Triboelectric effect on the adhesive coating of particles in a high shear mixer

Adhesive dry powder coating is widely applied in pharmaceutical and particulate processing. Achieving a uniform distribution of fines of active pharmaceutical ingredient (API) on carrier surfaces remains challenging due to complex particle-particle and particle-wall interactions. This study employs the discrete element method (DEM) coupled with a triboelectrification model to investigate the dynamics and electrification mechanisms governing adhesive mixing in a high-shear mixer. The particle motion, charge evolution, and their combined influence on coating performance are analysed. Results show that while electrostatic forces have minimal impact on particle velocity and power draw, they exert a pronounced effect on mesoscale mixing behaviour. Bipolar charging among carriers leads to strong spatial heterogeneity, causing fines to concentrate locally and substantially reducing coating uniformity. Modifying the impeller and vessel surfaces using materials with work functions closer to that of fines causes favourable charge transfer and enhances coating uniformity. On the other hand, increasing the impeller rotational speed increases the specific charge level of fines, intensifies charge-driven segregation, and results in less uniform API attachment. The study highlights the critical role of electrostatics in adhesive mixing and demonstrates how controlling wall work function and rotational speed can significantly improve mixture homogeneity.