Electrical conductivity Volume resistivity

Electrical conductivity and resistivity [ISO 21318 for plastics Volume Resistivity ASTM D257, lEC 60093], dielectric [Dielectric Constant/ Dissipation Factor ASTM D150, lEC 60250 DIN 53483 EN 60811 Insulating materials Dielectric Strength ASTM D149, lEC 60243], etc,... 

Electrically conductive mbber (13) can be achieved by incorporation of conductive fillers, eg, use of carbon or metal powders. These mbbers exhibit volume resistivities as low as lO " H-cm. Apphcations include use in dissipation of static charge and in conductive bridging between dissimilar electronic materials under harsh operating conditions. 

Vulcani2ed mbber is an insulator (volume resistivity is 10 Q-cm), and the static generated by mbber tires created serious problems in vehicles until the introduction of electrically conductive carbon black as a reinforcing pigment. An excellent correlation was found between the potential generated and the resistivity of the tires (127,128) (see Rubber natural). 

See 2-3.1. Electrical conduction through solids takes place both through the bulk material and over the surface. In most cases surfaces have different physical and chemical properties than the bulk, for example due to contamination or moisture. Volume and surface resistivity can be separately measured for solid materials such as antistatic plastic sheet. Powders represent a special case since although both surface and bulk conduction occur, their contributions cannot be individually measured and the volume or bulk resistivity of a powder includes surface effects. 

The membranes also have a certain, though small ionic conductivity. The electrical resistance of membranes when referred to unit surface area is 10 to 10 Q-cm, which when allowing for the small membrane thickness (about 10 nm) corresponds to the rather high value of specific (volume) resistance of 10 to 10 Q-cm. 

Like electrical conductivity, the anode composition (i.e., Ni to YSZ volume ratio) also influences the anode activity or polarization. The lowest anode interfacial resistance is usually obtained when the Ni to YSZ volume ratio is 40 60. For example, Kawada et al. [42] found that anode interfacial resistance reached a minimum when the Ni content was 40 vol%, as shown in Figure 2.12. This was verified by several other independent studies [25, 31, 43, 44], For example, Koide [25] found that the... 

The bulk (or volume)-specific resistance is one of the most useful general electrical properties. Specific resistance is a physical quantity that may vary more than 10 in readily available materials. This unusually wide range of conductivity allows wide variety of electrical applications. Conductive materials, such as copper, have specific resistance values of about 10 fl-cm, whereas good insulators such as polytetrafluoroethylene and LDPE have values of about 10 fl-cm. Specific resistance is calculated from the following equation where R is the resistance in ohms, a is the pellet area in square centimeters, t is the pellet thickness in centimeter, and P is the specific resistance in ohm-centimeter ... 

The conductance value C is the flow volume through a piping element. The equation (1.11) could be thought of as Ohm s law for vacuum technology , in which qpy corresponds to current, Ap the voltage and C the electrical conductance value. Analogous to Ohm s law in the science of electricity, the resistance to flow... 

In summary, the volume resistivity of polyvinyl chloride plasticized by liquid or elastomeric plasticizers, or internally plasticized by copolymerization, was intermediate between the inherent volume resistivities of the pure components and combined the contributions of each of them. The presence of ionic soluble impurities in liquid plasticizers provided mobile ions which conducted electricity and thus lowered volume resistivity. Copolymerization with 2-ethylhexyl acrylate provided an excellent balance of softness and flexibility with high volume resistivity further studies of internal plasticization by copolymerization are therefore recommended. 

Because the surface of rubbers may conduct electricity more easily than the bulk of the material, it is usual to distinguish between volume resistivity and surface resistivity. Volume resistivity is defined as the electrical resistance between opposite faces of a unit cube, whereas surface resistivity is defined as the resistance between opposite sides of a square on the surface. Resistivity is occasionally called specific resistance. Insulation resistance is the resistance measured between any two particular electrodes on or in the rubber and, hence, is a function of both surface and volume resistivities and of the test piece geometry. Conductance and conductivity are simply the reciprocals of resistance and resistivity respectively. 

ASTM D991, 1989 (2000). Volume resistivity of electrically conductive and antistatic products. 

Standard test method for rubber property-volume resistivity of electrically conductive and antistatic products Specification for electrical properties of conducting and antistatic products made from flexible polymeric material... 

Most polymers are usually electrical insulators but need to be conductive for many engineering applications. Incorporation of conductive filler particles into the polymeric medium remains an interesting way to produce an electrically conducting polymer. Carbon materials provide electrical conduction and lead to a change in resistivity with increasing filler volume fraction in the polymer matrix. 

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