Grinding media classification

Powders can be prepared from coarser pieces of material by grinding. Work 20A) gives an excellent list of references in relation to particle size measurement, grinding, classification, and collection. Schweyer (36G) discusses the effect of viscosity of the medium on the rate of grinding in pebble mills. 

Although the techniques in this section can be classified as methods that grind rubber under ambient conditions, this is for convenience rather than a precise scientific definition, because any mechanical action on rubber will result in it heating up above ambient due to a combination of the inherent hysteresis in the material and its poor conduction of heat. The classification of ambient is more to enable a distinction to be made between these types of processes and those where a medium (e.g., water or liquid nitrogen) is deliberately added to the process, or used in the process. 

---