PubMed · 4698999
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
C G Pitkin, A K Mitra. 1973. Flowmeter for pharmaceutical powders.. https://doi.org/10.1002/jps.2600620438
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Granules with a characteristic core-shell internal structure have been formed by in situ melt fluid-bed granulation, using d-mannitol primary solid particles and poly-ethylene glycol (PEG-6000) binder. The effect of binder particle size and binder/solids ratio on granule size distribution was systematically investigated. The mean granule size was found to be directly proportional to the binder particle size. The binder amount did not measurably affect the granule size, only the fraction of un-granulated fines. The microstructure of the granules was analysed by X-ray micro-tomography; the average shell thickness in the granules was found to depend on the binder/solids ratio, and the core volume was found to be directly proportional to the binder particle size. However, for binder particle size below a certain value the core-shell structure disappeared. A mathematical model based on a layering growth mechanism has been proposed and found to be consistent with experimental data. The proposed growth mechanism was confirmed by creating granules with bi-modal size distribution using a mixture of differently sized binder seeds.
Electrostatic interactions between particles can dramatically affect granular flows, creating industrial safety and handling problems [K. N. Palmer, (Chapman and Hall, London, 1973), pp. 388-389]. We present experimental data demonstrating that charging of grains can also cause spontaneous self-assembly that may generate lasting geological patterns under arid conditions. Paradoxically, we find that grains that tribocharge enough to produce small explosions, ejecting grains meters into the air, leave little net charge on grains. Rather, grains charge into strongly heterogeneous polar clusters. These assemble into stereotyped residual structures that resemble geological features, for example, razorbacks observed on Mars ["The Razorback Mystery," July 16, 2004, http://www.jpl.nasa.gov/missions/mer/images.cfm?id=701].
The aim of the present study was to investigate and compare granule and tablet properties of granules prepared by wet granulation in a rotary processor or a conventional fluid bed. For this purpose the working range of selected process variables was determined and a factorial study with 3 factors (equipment type, filler type, and liquid addition rate) and 1 covariate (fluidizing air flow rate) was performed. Two grades of calcium carbonate with different size and shape characteristics were applied, and the liquid addition and fluidizing air flow rates were investigated in the widest possible range. Dry mixtures of microcrystalline cellulose, polyvinyl povidone, calcium carbonate, and riboflavin, in a 10:5:84:1 ratio, were granulated in both types of equipment. The granulation end point was determined manually in the fluid bed and by torque measurements in the rotary processor. The filler type had a more pronounced effect on granular properties in the fluid bed, but the rotary processor showed a higher dependency on the investigated process variables. The rotary processor gave rise to more dense granules with better flow properties, but the fluid bed granules had slightly better compressional properties. Furthermore, the distribution of a low-dose drug was found to be more homogeneous in the rotary processor granules and tablets. Generally, wet granulation in a rotary processor was found to be a good alternative to conventional fluid bed granulation, especially when cohesive powders with poor flow properties or formulations with low drug content are to be granulated by a fluidizing air technique.