Some parameters that govern the extrusion-spheronization process are the velocity, temperature, spheronizer load, and spheronizer time. The extrusion velocity is important because it governs the total output of the extrudate. The output will always be as high as possible since that would increase profit. However, an increase in the velocity can affect the quality of the pellet. The spheronizer velocity also affects the quality of the pellet. If the spheronizer velocity is too low, there will be no significant changes in the extrudate. However, if the velocity is too high, there will be a size reduction of the particles. In addition, hardness, roundness, porosity, bulk and tapped densities, friability, flow rate and surface structure of the pellets are dependent on the spheronizer velocity. The extrusion temperature is important because it determines if the water that was used for the preparation of spherical granules will evaporate. The final form of the pill should not contained any liquid or water; it should have been evaporated. As a result, the pellet can be stored for a longer period of time. The spheronizer load affects the yield amount of pellets. By increasing the spheronization velocity and using a low spheronizer load, the yield decreased. However, by extending the spheronization time and using a higher spheronizer load, the yield increased. In addition, mean diameter increases with an increasing spheronizer load. The last parameter is spheronizer time which has a significant influence on the quality of the pellets. With an extended spheronizer time, a narrower particle size distribution and a higher sphericity can be achieved. Thus, the most spherical pellets are achieved by using a large number of holes during extrusion, a high spheronizer speed and longer time of spheronization.
It can be concluded from the above equation that due to the logarithmic relationship, a slight increase in filler solubility can result in a large increase in the extrusion force for very soluble fillers. However, for insoluble fillers, there is such a small difference that it is negligible.
The above equation shows that an increase in the filler and the drug solubility will result in a reduction in the pellet fraction size.
The above equation proves a significant linear relationship between the pellet density and the filler and drug level. If the filler or drug level increases, then there is an increase in pellet density. However, the pellet density will decrease if there is a decrease in filler solubility. This is common due to the high density of the insoluble fillers.