Studies on Compression of Powders. II. : Discussion on Compression Process of Powders

In a first report, relaxation characteristics of powder itself were separated by analysing the stress relaxation phenomena during the compression process, and eliminating the relaxation due to the friction between powder and die wall. In this report, 14 steps of the pressure were applied in the range 100-4000 kg/cm2 and the variation of relaxation modulus (E2) to pressure was discussed. According to the observation, the relaxation modulus is greatly increased or decreased with the augmentation of pressure, especially in lower pressure range. The distibution curve of E2 value against the applied pressures and the compression curve were compared with hardness and relative density of the obtained tablet. As a result, it was suggested that pressure curve, hardness and relative density were closely related with increase or decrease of relaxation curve. From the results, it was considered that the compression process of powder is progressing, alternating two states, namely, the packing state and the structure fixed state.