Flow defects in wet powder mass extrusion.

Surface impairment, in the form of the flow defects roughness and sharkskinning, has been shown to occur with microcrystalline cellulose/lactose/water mixes on extrusion under varying process conditions. These defects result from the imbalance of stresses at the outer wall of the extrudate on leaving the die and can be avoided by changing the process conditions that are known to affect these stresses, e.g. the length of the die, the velocity of throughput and the moisture content of the formulation.