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Effect of liquid pool concentration on chemically reactive drop impact gelation process

Haldar, Krishnayan, Chakraborty, Sudipto
Journal of colloid and interface science 2018 v.528 pp. 156-165
calcium chloride, cameras, chemical reactions, energy, gelation, gels, hydrodynamics, image analysis, liquids, mathematical models, scanning electron microscopes, sodium alginate
Coupled effects of hydrodynamics and chemical reaction during gelation process have been studied in the current work. Here, a viscous sodium alginate liquid drop impacts on calcium chloride liquid pool, chemically reacts with the pool, forms a crater, and instantaneously changes its phase from liquid to soft solid called as gel. The drop impingement height and liquid pool concentration are varied to study the effect on this process. This phenomenon is captured in a time resolved high-speed camera and the dynamics of the crater is traced using image processing technique. We also use a mathematical model for crater growth which we assume to be influenced by the rate of gelation. By validating the theoretical trend with the experimental counterpart, the gelation energy has been obtained. Scaling analysis has been executed to determine significant contributory energy in the crater growth. It is also observed that the gel swelling occurs beyond a critical concentration of calcium chloride. Also, the effect of gelation on the homogeneity and strength of alginate gel are interpreted from the surface morphology examination in scanning electron microscope. Thus a new insight of gelation process has been elucidated from the context of fluid dynamics.