Measuring electrostatic charging of powders on-line during surface adhesion

Electrostatic charging of powders and powder mixtures were measured on-line during surface adhesion by sliding the powders in a pipe. The cumulative charge was monitored as a function of transferred powder mass. The effect of adhesion on the charging was assessed by observing the slope of the measured curve at the very beginning of the measurement. Due to adhesion, the charging decreased exponentially. For mixtures, the powder with higher concentration initially dominated the charging. The sign of the charge changed as the additive powder started to adhere, indicating that contacts between the two dissimilar powders started to govern the charging.