粉粒体の凝集性(第2報)粒径の影響

概要

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Influence of particle size on apparent cohesiveness (α_c) and cohesive force per particle (f_C) at the loosest packing state of the powder beds was investigated. Experiments utilizing the method reported in the previous paper were made under about 50% R.H. with five different samples. The values of α_c decrease with increase of particle size (Dp) and fc increase with Dp. Unexpected large cohesive forces were observed in large particles. To elucidate these facts, simple model of leaning between particles at the surface of a powder bed were assumed, and unit leaning force Lu was derived as Lu=w/2,where w is the mean weight of a particle. If f_L is the cohesive force due to leaning between particles, the leaning efficiency (P) is defined as f_L=k・P・Lu, where k is the number of contact points. In large particles, the values of f_L is considered to be the same as fc since the cohesive force due to adhesion between particles (f_A) will be negligible. From these relations, the value of about 0.11 for P was estimated experimentally. Leaning probability (p) is represented by P=Σ^^m__<r=1>p^r, and from this equation, it becomes clear that p takes the value of from 0.11 to 0.10 when the values of P and m take the values of 0.11 and 1 to infinite. The cohesive force of adhesive type(f_A)was calculated from f_A=f_C-f_L, and particle size dependancy of f_A was discussed.
公益社団法人日本薬学会の論文
1972-11-25