Polymer/graphite nanocomposites electrical conduction

Shen et al. [75] measured the electrical conductivity of polyethylene/maleic anhydride-grafted polyethylene/graphite nanocomposites. Electrical conductivity and morphology were influenced by the polymer preparation method and could be explained in terms of percolation theory. 

Carbon materials provide electrical conduction through the pi bonding system that exists between adjacent carbon atoms in the graphite structure [182]. Electrical properties of nanocomposites based on conducting nanofillers such as EG [183-187], CNTs [188-190], and CNFs [191], dispersed in insulating polymer matrix have found widespread applications in industrial sectors. 

Kim, I. H., and Jeong, Y G. (2010], Polylactide/exfoliated graphite nanocomposites with enhanced thermal stability, mechanical modulus, and electrical conductivity. J. Polym. Sci. Polym. Phys., 8, pp. 850-858. 

Carbon nanotubes are one-dimensional carbon materials with high aspect ratio (greater than 1000) and excellent mechanical, electrical, and thermal properties when compared to other carbon materials, such as graphite and fuUerene. CNT is one of the most promising filler for nanocomposites and have generated great interests in the polymer industry due the technical applications in electrical conductivity, thermal conductivity, and improvements in mechanical properties (Choi et al. 2014). 

Chen GH, Wu DJ, Weng WG, Yan WL (2001) Preparation of polymer/graphite ctmducting nanocomposite by intercalation polymerization. J Appl Polym Sci 82 2506 Chen XM, Shen JW, Huang WY (2002) Novel electrically conductive polypropylene/graphene nanocomposites. J Mater Sci Lett 21 213... 

Exceptional mechanical properties along with remarkable electronic transport properties and thermal conductivity have made graphene the best carbon filler. Significant enhancement in mechanical properties of graphene-based polymer nanocomposites has been found (even with lower concentration) compared to those of the neat polymer and conventional graphite-based composites. Moreover, graphene/polymer nanocomposites exhibit several-fold increase in electrical conductivity and thermal conductivity. The conductive networks formed by graphene sheets result in considerable increase of the electrical conductivity and thermal conductivity of nanocomposites. As can be observed in Tables 7.1 and 7.2, property enhancements vary... 

Weng, W., Chen, G., Wu, D., Chen, X., Lu, J., Wang, P., 2004. Fabrication and characterisation of nylon 6/foliated graphite electrically conducting nanocomposite. Journal of Polymer Science Part B Polymer Physics 42, 2842—2856. 

Pan, YX., Yu, Z., Ou, Y, and Hu, G, (2000) A new process of fabricating electrically conducting nylon 6/graphite nanocomposites via intercalation polymerization. Journal of Polymer Science Part B Polymer Physics, 38,1626-1633. 

Sometimes it is necessary to have more than one material in nanofibers to mimic the structural and mechanical properties of the natural extracellular matrix. This can be done by a process called co-electrospinning, whereby blends of two different materials are electrospun to fabricate the scaffolds. Depending on the application one can make blends of different polymers or proteins or a combination of both. In our laboratory we have carried out extensive work on nanocomposite nanofibers fabricated from carbon nanotubes (CNTs). CNTs are a layer of graphite, one atom thick, rolled into a cylinder. CNT has a Young s modulus in the order of 1 TPa. " The toughness of CNT ranges from 6 to 30%. Incorporation of CNTs in polymeric and/or protein scaffolds not only improves the mechanical properties but gives unique electrical conductivity as well. We have fabricated co-electrospun scaffolds from various proteins, polymers and CNT. 

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... 

Recent studies showed that graphite nanoplatelets (GNP) or graphene could be used as a viable and inexpensive filler substitute for (3NTs (Fukushima and Drzal 2003). Typical values of the electrical percolation thresholds, which have been reported in the literature for graphene-based nanocomposites for selected polymer matrices, are presented in Table 13.3. The influence of graphene loading on the conductivity of one of the composites presented in Table 13.3 is shown in Fig. 13.2b. One can see that the electrical percolation thresholds achieved with graphene-based nanocomposites are often compared with those reported for CNT/polymer composites. 

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