粉粒体の凝集性(第5報)タッピングによる圧縮応力と粉末薬品の圧縮性

抄録

Relationship between porosity and compressive stress by tapping was investigated. The magnitude of tapping impacts was observed with vibration pickup and oscilloscope as the acceleration. The samples were packed loosely into a graduated cylinder and tapped with constant tapping height (△h) repeatedly until there was no decrease in apparent volume (Va) of the sample. The porosity obtained in this way was termed porosity of level-off state (ε_e). When no more change it Va was observed, the acceleration of samples becames identical to the acceleration of the tapping table. Consequently, compressive stress f and pressure p are given as, f=Ma and p=f/A, where α and M are the acceleration and mass of the samples, respectively, and A is the cross sectional area of a graduated cylinder. Measurement of εe under various acceleration conditions gave the relationship between f and ε_e. Applicability of the usual compression equations to tapping compaction was examined but no equation was applicable to tapping. The new relationship between α and ε_e was obtained as ε_e=k₁(1/a)+k₂, where k₁ and k₂ are constants k₂ is obtained by extrapolation of ε_e to α→∞ graphically, and signifies the closest packed porosity of the random packed powder bed. ε_e obtained by extrapolation of ε_e to α=1 is considered to mean the loosest packed porosity of the powder bed at the gravitational field. Both the closest and loosest porosity have not been obtained precise1y thus far.