This investigation was carried out by use of the ring shear cell for various kinds of inorganic and organic powders.
Relationship between shear stress τ and normal stress σ fitted well with the equation of yield locus. Each parameters, flowability index n, tensile strength T, cohesive force C was calculated by the computer analysis using χ²-distribution minimum method.
It was found that this method was superior to the single plane shear box method in the reproducibility. However, shear stress measured by this method showed lower value than that by the single plane box method in the range of the same higher normal stress.

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This report describes the low temperature Powdering system of plastic materials using liquid nitrogen, which has been developed by the authors in Nippon Sanso K.K. (Japan Oxygen Co., Ltd.) since 1972.
It is shown that this system can be applied to Powdering several thermoplastic materials and others, which are otherwise very difficult to be made into powder state, especially in atmospheric condition. With this system, these plastics can easily be fine powders, for instance, of 100μ.
Because of the advantages of using liquid nitrogen, for instance non exidizing and non explosive, this system will be applicable to many of the pulverizing processes, especially those of food additives, pharmaceutical and cosmetic materials.

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