Development of a Miniaturized Capillary Rheometer for High Shear Rate Rheology of Dense Suspensions

Abstract

Traditional capillary rheometers are effective for determining high rate steady shear viscosity of non-Newtonian fluids at processing relevant conditions. However, they require substantial capital investment and dozens of grams of material, presenting challenges working with limited sample quantities or hazardous materials. Additional challenges with dense suspensions include particle bridging at the transducer orifice or die and large dead zones of aggregation resulting from the sharp entry angles from piston to die. A downscaled, “disposable” capillary rheometer termed the “miniaturized capillary rheometer” is introduced to address these challenges. This device can be created in a typical lab space at low cost and requires only single grams of sample. To validate the miniaturized capillary rheometer measurements, three different dense suspensions with different particle size and geometry (60 vol% glass microbubbles, 7 vol% fumed silica, and 20 vol% calcium carbonate) are evaluated over a range of shear rates spanning 63–1000 s⁻¹ and compared to full-scale capillary rheometry. Apparent viscosity profiles generally agree between both methods, with improved agreement in true viscosity once Bagley and Weissenberg–Rabinowitsch corrections are applied. These findings substantiate this miniaturized approach for measuring viscosity of dense suspensions, enabling studies with small material quantities at a fraction of the cost.