Triboelectrification

Triboelectric Series. Prediction of triboelectric behavior in granular solids is hampered by difficult-to-control factors such as particle shape, prior mechanical contacts, material purity, and particle moisture content (which is usually related to airborne humidity). In the absence of any reliable predictive model for powder electrification, the practical requirements of industry necessitate an empirical approach (Taylor and Seeker, 

Limits on Particle Charging. The electrical charge carried by a particle resides on the surface. Thus, a fundamental upper limit for particle electrification may be computed by imposing the constraint that the electric field at the surface can not exceed the dielectric strength of dry air, Eb 30 kV/cm. According to this hypothesis, the upper limit upon surface charge density becomes 

Conspicuous by its absence from Table 2 is charging data for fluidized beds. There are several reasons forthis omission. First, fluidization 

The usual prescription for controlling triboelectrification in pneumatic transport is to limit the flow rate, but this solution conflicts with the tendency to increase plant production levels. One alternate proposal for the control of tribocharging is to exploit the so-called dense-phase transport mode (G. Butters, 1985) however, there seems to be some dispute about the efficacy ofthis scheme (Konrad, 1986). 

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In the field of toner materials, the emphasis in the 1990s is on increasing developer life, particularly using color toners. The life of a typical black two-component developer is about 80—100 kilocycles per kilogram, whereas for color toners it is only about 10 kilocycles per kilogram (64). Also, there is a need for better control of triboelectrification of toner particles that would not only allow stable operation under all environmental conditions but also provide consistent, fast, and reproducible contact charging. 

Ill the case of a toner particle, the charge q on the particle was produced by triboelectrification. As such, it is fair to assume that the charge is uniformly distributed and proportional to the surface area, with a proportionality constant attraction between the particle and the substrate is obtained using the method of images, discussed previously. Accordingly,... 

Triboelectrification. In triboelectrification, plastics are brought into repeated contact resulting in a loss or gain electrons depending on the relative dielectric constant of the materials (125). In the case of ABS and HIPS, ABS exhibits the higher dielectric constant. Therefore ABS should become positively charged. Once materials have been... 

The separation by triboelectrification relies on a difference in the dielectric constant of the material to be separated. When noncon-ductive materials are brought in close contact, a net electric charge is left on the material, either positive of negative, depending on the difference in the dielectric constant of the materials. ABS has a... 

An aerosol is a dispersion of discrete particles in a stream of gas. Starch and cellulose aerosols are potential fire hazards in granaries where friction between the moving, micronized particles causes electrification, whereupon separate accumulations of positive and negative charges may discharge as an electric spark and ignite the combustible solute (contact electrification synonymous with triboelectrification Ross and Morrison, 1988). 

The charges generated from triboelectrification often lead to problems in industrial processing. The accumulation of charges in a silo during powder loading may... 

Eilbeck, J. Rowley, G. Carter, P.A. Fletcher, E.J. Effect of materials of construction of pharmaceutical processing equipment and drug devices on the triboelectrification of size-fractionated lactose. Pharm. Pharmacol. Commun. 1999, 5, 429 33. 

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