Conductivity of polymers

Conductivities of polymers of technological interest such as polypyrrole and polythiophene are typically 1000 cm in the doped state, and the conductivity can be tuned by reversibly doping and undoping the polymer. Derivatives of these and other polymers have achieved even higher conductivities. 

Polymers. Ion implantation of polymers has resulted in substantial increases of electrical conductivity (140), surface hardness (141), and surface texturing (142). A four to five order of magnitude increase in the conductivity of polymers after implantation with 2 MeV Ar ions at dose levels ranging from 10 -10 ions/cm has been observed (140). The hardness of polycarbonate was increased to that of steel (141) when using 1 MeV Ar at dose levels between 10 -10 ions/cm. Conductivity, oxidation, and chemical resistance were also improved. Improvements in the adhesion of metallizations to Kapton and Teflon after implantation with argon has been noted (142). 

Even the simplest A -substituted pyrrole, A -methylpyrrole, electropolymerizes much slower than pyrrole itself Furthermore, the conductivity of polymers... 

The associated temperature profiles are shown in Figures 10 through 12. Metal in contact with Dowtherm is at 240°C, whereas in the middle of the plate, the metal temperature ranges from 226 to 234°C. Because of this effect, as well as the relatively low thermal conductivity of polymer melt, large temperature gradients exist along the y and z directions. At the walls the polymer temperature reaches 240°C, whereas at the center of the channel the polymer temperature is only 213°C, at the outlet. 

Polymeric conducting systems were also prepared by in situ polymerization of vinyl monomers in ionic liquids [22], with a conductivity of 1 mS/cm. A conductive polymer electrolytes were also prepared by polymerization in liquid EMIm(HF)nF leading to a composite poly(2-hydroxyethyl methacrylate)-EMIm(HF)nF. Recently, polymer electrolytes were prepared in the form of thin foils, by incorporating ionic liquids in a polymer matrix [13-15], Conductivities of polymer-IL or polymer-IL-solvent systems are collected in Table 4. 

Aneli J., Khananashvili L., Zaikov G. Structuring and Conductivity of Polymer Composites. Nova Science Publishers, Inc., N.-Y. 1998. 

Kilbride et al. (2002 Andriotis et al., 2003) measured the alternating current (ac) and direct current (dc) conductivities of polymer-SWCNT composite thin films such as PMPV and polyvinylalcohol (PVA), the result showed that the ac conductivity... 

CNTs can enhance the thermal properties of CNT-polymer nanocomposites. The reinforcing function is closely associated with the amount and alignment of CNTs in the composites. Well-dispersed and long-term stable carbon nanotubes/ polymer composites own higher modulus and better thermal property as well as better electronic conductivity (Valter et al., 2002 Biercuk et al., 2002). Both SWNT and MWNT can improve the thermal stability and thermal conductivity of polymer, the polymer-CNT composites can be used for fabricating resistant-heat materials. 

For most processing equipment, the low thermal conductivity of polymers strongly influences the overall heat transfer coefficient between the bulk of the polymer and the contacting metal surfaces, creating limitations in heat transfer rates. Heat transfer rates between processing equipment and the polymer depend on many factors, including thermal conductivity, machine clearances, and screw... 

Lobo, H. and Cohen, C., Measurement of Thermal Conductivity of Polymer Melts by the Line-Source Method, Polym. Eng. Set, 30, 65 (1990)... 

Watanabe, M., Yamada, S-L, and Ogata, N., Ionic conductivity of polymer electrolytes containing room temperature molten salts based on pyridinium halide and aluminium chloride, Electrochim. Acta, 40,2285,1995. 

Ogihara, W. et al., Ionic conductivity of polymer gels deriving from alkali metal ionic liquids and negatively charged polyelectrolytes, Electrochim. Acta, 49,1797,... 

As with other disordered materials, the thermal condnctivities of polymers are low due to phonon scattering. As a resnlt, even thongh polymers tend to have heat capacities of the same order of magnitude as metals (1.5 to 3.5 J/g K), their thermal conductivities (0.1 to 1.0 W/m K) are 1000 times lower than metals. Polymers, therefore, are generally good insulators, as long as their use temperature is below their thermal stability temperature. Few correlations for heat capacity and thermal conductivity of polymers... 

TABLE 6.1 Conductivities of polymer-metal salt complexes... 

The electric and heat conductivity of polymers may be increased by the incorporation of conductive fillers, such as aluminum flakes or metallic fibers. 

The e. s. r. and conductivity of polymers such as the polyacene/qui-none radical polymers (PAQR polymers), polyacetylenes and polybenzimidazoles have been investigated (59, 60, 61). The term eka conjugated has been coined to decribe their properties which are very similar to those previously described. The e. s. r. signal is without structure, the activation energy which ranges from 0.2—2.0 ev is considerably... 

The effect of impurities on the conductivity of polymers has not been investigated in great detail. Molecules which act as plasticizers invariably increase the conductivity and usually decrease the ac tivation energy of conduction. 

Balabanov, E. I., A. A. Berlin, V. P. Parini, V. L. Tal Roze, E. L. Franke-vich, and M. I. Cherkashina Electrical conductivity of polymers with conjugated double bonds. Dokl. Akad. Nauk. 134, 1123 (1960). 

Different SPM systems were developed to study the thermal properties. Thus a tiny thermocouple can be used to measure the heat flow from the surface and to test the local thermo conductivity of polymer surfaces [161]. Recently, a bimetallic cantilever has been used as temperature sensor to investigate phase transitions of n-alkanes with a heat sensitivity of 500 pj for a sample mass as low as to... 

However, there are, as always, complications both Tb and temperature effect is of importance the continuing plastic deformation results locally in high heat dissipation, which, due to the low heat conduction of polymers, is not transported to the environment. An estimation of the local temperature increase can be made with ... 

Compared to other materials such as metals, the thermal conductivity of polymers is 100 to 1000 times smaller (see Figure 8.5). Fillers increase the conduction by a factor of 3 to 4. 

Typical conductivity values of several polymers are shown in Fig. 1.1. The conductivity of polymers is compared with the conductivity of other solids in Fig. 1.2. It is seen that the maximum conductivity is quite high and close to that of good metals. 

Fig. 1.2. Conductivity of polymers varies over 16 orders of magnitude. Both experiments and theory suggest that ultimate conductivity will be larger than that of copper as shown by the dotted arrow [12,13].

The thermal conductivity of polymers is temperature-dependent. Fig. 17.2 shows a generalized curve as a function of T/Tg based on the available experimental data. According to Bicerano (2002) the results may be approximated by (the drawn lines in Fig. 17.2) ... 

It is interesting to compare the thermal conductivities of polymers with those of other materials. Fig. 17.5 gives a survey. 

Electrical conductivity of polymers is very low, making them very useful as insulation. 

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