A new approach for the measurement of the tensile strength of powders

A new method and equipment for the determination of the vertical tensile strength of bulk solids is described. It allows for the direct determination of the tensile strength of compacted as well as of almost noncompacted powders. For the experiments lactose and corn starch were used as model substances. The cohesion of a powder determined by means of the Jenike shear cell and the tensile strength measured using the new tensile strength tester (TST) were compared. The influence of the powder porosity on the tensile strength and cohesion, respectively was also investigated. As expected the tensile strengths determined by means of the TST are lower than the cohesions obtained from shear cell measurements. However, the ratio of the cohesions of lactose and corn starch determined by using the shear cell is the same as that calculated from results obtained by means of the TST. The results obtained from the Jenike shear cell are much more sensitive to the sample porosity than those from the TST. This observation can be explained by the different measuring principles. In contrast to the TST, the Jenike shear cell method requires that the powders have to be consolidated to a certain state. The new equipment however allows for the determination of the vertical tensile strengths of noncompacted powders. (C) 1999 Elsevier Science S.A. All rights reserved.