Fillers graphenes

In the beginning, functionalization reactions were applied to fullerenes [1], later to CNTs [4,3], and recently to graphene [5]. Although both functionalization approaches have clear differences, they share the same intrinsic objective the creation of defects or doping within the surface of the carbon nanostructures in order to facilitate the interactions between the matrix and the filler. 

Goncalves, G., et al., Graphene oxide modified with PMMA viaATRP as a reinforcement filler. Journal of Materials Chemistry, 2010. 20(44) p. 9927-9934. 

Fig. 6.6 (a) A comparison of mechanical and thermal properties of PMMA hybrids with SWNT, expanded graphite (EGr) and functionalized graphene sheets (FGS). (b) Percentage synergy in hardness and modulus of the hybrids with binary nanocarbon fillers (from [44]). 

Fig. 6.7 (a) The variation of electrical conductivity of PVA-EG hybrid with increasing graphene content. Inset shows the dependence of dielectric constant for the hybrid, (b) The variation of conductivity of the polystyrene-graphene hybrid with filler content. Inset shows the four probe setup for in-plane and transverse measurements and the computed distributions of the current density for in-plane condition (reference [8]). 

Hu et al. showed a decrease in electrical resistivity of PVA by four orders of magnitude with a percolation threshold of 6 wt% [68], while biodegradable polylactide-graphene nanocomposites were prepared with a percolation threshold as low as 3 5wt% [46]. For polystyrene-graphene composites, percolation occurred at only 0.1 °/o of graphene filler, a value three times lower than those for other 2D-filler [69]. Figure 6.7(b) shows the variation of conductivity of the polystyrene-graphene composite with filler content. A sharp increase in conductivity occurs at 0.1 % (the percolation threshold) followed by a saturation. The inset shows the four probe set up for in-plane and trans-... 

Graphene-polymer nanocomposites share with other nanocomposites the characteristic of remarkable improvements in properties and percolation thresholds at very low filler contents. Although the majority of research has focused on polymer nanocomposites based on layered materials of natural origin, such as an MMT type of layered silicate compounds or synthetic clay (layered double hydroxide), the electrical and thermal conductivity of clay minerals are quite poor [177]. To overcome these shortcomings, carbon-based nanofillers, such as CB, carbon nanotubes, carbon nanofibers, and graphite have been introduced to the preparation of polymer nanocomposites. Among these, carbon nanotubes have proven to be very effective as conductive fillers. An important drawback of them as nanofillers is their high production costs, which... 

The percolation is usually very low, such as less than 1%. However, the polymers for electronics require high conductivity, thus a much higher content of filler is desired to form highly conductive networks in polymer matrix. Moreover, a good dispersion also helps to achieve percolation at low volume fraction of fillers. The graphene-polymer composites that were prepared via complete exfoliation of graphite and molecular-level dispersion of... 

Other, nanometer-scale forms of carbon, such as nanotubes and graphenes, have been proposed as ESD fillers, though their early use may be greater with engineering polymers. Carbon nanotubes (CNTs), in diameters of lO-lOOnm, can induce the conductivity needed for electrostatically paintable plastic automotive body panels, for example. They are also said to be replacing carbon black and fiber in small, detailed electronics applications [6-5]. 

Electrical/thermal conductive fillers Metalhc powders, carbon fiber, graphite, graphene Improves electrical and thermal conductivity... 

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