By Aveka Inc
Hammer milling uses rapidly rotating “hammers” to collide with the material once it is fed into the chamber. The particles are then struck repeatedly until they are reduced to the desired size and can pass through a screen. Hammer mills can use either “hard” or “soft” hammers: - Hard hammers are blunt and impact the material with a flat surface, leading to greater particle size reduction and wider particle size distribution. - Soft hammers use sharp, knife-like edges to slice apart the material, which achieves less particle size reduction, but a narrower particle size distribution. The biggest potential drawback to using a hammer mill is when the material itself is not intrinsically friable, meaning it won’t easily crack under the application of force. Intrinsically friable materials usually have microscopic defects, like fractures or gaps, which act as natural places along which cracks can propagate, allowing the material to break apart. There are generally 3 options for making the polymer pellets more friable (combinations of the below processes generally work synergistically): 1. Solvent crazing: Produces a network of fine cracks on the surface of the pellets from which cracks can propagate. 2. Sample irradiation: Exposes the pellets to doses of ionizing energy to introduce defects that affect mechanical strength. 3. Cryogenic freezing: Reduces the temperature of a polymer to below its glass transition temperature (T g), which makes the polymer brittle. AVEKA is a full-service toll processing and research & development company that specializes in hammer milling and other particle reduction processes. From lab-scale to production and with over 30 unit operations, we can handle your one-step or multi-step manufacturing needs.
