Dynamic relaxation time measuring system for powders and liquids

Abstract

With the increasing industrial use of electrostatic systems to coat surfaces, the relaxation time constants of the powder which is being applied electrostatically is a key intrinsic property of the coating material. The measuring system described involves: a powder compacting unit with a vibrator, a high-voltage power supply for corona charging, and an electric flux-decay-versus-time monitoring electrometer. The system allows evaluation of a realistic relaxation time constant, particularly for packed powder, from various levels of charge. To substantiate the operation of the system, tests results are presented for sugar, polyethylene, Arizona road dust as well as for a liquid dielectric transformer oil.<>