The influence of initial packing on the compression of powders.

The influence of the initial packing density on the compression properties of lactose and sodium chloride has been studied. Differences in initial packing density are eliminated for both materials at relatively low pressures. The results have been analysed by the equations of Kawakita (1956), Heckel (1961), and Cooper & Eaton (1962). The constants derived from the Cooper & Eaton equation are dependent on the choice of low pressure data. The Kawakita constants are influenced by the initial packing of the powder. The Heckel treatment uses data at pressures above the point where the initial packing exerts an influence. Hence the constants are independent of the initial packing. If comparisons are to be made between processing treatments or mixtures which change the initial packing of the powder, the Heckel equation would appear to offer the most valid approach.