Electrical Behavior of Polymers

Most polymers are insulators. In fact, polyethylene and poly(vinyl chloride) are widely used as the insulating materials for electrical wiring, because they are highly insulating and weather resistant. However, to say a polymer is an insulator is a qualitative statement. To what extent does it conduct electricity Recently, families of conducting polymers were invented, resulting in the 2000 Nobel Prize in Chemistry. 

There are several basic relationships governing the electrical behavior of all materials. Ohm s law can be written 

These quantities can be used to describe the onset of molecular motion at the glass transition temperature see Section 8.3. In the present setting, we are interested in determining the electrical behavior of polymers. 

Two other quantities of interest are the resistivity, the resistance per unit distance, with units of Q/cm, and its inverse, conductivity, with units of Q Vcm or siemens per centimeter (S/cm). 

On the other end of the scale are the conducting and semiconducting polymers. Several types exist. For example, conducting fillers may be added, such as short metallic fibers that touch each other or carbon black. Alternately, an ionic polymer may be employed, or a salt may be added to the polymer. Conductivity in the latter systems depends on the moisture content of the polymer. 

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Pradhan, D.K., R. Choudhary, and B. Samantaray, Studies of structural, thermal and electrical behavior of polymer nanocomposite electrolytes. Express Polymer Letters, 2008. 2 630-638. 

ELECTRICAL BEHAVIOR OF POLYMERS 785 Table 14.6 Structures and conductivity of doped conjugated polymers (59)... 

Shiga, T., Deformation and viscoelastic behavior of polymer gels in an electric fields, Adv. Polym. Set, 134, 131, 1997. 

Shiga, T. Deformation and Viscoelastic Behavior of Polymer Gels in Electric Fields. Vol. 134, pp. 131-164. 

Deformation and Viscoelastic Behavior of Polymer Gels in Electric Fields... 

The electric properties of polymers are also related to their mechanical behavior. The dielectric constant and dielectric loss factor are analogous to the elastic compliance and mechanical loss factor. Electric resistivity is analogous to viscosity. Polar polymers, such as ionomers, possess permanent dipole moments. These polar materials are capable of storing... 

Additions of BN powder to epoxies, urethanes, silicones, and other polymers are ideal for potting compounds. BN increases the thermal conductivity and reduces thermal expansion and makes the composites electrically insulating while not abrading delicate electronic parts and interconnections. BN additions reduce surface and dynamic friction of rubber parts. In epoxy resins, or generally resins, it is used to adjust the electrical conductivity, dielectric loss behavior, and thermal conductivity, to create ideal thermal and electrical behavior of the materials [146]. 

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