Powder Electrostatics: Theory, Techniques and Applications

Abstract

Powder electrostatics remains an integral and challenging aspect of powder processing. During powder handling operations, such as particle size reduction, mixing and powder transfer processes, particles invariably develop electrostatic charge due to particle-particle and particle-surface interactions. Triboelectrification of powders is a complex phenomenon as most powders are organic crystals and behave as insulators under ambient conditions. However, it is generally accepted that charging occurs as a result of electron transfer between materials of different electrical properties. Factors influencing charging properties include particle size and shape, nature and work function of the contacting surface and the particulate material, area and frequency of contact, surface purity, and atmospheric conditions. Consequences of charge generation upon particle dynamics and powder behavior are often unpredictable. The standard method for measurement of electrostatic charge is the Faraday pail or well, with various application-specific modifications. Electrostatics, regarded by many as a nuisance and hazard, plays an important and ever emerging role in many industrial applications, including powder coating, xerography, and pharmaceutical processing.