Determination of Agglomerate Strength

For these reasons, Rumpf proposed the determination of tensile strength of agglomerates for scientific investigations. Data from such tests can be compared with each other, approximated by physical models, and described by theories. Because, with a high degree of probability, failure occurs always due to the highest tensile strain, Rumpf s proposal is justified. 

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Although many problems exist in regard to the physical significance of data obtained by compression testing, this method is an easy and fast procedure for the determination of agglomerate strength for quality control in industrial applications, for example. 

B. Park, D. Smith, S. Thoma, Determination of agglomerate strength distributions part 4. Analysis of multimodal particle size distributions. Powder Technol. 76(2), 125-133 (1993). doi 10. 1016/50032-5910(05)80019-1... 

S.G. Thoma, M. Ciftcioglu, D.M. Smith, Determination of agglomerate strength distributions. Part 2. Apphcation to model agglomerates. Powder Technol. 68(1), 63-69 (1991). doi 10.1016/ 0032-5910(91)80064-P... 

Figure 45. Methods for scientific determination of the strength of agglomerates and particle collectives, (a) Crushing strength (b) shear strength (c) and (d) tensile strength of strongly bonded agglomerates (e) and (f) tensile strength of loosely bonded particle collectives...

Figure 45(c) shows in principle the adhesive method for the determination of tensile strength. 3 Cylindrical agglomerates with two parallel, flat ends are centrically cemented between two so-called adapters. To eliminate bending stresses it is necessary to machine spherical or nonsymmetrical agglomerates into cylindrical specimens using a special method (Figure 47). This sample is fastened to thin wires and subjected to tensile forces in a conventional testing machine (Figure 48). The tensile strength of the agglomerate is defined as the tensile force P at failure divided by the cross section of the cylindrical specimen.

All methods for the determination of tensile strength described above are too complicated and time consuming to be suitable for routine industrial quality control applications. In those cases it is the task of the test procedure to determine a specific characteristic of the agglomerate easily, quickly, and reliably. The results must only be reproducible and comparable within the own organization and a relation to theoretical predictions is normally not required comparisons with results from other plants are often not necessary or, in case of competing products, not desired. 

Fig. 5.24 depicts some laboratory methods for the determination of the strength of agglomerates and cohesive powders. Often, even in a scientific environment, the transversal crushing force is measured (Fig. 5.24a). This method is quite acceptable for...

Fig. 5.24 Laboratory methods for the determination of the strength of agglomerates or cohesive powders [B.42],...

Fig. 9.9 Agglomerate strength testers top) hydraulic four-column press for the determination of compression strength bottom) from left, rotating tube for measuring degradation at transfer points, drop test arrangement, and drum abrasion tester...

This limit, which might be referred to as the ultimate tinctorial strength , reflects the maximum degree of dispersion which can be achieved in a particular vehicle system under a certain set of conditions. However, experimental results may deviate more or less from the theoretical concepts and an ideal dispersion is not normally realized not all agglomerates are broken down entirely. This, however, is of no consequence, because even the experimentally determined ultimate tinctorial strength is by no means considered a standard for industrial application technical operations are not always allowed to go to completion, and the dispersion process is often discontinued, mainly for economical reasons. 

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