The size distributions of microcapsules are important in determining the surface area over which the contents of the microcapsules are released. The size distribution is generally not normal around the mean, but biased toward smaller capsule sizes, forming a mode around some characteristic diameter. In order to assess the factors effective in determining this characteristic drop size, size distribution analyses were carried out photographically at each stage of the complex coacervation process. In addition, the emulsion drop size distributions were investigated as a function of stirring rate, stirring time and phase ratio. The results agreed qualitatively with the theory of isotropy but were an order of magnitude smaller. This theory is valid for Newtonian liquids. Elongational stresses could be operative with large-sized macromolecules and a mechanism was proposed based on variation of elongational stresses with velocity and rates of extension. Elongational viscosities measured for the gelatin solutions supported the proposed mechanism.
Being a versatile ceramic, which can be used in various applications, cordierite has always been subject to optimization and research. Nevertheless, the corrosion resistance of the ceramic, synthesized from natural zeolite, has not been widely investigated. In this study, cordierite with 2:2:5 compositions of MgO/Al2O3/SiO2, respectively, was obtained from the natural zeolite. Following sintering at 1250°C for 1 h, of cordierite with 10 and 20% amount of added zirconia (ZrO2), the mechanical properties exhibited proportional amelioration, accompanied by an enhanced homogeneity and reduced microcracks. The corrosion properties were investigated via the weight loss method in 2 vol. % and 5 vol. % HCl acid solutions maintained for up to 480 h at 25, 50, and 75°C. The corrosion kinetics were evaluated from corrosion curves, followed by a calculation of the activation energies of corrosion. The results revealed that ZrO2 addition enhances the resistance, with an optimum observed for the 10% zirconia doped cordierite samples, with varying activation energies between 113 kJ/mol for 5 vol. % HCl acid solution and 119 kJ/mol for 2 vol. % HCl acid solution.
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