Non-Newtonian Characterization of Gelatinized Corn Starch Dispersions with Magnetic Particle Enhancement Under Shear Stress

Abstract

Starch-based dispersions continue to be of interest as non-Newtonian fluids because of their availability, biodegradability and sensitivity to applied shear stress. It is significant that one understands how their flow behaviour can be altered with the help of particulate additives both in characterizing materials and in feasibility studies due to their applications. The steady-shear rheological behaviour of gelatinized corn starch-water dispersions using locally sourced yellow and white varieties of corn was studied in this work, at a fixed formulation of 20 g starch in 350 mL of water. The loading levels of 0 g, 2 g and 4 g of iron filings were added and the rheological measurements were done under the influence of a static magnetic field using a rotational viscometer. The power-law model was used to analyse the data on apparent viscosity to quantify shear dependence through the flow behaviour index (n) and consistency parameter (lnµ). All fixed formulations of the starch were non-Newtonian and shear thinning, and all flow behaviour indices were found to be less than one under the conditions considered. The iron filings had a quantifiable effect on the viscosity and consistency, and this means that the resistance to flow under shear was increased. These findings offer controlled rheological insight into magnetically modified corn starch systems and also in their plausibility as shear-dependent, energy-dissipating media for further investigation in applied material systems.