Abstract
To compare the compaction behavior of potassium chloride and lactose powder of 42 to 65 mesh, they were compressed under the constant pressure of upper punch (about 1000 kg/cm2 in the maximum) by compaction apparatus with a cylindrical die (8.02 mm inside diameter), in which the powder of constant net volume (0.7545 cm3) was filled. During the compression continued for ten hours, the thickness of powder bed and the pressure transmitted to lower punch were measured. And then the replicated surfaces of compacts were observed by microscope so as to examine the packing structure. In the case of potassium chloride powder, under the lower pressure than the critical pressure which exists between 391 and 625 kg/cm2, particles seem to be deformed plastically in appearance. Under the higher pressure than the critical pressure, many fragments or cracks are produced and these small fragments move to fill up voids very closely, as if original particles were deformed plastically. Therefore the values of the porosity of powder bed and the ratio of lower to upper punch pressure approach to zero and 100%, respectively. In the case of lactose powder, as particles are brittle, they are fractured and small voids are filled with the fragments. The thickness and the ratio take the almost constant values after about five hours in spite of considerable amounts of void left still.
