Static Electrification of Solids

The phenomena of the electrification of solids are complex. In gas-solid flows, surface contact by collisions, ion collection, and thermionic emission are known to be the major modes of particle electrification. Details of these three charging modes are introduced in the discussion that follows. 

Gauss s law states that if an imaginary enclosed surface of area S is drawn around a uniform density of charge, the component of the electric field at the surface, which is perpendicular to the surface, is proportional to the total charge enclosed. Hence, Gauss s law is expressed as 

Source J. A. Cross Electrostatics Principles, Problems and Applications, Adam Hilger, 1987. 

The work function, W, is defined as the work required to remove an electron out of a metal material from the top of the energy distribution. The work function is related to the potential function / , known as the thermionic work function, by 

An intrinsic potential difference exists between dissimilar dry metals in contact. This potential difference, known as the Volta potential or the contact potential, can be related to the work functions of the two dissimilar materials A and B as 

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M7. Montgomery, D. J., Static electrification of solids, Solid State Rhys. 9, 139 (1959). 

Static Charge Development. Static electrification of solids can occur in various ways. Different operations will produce the percentages of the theoretical maximum charge density shown in Fig. 3.7.33... 

Figure 6-1 Interaction between solid-state physics and static electrification of solids (Krupp, 1971). Reproduced with permission of The Institute of Physics.

Bauser, H. Static electrification of organic solids, Dechema Monograph (Frankfurt Verlag Chemie) 72 11-29 (1974)... 

Harper, W. R., How do solid surfaces become charged , in Static Electrification. Proceedings of Conference, Conf. Series No. 4, The Institute of Physics and the Physical Society Static Electrification Group, London, May 1967, pp. 3-10. Harper, W. R., Contact and Frictional Electrification, Oxford university Press, 1967. 

Pressure sensitive adhesives are an exception to what was stated in the very first paragraph of this article, in that they do not harden to a cohesively strong solid. They are in fact viscous liquids, and remain so when incorporated in an adhesive joint. Nevertheless, it is essential that they adhere to substrates, and they will do so by one or more of the mechanisms which have been already described. Physical adsorption will contribute in every case, and in most cases it may be the only mechanism, but chemical bonding via ion-pairs may contribute if the adhesive contains carboxylic acid groups and the substrate is a metal. Static electrification is another possible contributor. 

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