Experimental study of triboelectric charging of polyethylene powders: Effect of humidity, impact velocity and temperature

Abstract

The manufacturing and handling of polyethylene (PE) powders is associated with undesired charging, resulting in agglomeration of charged particles, wall sheeting and eventually leading to plugging of reactors/conveyors. In this work, we measured the triboelectric charging of PE powders using both sliding and shaking apparatuses in dependence on humidity, impact velocity of colliding particles and temperature of the colliding particles or of the wall. As expected, saturation charge of PE particles is reduced with increasing air humidity. However, in a more detailed study we observed that whenever we change the humidity, the saturation charge rapidly reaches the equilibrium value and no hysteresis in charging that might be caused, for example, by adsorption/desorption thermodynamics is observed. Saturation charge is believed to be independent of impact velocity; however, we show that the saturation charge is proportional to impact velocity in the system of PE particles of non-spherical shape. The charging is more pronounced as the temperature of PE particles increases, however, it is unchanged if only the metal wall in contact with the particles is heated. That is a different trend than observed for spherical metal particles (Greason, 2000).