Milling causes triboelectrification of particles as the particles frequently make contact with each other and with the walls of the milling equipment, causing triboelectrification. Tribo-electrification refers to a process whereby two materials come into contact with one and are subsequently charged. Pharmaceutical powders are often smaller in particle size (less than 100 µm) and irregularly shaped with a low bulk density. They are prone to electrostatic charging because they normally have a high electrical resistance, preventing charge dissipation (Grosvenor and Staniforth, 1996). The behaviour of the materials after tribocharging may change, causing the materials to adhere to one and other or repel each other.Most pharmaceutical powders are inevitably charged when undergoing the process of manufacturing because of their inter-particle and particle collisions. An attractive of repulsive electrostatic forces usually results from the electrostatic charges of both positive and negative polarities. Consequently, electrostatic charging may result to segregation or agglomeration of particles in the course of powder transport, dispersion, and other usage processes. A number of studies have established that charged particles may cause contamination of tools since charged particles stick to the inner surfaces. The contaminating elements cause considerable impact on the charging process of powder and hence establish differences in charging in the course of the processing.The process of milling is usually applied in pharmaceutical manufacturing for reducing size of particles since crystallization alone cannot achieve a desirable and narrow particle size. However, milling causes generation of thermodynamically unbalanced and amorphous areas on the particles’ surfaces, which go through re-crystallisation when pharmaceutical drugs are stored. This degeneration impacts on the physiochemical properties of Active Pharmaceutical Ingredients (APIs) including physical stability, solubility, flow properties and aerosolisation characteristics, which causes significant impact on the performance of the drug product.In the process of therapeutically assembling granular solids into tablets, pharmaceutical industries undertake various manufacturing processes. Among these would be milling, which has been considered as a size reduction process that involves application of various forces on particles to produce the required pharmaceutical particulates using various
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