Effect of contamination of pharmaceutical equipment on powder triboelectrification.

Triboelectrification of pharmaceutical powders may cause problems during processing and manufacture due to adhesion/cohesion effects. The aim of this work was to investigate the role of adhered particles and moisture as contact surface contaminants on the electrostatic charging of size fractionated lactose, following contact with a surface, i.e. stainless steel, typically used in pharmaceutical process and manufacturing operations. Replicated experimental runs without cleaning the contact surface showed a successive decrease in the net electronegative charge due to adhered lactose particles. Removal of these contaminating particles by different cleaning methods had a considerable effect on the charge after triboelectrification. The charge on the lactose samples was found to decrease when humidity in the cyclone apparatus was increased from 2 to 100% relative humidity. These results clearly demonstrate that moisture, particulate contamination and method of cleaning of processing equipment during pharmaceutical manufacturing operations may influence the electrostatic behaviour of powders.