Modification of a Cone-Plate Viscometer for Direct Recording of Flow Curves

Using a concentric-cylinder rotational viscometer, Weltmann has shown that automatic recording of flow curves in accordance with a predetermined program is important in the study of materials whose flow properties are shear-dependent and time-dependent. When the flow of such materials as greases was studied using the Ferranti-Shirley cone-plate viscometer, advantages of small sample size, ease of loading with minimum deformation, and uniform shear rate across the sample were apparent. However, time-dependent properties of the grease could not be adequately described from data obtained in manual operation of the cone-plate viscometer. An automatic control device for shear rate acceleration of the cone-plate viscometer has been designed so that flow curves can be obtained automatically using an X-Y recorder. Flow curves of typical greases and other materials exhibiting non-Newtonian and time-dependent properties have been successfully obtained using this automatic control device. The cone-plate viscometer as modified has distinct advantages for the study of non-Newtonian and time-dependent materials.