Design and validation of an annular shear cell for pharmaceutical powder testing

An annular shear cell was constructed for powder flow testing, the influenc e of design and process parameters was characterized, and the results were compared with other flow methods. The shear cell was designed with intercha ngeable parts to mimic other sheer cells. The texture of the powder-metal i nterface and the gap distance between the lid and side wall of the trough w ere varied, and the effects of shear rate, powder bed thickness, and consol idation times were tested. Shear parameters, such as cohesion, angles of fr iction, and flow factors, were measured for microcrystalline cellulose, anh ydrous lactose, spray-dried lactose, mannitol, dibasic calcium phosphate di hydrate, anhydrous theophylline, and theophylline monohydrate powder. The r esults were then compared with the Carr index, mass flow rate, and flowabil ity index. Design parameters such as surface texture and the gap distance s ignificantly affected the shear call results, whereas for the process param eters studied, the shear rate? consolidation time, and powder bed height ha d a minimal effect on the shear cell results. Of the shear parameters obtai ned, the angles of friction best represented the known flow properties of p owders and were in general agreement with those from other flow tests (C) 2 001. Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm S ci 90:531-540, 2001.