AbstractA simple method is described to obtain rheological data on filled polymeric materials in the form of powders. The powder is compacted in a cylindrical chamber by a plunger driven by the cross‐head in an Instron testing machine and the load‐displacement curve is recorded. Further information is obtained by compressing the powder to a fixed load and measuring the load decay with time (stress‐relaxation). The tests are illustrated by application to “monocomponent toner” powders used in dry copying or nonimpact printing processes. It is shown that compaction and stress‐relaxation data are able to differentiate between different toners and facilitate the prediction of their relative performances in terms of pressure fusing. A mechanical spring‐dashpot‐slider model is effective in describing the rheological behavior of these powders and its dependence on the loading of a hard filler (magnetic pigment). The latter affects the “slider” yield stress in the model but has no influence on t
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