ANALYSIS OF EXTRUSION OF SOME WET POWDER MASSES USED IN EXTRUSION SPHERONISATION/

The extrusion how behaviour of mixtures of lactose, microcrystalline c ellulose (MCC) and water in the ratio 5:5:6 by weight has been analyse d from data previously obtained by a ram extruder for powder and collo idal grades of MCC. The analysis followed a recent approach of examini ng the viscous and elastic behaviour of polymers. Results suggest that at low how rates, mixtures containing colloidal grades of MCC have si gnificantly higher shear viscosities than powder grades. The present a nalysis also shows that shear thickening of some mixtures occurs. Elon gational how was also examined together with entry flow to the die. Th e results of the analysis indicate that: (a) particle size of the MCC is not important, (b) the greatest extrudate distortions occur for sys tems having relatively low shear viscosities at low flow rates. There appears to be an optimal elasticity for the formation of satisfactory spheres in the spheronisation stage, i.e. they must neither be too ela stic nor have low elasticity.