Polyethylene electrical conductivity

T. Tao, L. Zhang, J. Ma, C. Li, Production of flexible and electrically conductive polyethylene-carbon nanotube shish-kebab structures and their assembly into thin films, Ind. Eng. Chem. Res, vol. 51, pp. 5456-5460, 2012. 

Fig.36. Variation in electrical conductivity (o) with molecular weight for polyethylene composites filled with 4% by volume carbon black, demonstrating the effects of orientation (I), degradation (II) and flow-induced segregation of carbon black aggregates (III). ( ) injection moulded (O) compression moulded (unoriented) [181]...

Although the motion of protons does not lead to electrical conduction in the case of benzoic acid, electronic and even ionic conductivity can be found in other molecular crystals. A well-studied example of ionic conduction is a film of polyethylene oxide (PEO) which forms complex structures if one adds alkaline halides (AX). Its ionic conductivity compares with that of normal inorganic ionic conductors (log [cr (Q cm)] -2.5). Other polymers with EO-units show a similar behavior when they are doped with salts. Lithium batteries have been built with this type of... 

Table IV contains some comparative data regarding the electrical conductivity of some polychelates based on Fe3+ and Mn2+. The data dealing with electrical conductivity of polychelates, the starting polymers (for polyethylene terephthalate,

Banford et al. studied the radiation effects on electrical properties of low-density polyethylene (LDPE) at 5 K with the use of a 60Co gamma source and a thermal nuclear reactor [86]. They reported that both the electrical conductivity and the dielectric breakdown strength of LDPE at 5 K were not significantly affected by radiation absorbed doses up to 10s Gy, but an erratic pulse activity under high applied fields was observed in the sample irradiated at 106 Gy. 

When seeking a polymer material for a CNT-based strain gauge, ductility and ease of processing are the key requirements. For that reason, polymethyl methacrylate (PMMA) and polyethylene (PE) are two candidate materials. Studies on the electrical conductivities of CNT-PMMA composites reported minimum percolation thresholds ranging from 0.084 to 1.3 wt% which depend on the type of CNT (SWNT or MWNT) and the dispersion technique. Such values are much lower than percolation thresholds reported for CNT-PE which rise up to 15 wt% (38). As a consequence, much higher conductivity values were reported for CNT-PMMA composites. For this reason, a PMMA matrix will be considered for the current... 

An aqueous dispersion consisting of polyethylene glycol containing a (2,3-dihydro-thieno[3,4-b][l,4]dioxin-2-yl)-methanol terminus has been prepared. This material exhibited electrical conductivities, visible light transmittances, and good processability. 

Composites containing metal particles provide a clear example of the percolation behaviour described in Section 8.3. By way of illustration we can cite the results shown in Table 8.1 for a dispersion of approximately spherical nickel particles (about 10 pm in diameter) in a low-density polyethylene. Here conductivity is lost entirely at concentrations below about 20% by volume of metal, corresponding to about 70% by mass. Nevertheless, conductive paints, which are frequently used for painting electrodes on to electrical test specimens and devices, work in just this way. 

The electric conductivity of polyethylene can be improved by addition of manyfillers. Figure 15.17 shows the effect of aspect ratio of the fiber on the electric conductivity of polyethylene filled with carbon fiber. Depending on the aspect ratio, different levels of carbon fiber are needed to obtain the same effect. When a very high aspect ratio is used, 2 vol% carbon fiber gives the same effect as can be obtained with 30 vol% of carbon fiber having aspect ratio of 1. Compared with... 

Figure 15.17. Electric conductivity of polyethylene filled with carbon fibers of different aspect ratio vs. volume content. [Adapted, by permission, from Agari Y, Ueda A, Nagai S, J. Appl. Polym. Sci., 52, No.9,1994, 1223-31.]...

Heat conductivity of composite materials are severely and adversely affected by structural defects in the material. These defects are due to voids, uneven distribution of filler, agglomerates of some materials, unwetted particles, etc. Figure 15.18 shows the effect of filler concentration on thermal conductivity of polyethylene. Graphite, which is a heat conductive material, increases conductivity at a substantially lower concentration than does quartz. These data agree with the theoretical predictions of model. Figure 15.19 shows the effect of volume content and aspect ratio of carbon fiber on thermal conductivity. This figure should be compared with Figure 15.17 to see that, unlike electric conductivity which does depend on the aspect ratio of the carbon fiber, the thermal conductivity is only dependent on fiber concentration and increases as it increases. 

Whereas selected unsaturated polymers can be made conductive, making saturated polymers like polyethylene or polypropylene conductive is another matter. Because of their low cost, availability and ease of processing, they are used as electrical insulators, and making them electrically conductive would seem at first thought difficult to do. In one approach, saturated polymers can be made conductive via polyacetylene chemistry by forming composites wherein the conductive phase can be varied in weight percent from 10 to 50 percent (4 - ). 

A large diffusion may be found also for composite materials, carbon, or metal based. In the first case different types of polymeric resins (thermoplastics, such as polypropylene, polyethylene, and PVDF, or thermosettings, such as epoxies and phenolics) are filled with carbonaceous powders (graphite or carbon blacks), to provide a material characterized by very high chemical stability in the fuel cell environment and satisfactory properties of electrical conductivity, but which cannot offer sufficient robustness at thickness lower than 2 mm. The metal composite plates are essentially based on combinations (sandwiches of different layers) of stainless steel, porous graphite, and polycarbonates, with the aim to exploit the characteristics of different materials. Their fabrication can be more complex but this is compensated by the possibility to incorporate other functional components, such as manifolds, seals, and cooling layers. 

PPy may be similarly coated on low-density polyethylene (LDPE), whereas grafting of the LPDE surface with acrylic acid enhances film growth and adhesion.86 The in situ oxidation of pyrrole by Fe(III) can also be used to deposit PPy films on polystyrene substrates.87 In a variation of this method, polyimide films exhaustively soaked in pyrrole (with up to 14% monomer uptake) have been coated with PPy via oxidation with FeCl3 in acetonitrile solvent.88 The resultant material shows electrical conductivity of ca. 4 x 10 2 S cm-1. 

The RAI Research Corporation also offers a range of battery separators under the name of Permion (JL). These membranes are made by radiation grafting of a suitably active group onto an inert base film. The active groups include weak acids such as acrylic and substituted acrylic acid and stronger acidic groups such as sulfonated styrene. The base film can be Teflon R, polyethylene or polypropylene. They are thus not strictly perfluorinated membranes as is Nafion, but in chemical inertness and in many physical properties such as electrical conductivity and ion flux are useful as separators in batteries. 

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