The Hosokawa powder tester has been used for many years to determine cohesion of bulk powders, including toner. For the first time a method is demonstrated to measure the distributions for the interparticle cohesive force, rather than just average values. The new method is demonstrated using the Hosokawa tester, by varying the amplitude of the vibration applied to a Hosokawa sieve screen, enabling the measurement of toner flow as a function of input energy. The method is demonstrated for toner particles, both without surface additives, and as a function of varying surface additive composition and loading of some typical silica and titania metal oxide additives. Toner force distributions are shown to be generally log normal. However it was also shown that poor additive dispersion, due to poor blending, can lead to asymmetric force distributions, which can deviate from a log normal distribution. Improved blending led to log normal distributions in this case as well. Both the mean and width of the distributions generally decrease with increased surface additive loading. Thus, better flow with metal oxide additives, is a result of a decrease in both peak cohesion and distribution widths.
Richard P. N. Veregin, Mandy Lam, "Measurement of Cohesive Force Distributions in Powder Flow: The Effect of Metal Oxide Surface Additives on Xerographic Toner" in Journal of Imaging Science and Technology, 2003, pp 418 - 423, https://doi.org/10.2352/J.ImagingSci.Technol.2003.47.5.art00008