly(Lactic Acid)–Graphene Nanocomposites .................................................................................. 183 13.2.1.8 Polyurethane-Graphene Nanocomposites ......................................................................................... 183 13.2.1.9 Poly(Etherimide)–Graphene Nanocomposites ................................................................................... 183 13.2.1.10 Liquid Crystalline Polymer-Graphene Nanocomposites ................................................................... 183 13.2.1.11 Polyaniline-Graphene Nanocomposites ............................................................................................ 184 13.2.1.12 Polypyrrole-Graphene Nanocomposites ............................................................................................ 184 13.2.1.13 Poly(Ethylenedioxythiophene)–Graphene Nanocomposites .............................................................. 184 13.2.1.14 Poly(Ethylene Terephthalate)–Graphene Nanocomposites ................................................................ 184 13.2.1.15 Chitosan-Graphene Nanocomposites ................................................................................................ 185
13.2.2 Graphene Nanocomposites Using Thermosetting Matrices ................................................................................ 185 13.2.2.1 Epoxy-Graphene Nanocomposites .................................................................................................... 185 13.2.2.2 Hydrogel-Graphene Nanocomposites ................................................................................................ 186 13.2.2.3 Polyacrylate-Graphene Nanocomposites ........................................................................................... 187 13.2.2.4 PUR-Graphene Nanocomposites ....................................................................................................... 187 13.2.2.5 Elastomers-Graphene Nanocomposites ............................................................................................. 187
13.3 Conclusions ...................................................................................................................................................................... 187 References ................................................................................................................................................................................. 187
suitable common solvents, surfactants, or monomers to eventually polymerize, can be used for the preparation of both thermoplastic and thermoset polymer nanocomposites. GNP can be obtained by exploiting different exfoliation processes (i.e., milling, sonication, thermal expansion, etc.), usually in the presence of chemically reactive compounds that are used for the functionalization of the nanoller. Nowadays, they represent the most used type of “graphene” existing in the market. However, it will be shown that, despite their availability, they should be used with caution in that they can hardly be considered “real graphene,” because of the number of defects induced by the fabrication process still remaining in the structure.
