FLOW PROPERTIES OF SELECTED PHARMACEUTICAL POWDERS FROM A VIBRATING SPATULA

Studies have been performed to characterize the flow of certain powder s of pharmaceutical interest from a vibrating spatula. Lactose, cromol yn sodium, sodium chloride and charcoal powders were prepared by milli ng or sieving. Jet milling yielded micronized powder (1-10 mum), which was recovered from the product jar or metal cyclone. Particles in the larger size ranges were prepared by sieving. Photomicrograph images o f the products were obtained by scanning electron microscopy. All of t he powders were subjected to flow studies from vibrating beds to a top loading pan balance. Cumulative mass versus time, flow profiles were plotted. Bulk flow properties, as reflected in mass flow rates (M(i)), were assessed. Irregular flow patterns were obtained for lactose, cro molyn sodium and charcoal, whereas sodium chloride was free flowing. T he lengths of the lines depicting cumulative mass versus time, for sam ples of each material, were estimated using the inswing structured wal k technique. Stride lengths (lambda) of 1-100 mm were employed. Fracta l dimensions were obtained from graphs of the logarithm of the cumulat ive mass versus time line length plotted against the logarithm of the stride length. Thus, flow irregularities were indicated by fractal dim ensions (delta). In all of the powders studied, mass flow rates increa sed as the particle size increased. Sodium chloride did not exhibit fr actal behavior (delta less-than-or-equal-to 1.007), as there were no f low irregularities. Lactose, cromolyn sodium and charcoal did not appe ar to exhibit fractal behavior (delta less-than-or-equal-to 1.010) at large stride lengths (lambda = 15-100 mm). At small stride lengths (la mbda = 1-10 mm) these materials did exhibit fractal behavior (delta = 1.029-1.059) indicative of flow irregularity. This method may be used to numerically quantify uniformity of flow from a vibrating spatula, a nd would be useful in a number of industrial processes.