Effects of Electrostatic Charges

The presence of an electrostatic field subjects a material to a stress. Such fields can arise from the presence of free charges in the material or from the action of an external field. A number of authors (Hogan, H12, H13 Graf, G8 Doyle, Moffett, and Vonnegut, D6 and others) give the outward pressure on a liquid sphere with a uniformly distributed surface charge as 

For comparison, the constraining pressure due to surface tension, a, is given by 

The effect of electric charge on the vapor pressure of a liquid is given by the classic equation of Thomson as quoted by Gallily and Ailam (Gl) and Vonnegut, Moffett, Sliney, and Doyle (V3) 

From the illustrative value given for pe above it is apparent that electrostatic effects on vapor pressure will be negligible unless the particle charge level is orders of magnitude greater than I V/micron. 

There is also the possibility of having surface tension affected directly by the presence of an electrostatic field. To some extent this will be a matter of definition since the outward pressure due to a surface charge could be defined as an apparent effect on surface tension. Hurd, Schmid, and Snavely (H15) measured the surface tension of water and water solutions when fields up to 0.7 V/micron were applied across the air-solution interface. The results showed a reduction in surface tension of less than 1 %. These data must not be considered conclusive, however, because insufficient details are reported to permit assessment of the exact nature of the electrostatic field applied or of the validity of a number of corrections that had to be applied but were reported to be very large and difficult to apply. 

---

The effect of surface electrostatic charge on a material on the attachment of the decay products of radon has been known since pioneering work on atomic structure by Rutherford. Extensive research into this area for the radon and thoron progeny has been conducted in this laboratory for environmental monitoring purposes. Several authors have reported on the effect of electrostatic charge on the collecting characteristics of copper for the radon progeny for exploration purposes (Card and Bell, 1979). 

No attempt has been made in this chapter to cover the biological or medical effects of electrostatic charges. It should be noted, however, that Gordieyeff (G6) gives a bibliography of forty-two references, a large number of which deal with the medical aspects. 

Singh MP, Stefko J, Lumpkin JA, and Rosenblatt J. The effect of electrostatic charge interactions on release rates of gentamicin from collagen matrices. Pharm. Res. 1995 12(8) 1205-1210. 

Wildhaber, J.H. Devadason, S.G. Eber, E. Hayden, M.J. Everard, M.L. Summers, Q.A. LeSouef, P.N. Effect of electrostatic charge, flow, delay and multiple actuations on the in vitro delivery of salbutamol from different small volume spacers for infants. Thorax 1996, 51, 985-988. 

E. Effects of Electrostatic Charges of Surfactants and Cosurfactants on Reversed Micellar Properties... 

Anhoj J, Bisgaard H, Lipworth BJ. Effect of electrostatic charge in plastic spacers on the lung delivery of HFA-salbutamol in children. Br J Chn Pharmacol 1999 47 333-336. 

Figure 2 Effect of electrostatics charging on the pressure drop behavior of PVC particles in 0.0254 m (I.D.) system-Wj = 1.14kg/min.

---