Padma Prabodh Varanasi

Role of Hydraulic and Capillary Radii in Improving the Effectiveness of Capillary Model in Wicking

In this paper the liquid absorption under capillary pressure, or wicking, in cylindrical polymer wicks made of sintered polymer beads is studied experimentally and theoretically. Three different polymer wicks (made from Polycarbonate, Polyethylene and Polypropylene) and three different well-characterized liquids (Hexadecane, Decane and Dodecane) are used in the present experimental study. These experimental results are then compared with the predictions of the capillary model. The capillary and hydraulic radii used in the model are found to behave like two independent wicking parameters and are needed to be measured separately to improve the accuracy of the capillary model in predicting wicking in polymer wicks. Accurate measurement of the capillary radius ensured a good prediction by the capillary model of the final steady-state height in the large-pore wicks.Copyright

Viscoelastic properties of concentrated oil-in-water emulsions stabilized by mixed non-ionic surfactants

Abstract Comprehensive rheological data on well-characterized emulsions are scarce in the literature. For the present study we prepared and characterized emulsions of mineral oil in aqueous glycerol stabilized by mixed non-ionic surfactants. The viscoelastic properties of the emulsions were obtained at oil phase volume fractions ranging from 0.05 to 0.75. Steady-shear flow and oscillatory flow measurements responded well to dimensional analysis based on a hard-sphere model. This treatment permitted us to correlate the present work with results of Vadas et al. on emulsions and Kriegers findings on latex dispersions. Stress relaxation measurements were used to estimate interfacial dynamic area elasticities.