Mechanism of Pellet Formation and Growth

Abstract

The strength of pellets depends, to a great extent, on the physical forces that bond the primary particles together. Attractive forces are short-range forces that cause solid particles to adhere to each other only if they are brought close enough together. Electrostatic forces are commonly encountered with fine powders, and are primarily produced during size reduction or due to interparticle friction. Magnetic forces, though they may not be encountered during the systematic development of drug pellets, could also be considered as bonding forces. Viscous binders and thin adsorption layers provide bonds that are based on immobile liquid bridges. Thin-adsorption layers are also immobile and can form strong bonds between adjacent particles by either smoothing out surface roughness and increasing the interparticle contact area or by decreasing the effective interparticle distance and allowing the intermolecular attractive forces to participate in the bonding mechanism.