Analysis of Wet Powder Characteristics using Fundamental Numerical Model of Pressure Transmission

In this study, compression test was applied to evaluate rheological characteristics of wet powder. Various quantities of moistened lactose monohydrate and microcrystalline cellulose were compressed in a cylinder. Relationships between compression transmission rate pT / P and dimensionless sample height H / D under various compression pressures P were fitted to a theoretical pressure transmission equation of pT / P ＝exp (-4μKH / D）. As a result, high correlations were obtained between them, indicating that pressure transmission of wet powder behaved as the ideal condition. The stress applied to the cylinder inner wall during the compression test was measured using strain gauges attached to the cylinder wall and friction coefficient of the wall surface μ and Rankine coefficient K were calculated. Consequently, the behaviors of μ and K under various compression pressures, liquid contents and liquid viscosities were investigated. From these results, it was suggested that the method proposed in this study could estimate a state of the wet powder under pressure.