(680g) Characterizing the Effect of Powder Flow Aid Additives

We show the effect of the addition of a small fraction of flow aid agents on the flow of cohesive powders. In particular, we will focus on mesoporous silica (MPS) grains playing a role on both capillary and electrostatic forces. We will compare the effect of MPS grains with the addition of magnesium stearate and other classical flow aid agents. The effect on the flow is quantified with the rotating drum method (GranuDrum instrument). According to both grain and pore size of MPS, the cohesiveness decrease can be immediate (for small MPS grains having small pore size) or on the longer term (for larger MPS grains having higher pore size). The effect on the powder electrostatic properties is analysed with a recently developed powder tribo-electrometer called GranuCharge. The quantity of electrostatic charges created during a flow in contact with stainless steel is decreased by the presence of MPS grains. We show that this decrease is induced by a modification of electric resistivity. The MPS grains are adsorbing the humidity contained in the powder and are forming a network having a low resistivity, improving the diffusion of electrostatic charges.