Physical properties of pharmaceutical pellets

A series of various methods were applied to characterize samples of pharmaceutical pellets. Fourteen pellet types were tested to obtain the coefficient of restitution, coefficient of friction, stiffness, flowability, and distribution of size, shape, and density. An atomic force microscope was used to determine the pellet surface properties. The values obtained for the coefficient of restitution ranged from 0.568 to 0.843, and a sample-specific dependence of impact velocity was demonstrated. Mean pellet size was between 807.2 and 1271 μm, granular density ranged between 1.086 and 1.483 g/ml, and the coefficient of friction was around 0.21 for pellet–steel contact and around 0.16 for pellet–glass contact. AFM provided information about surface stiffness and roughness; furthermore, the values obtained correlated well with the results of other methods. The values of Young’s modulus of the pellets using the plate compression method or AFM surface testing were close to 1 GPa. The database of properties of commercially available sample pellets presented here represents a solid foundation for sound CFD and DEM simulations of pharmaceutical processes connected with the production of dosage forms comprising pellets.

► We tested 14 samples of pharmaceutical pellets.
► Coefficient of restitution and friction, density, size, and hardness was evaluated.
► We used AFM for analysis of surface stiffness and roughness.
► Most pellets showed velocity dependent coefficient of restitution.