Comparative Study of the Triboelectric Charging Behavior of Powders Using a Nonintrusive Approach

Abstract

Powder processing operations such as blending or pneumatic transport can potentially induce triboelectric charging with subsequent agglomeration. Traditionally the charging behavior is investigated using a Faraday cage. In this paper, an alternative nonintrusive probe connected to a voltmeter for comparative triboelectric charging studies of sieved pharmaceutically relevant materials such as α-lactose monohydrate (ALM) and adipic acid (AA) on acetal surfaces under controlled environmental conditions was explored. The probe was verified using standard voltages with determination in the positioning limits for effective measurements between probe and surface. Results obtained with the probe were found to be in good agreement with the Faraday cage method. A greater incidence of particle-to-wall adhesions in smaller sized AA particles led to a reduction in initial surface specific potential while the higher quantity of fines in the ALM larger sieve fractions could be the major contributing factor in the reduced surface specific potential.

A review of factors affecting electrostatic charging of pharmaceuticals and adhesive mixtures for inhalation

“…This agreed with previous studies carried out by (Carter et al, 1992), (Eilbeck et al, 2000(Eilbeck et al, , 1999 and (Kwek et al, 2012) who showed the netcharge of lactose to increase with decreasing particle size. This could be explained as the specific surface area (per unit mass) increases with decreasing particle diameter and this makes a higher netcharge-to-surface ratio (net-CSR) for smaller particles obvious.…”

Novel Coupling of a Capacitive Probe with a Dynamic Vapor Sorption (DVS) Instrument for the Electrostatic Measurements of Powders

“…6 is comparable to values obtained previously by Kwek et al 6 which ranged from 4.7 % to 32.7 % using a similar approach. For other techniques values in the range of 40-50 % up to 100 % have been reported.…”

“…6 However, preliminary tests with the coupled system revealed that a large number of factors may affect the overall electrostatic field and therefore calibration and optimisation are required.…”

“…The same configuration on a bench-top setup has been previously used by Kwek et al. 6 The DVS cell surrounding the sensor is made of brass in order to provide shielding from external electric fields. The brass cell and hanging wire are grounded, whereas the sample holder is isolated via a polyvinylidene fluoride (PVDF) hook.…”

“…This signal drop is more pronounced compared to results found by Kwek et al as a high resolution, more sensitive probe is used for this method. 6 The optimum separation between the sensor and the test surface is 3 mm (± 0.5 mm) and the probe was set in a fixed position throughout all measurements. Furthermore, in order to load a sample, the DVS cell has to be opened which results in the sensor being moved away from the test surface.…”