Effect of Surface Characteristics of Particle on the Adhesion Property of Powders

(Institute for Chemical Research, Kyoto University)

Abstract

The adhesive property of powder is known to be very variable and also to be affected by the surface condition of the particle. In this experiment, the relation between the surface states of par ticles and the adhesive property of powders has been studied. The white alundum, calcium carbonate and kaolin clay were used as sample powders. The surface condition of white alundum and calcium carbonate were varied by adsorption of capric acid or sodium stearate, and kaolin clay were heat-treated. The adhesive property has been measured by final packing density ρf and coe fficient K₁ in Kunos^' equation at the first stage of packing or cons tant b in Kawakitas' equation by the same tapping compress method. The attraction force between the particles at the contact point were measured by shearing test of powder bed.
The results obtained are summarized as follows:
The effect of surface adsorbed layer of capric acid on white alundum is very small compared with the influence of the particle size. But the treatment of calcium carbonate by sodium stearate is effective, and especially the packing density is affected largely, at humid atmosphere.
The effbct of this distinction of surface treatment upon both the powders is presumed to be due to the difference of mechanism of surface adsorption.
The adhesive property of kaolin clay when heattreated, has changed remarkably at the fall of temperature of the crystal structure. The observed variation of the adhesive property has been compared with the reduction of the surface active site.
The adhesive force at the contact point between the particles is not influenced by the surface adsorption layer on the white alundum.