The environment humidity effect on the tribo-charge of powder

Effect of humidity on contact electrification due to collision between spherical particles

“…12 Much work has investigated the effect of ambient RH once. 9,10,[13][14][15][16][17][18] However, existing studies significantly disagree about the effect of RH on CE: some results show that CE increases with increasing RH, 9 others show that CE decreases as RH is increased, [14][15][16][17] and more still state as RH increases, CE increases at lower RH, followed by decreases at higher RH. 18 In addition, the results of Refs.…”

Effect of Relative Humidity on the Electrostatic Charge Properties of Dry Powder Inhaler Aerosols

“…Under ambient temperature (22-C) and pressure (760 mmHg), the dielectric constant of air only increases by 0.017% if the RH increases from 15 to 90% (50). Rather, moisture adsorption on a powder is thought to be a major factor as it reduces interparticulate contacts and increases the particle surface conductivity, thus facilitating charge dissipation (29,(31)(32)(33). Moisture layers form on solid surfaces when the RH is above about 50% (51).…”

“…The improvement of surface conductivity of the particles through moisture adsorption is the major factor, but changes to bulk conductivity also occurs via water absorption at high humidities (32). Similarly, the time constant for charge relaxation decreases with increasing RH and amount of adsorbed water on the powder (33). Recently, it was found that RH had negligible effects on the charging of solids with low hygroscopicity, such as a-lactose monohydrate (34).…”

Investigation of Electrostatic Behavior of a Lactose Carrier for Dry Powder Inhalers

“…Thus, a greater change in RH was necessary before significant difference could be detected. An increase in ambient moisture level was reported to result in formation of a water film around the powder particles, facilitating relaxation or dissipation of static charge accumulated on particle surfaces (44)(45)(46). This could account for the lower initial charge of lactose at higher RH.…”

“…Increased ambient RH was often found to result in decrease in magnitude of electrostatic charge on the surfaces of various particles (10,11,13,18,34,46,52,53). Increased powder storage RH was also found to decrease the electrostatic charge of the powder upon aerosolization at an ambient RH of 45% (35).…”