Experimental characterization of triboelectric charging of polyethylene powders

Abstract

Triboelectric charging causes serious problems in the industrial processing of powders. We focus on the charging of polyethylene (PE) powder particles, whose agglomeration can cause serious economic problems in PE production in fluidized-bed reactors. The 'cascade method' apparatus, i.e., a slide followed by the Faraday's pail, was utilized to observe the particle-wall charging of PE particles in friction contact with various materials (glass, aluminium, PE) and allowed us to characterize the charging dynamics. Our results indicate that the evolution of the charge on the particles follows a saturation curve, where the saturated state is represented by maximum (outcome) charge. Such a trend can be conveniently fitted by a function representing the first-order dynamics. We determine the dependency of charging dynamics on various factors, e.g., the humidity, the slide surface roughness and the slide material. Our measurements imply that air humidity influences the charging process substantially more than the choice of the slide material. Moreover, we observe significant charging even in the case of the same materials being in contact. The work contributes to a better understanding of tribocharging and the estimation of charging-related parameters provides the input for the modelling of this complex process.