Formation of Multi-size Silica Particle Coating on Polyethylene Core by Rotational Dry Impact Blending

Composite particles are applied in various industrial fields. In order to prepare higher function composite particles, it is often required to coat core particles with multi-component particles. In this paper, coating of polyethylene core particles with fine silica particles was investigated with particular attention to the effect of feeding procedures of fine particles on the coating ratio. Three types of silica particles with different sizes were used as coating particles. The feeding procedures investigated were (1) simultaneous feeding of all fine particles at once, (2) three-step coating started from the feed of the smallest particles followed by larger particles and (3) three-step coating started from the feed of the largest particles followed by smaller particles. It was found in (1) simultaneous coating and (2) three-step coating started from the smallest particles that the smallest particles obstructed the coating with the other fine particles, leading to a reduction in coating ratio, Among the three procedures, (3) three-step coating started from the largest particles was advantageous for the formation of densely packed coating surface. However, even in (3) three-step coating started from the largest particles, the effect of obstruction of coating in the second step was observed. The effect of the obstruction can be explained by a packing model of triangular units.