Milling Process for Enhanced Powder Flowability and Homogeneity

In the intricate world of powder processing, milling stands as a foundational mechanical process specifically designed for the precise reduction of primary particle size. At Munit, we define milling as the targeted operation to achieve a Particle Size Distribution (PSD) with a D90 typically ranging between 50 and 200 microns. This meticulous control ensures that the milled powder maintains excellent flowability, differentiating it from micronised powders which often exhibit increased stickiness and higher electrostatic charge. Consequently, milled powder, characterised by its coarser and tighter particle size distribution compared to micronized or crude crystalline powder, is exceptionally well-suited for critical applications such as direct compression, capsule filling, and various other oral dosage forms. Furthermore, this process is ideal for minimising the formation of ultra-fine particles while effectively reducing the D90 below 100 microns where required.

Our mechanical milling solutions incorporate a range of advanced impact mills, including hammer, blade, and pin mills, all engineered to utilise high-speed rotation to precisely impact and reduce the size of primary particles. A key feature of most of our mills is the integration of a grid with precisely defined diameter holes. This intelligent design ensures that coarser particles remain within the milling chamber for further crushing until they achieve the desired size, while simultaneously allowing particles of the correct dimension to exit the mill, preventing undesirable over-reduction.

The milling process, as employed by Munit, is optimally suited for applications where the primary objective is not to enhance the dissolution rate or bioavailability of the compound. For scenarios demanding improved bioavailability, target PSDs typically require a D90 below 10 microns, or in some instances, even below 5 microns – a domain usually addressed by our micronization capabilities. Milling, therefore, excels in preparing powders for robust and efficient downstream processing.

A critical aspect of mechanical milling, due to the high-speed rotation of internal components, is the friction-induced temperature increase within the mill chamber. This phenomenon necessitates stringent temperature management, especially when processing heat-sensitive substances. At Munit, we implement sophisticated temperature control measures, including the strategic ventilation of the milling chamber with inert gases like Nitrogen. Our capabilities extend to precisely controlling the gas temperature and meticulously measuring it both before and after it enters the mill chamber. This comprehensive control system provides complete oversight of the process’s impact on the milled powder, guaranteeing product integrity and consistency.