Packing dynamics of powders at high temperature

In industrial powder processing, precise control of environmental temperature is difficult especially for large production facilities. A better knowledge of powder behavior modification due to temperature variation will help to improve product quality and consistency. From a fundamental point of view, the effect of temperature on powder flow and packing dynamics is still poorly understood. In particular, because temperature modifies the complex interplay between the different forces acting at the contact between the grains. The packing dynamics of a set of different powders (lactose, cacao and dried milk powder) has been investigated with a tapping experiment. After the filling procedure, the sample is heated and the evolution of the density is measured after each tap. We show that the packing dynamics is drastically influenced even for low temperature changes. Slight increase of temperature affects both the packing kinematics and the packing range characterised by the classical Hausner ratio analysis. Finally, the different physical mechanisms that could explain these modifications are discussed. The results of this preliminary study demonstrate the importance of temperature in powder behaviour and strongly motivate further investigations.