Half-time electrostatic charge

Table 7.3. Half-time electrostatic charge decay of superficially charged materials...

The electrostatic charges accumulated on the surface of macromolecular compounds are very difficult to eliminate because of the very low electric conductance of these materials. This is measured by the half-time electrostatic charge decay this value is given for some polymeric materials in Table 7.3 [2]. Since most of these materials have an appreciable value for the half-time charge decay, charges accumulate on them when these materials are rubbed. 

The particle residence time in the charging section of an electrostatic precipitator is 0.6 s. What is the ion concentration such that one-half the maximum charge on the particles is reached diming this residence time ... 

Electrostatic attraction causes a continuous and rapid disappearance of the aerosol in plastic spacers, the aerosol half-life is typically 10 s, compared with 30 s if the static charge is abolished (24,37,38). Because of this short residence time in plastic spacers, the inhalation must be coordinated with actuation of the pMDI to obtain an optimal dose. This obviously negates one of the major advantages of spacers. 

In these expressions, me, Vc, Fd, F, X, a, H, t, 17, p, R, DLVO force, the hydrodynamic force, the scaled distance, the linear radius of the cells, the dimensionless closest half surface-to-surface distance between two cells, the scaled half separation distance between two cells, the time, the viscosity of liquid phase, the hydrodynamic retardation factor, the density of the cells, the gas constant, the scaled DLVO potential, the scaled van der Waals potential, and the Hamaker constant of the system, and i, , and I are dummy variables. Note that the fourth and fifth integral terms on the right-hand side of (25.141) represent, respectively, the contribution to the electrostatic repulsion force when the fixed positive and negative charge in the membrane phase of a cell appears. Equation (25.135) can be rewritten to become... 

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