Percolation threshold of carbon

MWCNTs are more effective than carbon black in improving the electrical properties of PP [47]. The addition of 5wt% of carbon black hardly improved the electrical properties of PP whereas 2 wt% of MWCNTs increased the conductivity by 5-6 orders of magnitude. Moreover, the percolation threshold of carbon black was much higher (10-20 wt%) as compared to CNTs [48]. 

Penu C, Hu G-H, Fernandez A, Marchal P, Choplin L (2012) Rheological and electrical percolation thresholds of carbon nanotube/polymer nanocomposites. Polym Eng Sci 52 2173 Pike GE, Seager CH (1974) Percolation and conductivity a computer study. I. Phys Rev B 10 1421... 

Herman , M. C. Manipulating the percolation threshold of carbon nanotubes in polymeric composites. Eindhoven University of Technology, Eindhoven, The Netherlands, 2008. 

Hermant MC, Smeets N, van Hal RC, Meuldijk J, Heuts H, Klumperman B, Herk AMV, Koning CE (2009) Influence of the molecular weight distribution on the percolation threshold of carbon nanotube-polystyrene composites. e-Polymers 9 248... 

Reticulate composites comprising needles of TTT-TCNQ (tetrathiotetra-cene-tetracyaiioquinodimethane) in poly(bisphenol-A-carbonate) were first described in the early 1980s. The composites were prepared by casting thin films from a solution of the components in o-dichloromethane. The composite contained a network of fine interconnected needle crystals of the CT salt and had a percolation threshold of 2-3 mass% of the CT salt, as shown in Fig. 8.22. 

A carbon black addition above a percolation threshold of 5 vol% increases the conductivity until a plateau is reached at 20 vol%. " As the level increases above 10 vol%, the viscosity of the filled polypropylene increases rapidly (see Figure 9.9). As with polyethylene, carbon black is preferentially contained in one phase of a two phase blend."" This phenomenon is used in practice to lower the concentration of carbon black required for a certain level of conductivity. Here, again, carbon black is concentrated in the preferred location. Carbon black and copper powder were used to improve connectivity of YBaCuO in ceramic superconductors. "" Dispersion of copper particles and the related changes in conductivity were enhanced by the presence of acrylic acid modifier. ... 

Some types of carbon black (Ketjenblack EC-2000 and Gulf ab 550-P) in certain cured epoxy resin systems showed to have a percolation threshold of less than 0.5 %wt., see Figure 5.23. The commercial relevance of this knowledge was recognised [33] and additional experiments were performed to obtain more insight in this phenomenon. Some experimental results of this investigation are collected in Table 5.6. 

Carbon black was selectively localized at the interface of a co-continuous PE/PS blend yielding a percolation threshold of 0.4 wt%. Karasz et al. [1997] have noted the use of polymer blends in light emitting diodes (LED). A mixture... 

Zhou and co-workers [28] measured the electrical conductivity/resistivity of carbon black filled linear low-density polyethylene (LLDPE) and blends of LLDPE with ethylene-methylacrylate (EMA). The percolation threshold of the blended polymer composite was significantly lower than that of the LLDPE composite, although in an EMA composite the threshold is higher. This effect was due to preferential absorption of the carbon black into the LLDPE due to phase separation and immiscibility in low-density polyethylene (LDPE)/EMA blends. The viscosity of polymers in the blend... 

Kilbride B E, Coleman J N, Fraysse J, Fournet P, Cadek M, Drury A, Hutzler S, Roth S and Blau W J (2002) Experimental observation of scaling laws for alternating current and direct current conductivity in polymer-carbon nanotube composite thin films, J Appl Phys 92 4024-4030. Sandler J K W, Kirk J E, Kinloch I A, Shaffer MSP and Windle A H (2003) Ultra-low electrical percolation threshold in carbon-nanotube-epoxy composites. Polymer 44 5893-5899. 

Yin et al. [68] investigated the critical resistivity, dispersivity, and percolation threshold of low-density polyethylene carbon black. Li et al. [69] investigated the electrical properties and crystallization behavior of four different kinds of carbon black-filled polypropylene composites, prepared by the melt mixing method. All showed typical characteristics of percolation, but noticeably different percolation thresholds. When using carbon black with a higher structure, smaller particle diameter, and larger surface area, the composite showed better electrical conductivity and a lower percolation threshold. 

Sf methacrylate copolymers as matrix for multiwalled carbon nanotubes. Under suitable preparation conditions (from common solvent), the electrical percolation threshold of nanocomposites of P(MMA-co-sfMA-H2F8) (30/70 mol/mol) with multiwalled carbon nanotubes (MWCNT) (type Nanocyl NC3150) is found to be below 0.1 wt%, that means extremely low compared to other polymer matrices. Details will be published elsewhere. The electrical volume conductivities of PMMA and a P(MMA-co-sfMA-H2F8) copolymer with MWCNT are plotted in Figure 11.25 versus the concentration of MWCNT. At similar contents of MWCNT, the percolation threshold of P(MMA-co-sfMA-H2F8)/MWCNT is lower and the electrical conductivity is higher than that of PMMA/MWCNT nanocomposites. We discuss this in terms of better compatibility of the fluorinated polymer with MWCNT, which was also indicated in former work [208]. 

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