![]() ![]() The aim of this study was to compare the results of applying short-chain (hexylamine) and long-chain surfactants (cetyltrimethylammonium bromide) as co-stabilizers with solid particles and to clarify the role of hexylamine in stabilizing the complex.ĭifferent types of silica were used as solid stabilizer: 1) fumed silica powder - Aerosil A-200 and A-380 with specific surface area of 200 and 380 m2/g respectively 2) Ludox HS-40 - 40 % suspension in water with surface area of 220 m2/g 3) hydrolytic silica S-3 with the particle radius 230 nm obtained via the hydrolysis of silicon esters in an alcoholic medium by the Stober method. At higher silica concentrations, the emulsions did not separate, even when sitting for several months. Using hexylamine-silica complex, we obtained extremely stable emulsions of both types: direct (oil-in-water, O/W) and reverse (water-in-oil, W/O). In the case of emulsions, the growing concentration of hexylamine even leads to a phase inversion which correlates with the contact angle inversion. Hexylamine adsorption at the silica particle's surface leads to an increase in the contact angle of wetting by water and the angle of selective wetting at the oil/water interface and hence, to an increase in the stability of emulsions and foams. The modified solid particles are attached more strongly at the interface, forming a compact protective interlayer.Ī short-chain surfactant hexylamine was used together with silica to stabilize emulsions and foams. As a result, the surface charge decreases and the contact angle 9 increases. As a result, the silica particle's surface is modified by organic molecules orienting with their hydrophobic hydrocarbon radicals out toward the water. For example, cationic surfactants are easily adsorbed at the surface of silica, which is negatively charged in the presence of water. It is usually assumed that the role of surfactant is to reduce the hydrophobicity the particle's surface. Solid particles are considered to be the main stabilizers in an surfactant-solids emulsifying complex, while the surfactant is considered to be a co-stabilizer or modifier. Such emulsions are used as a template for creating nano-microporous materials. Micrometer-sized hollow clusters (colloidosomes) are obtained from the solid-stabilized drops. Solid-stabilized emulsions and foams differ from classical surfactant-stabilized systems in that they have some specific properties: (1) extremely high stability (2) specific rheological properties connected with the structure formation at the interface and in the liquid continuous phase. Solid particles have been recently widely applied alone or together with surfactants for the stabilization of emulsions and foams. Keywords: solid particles, solid-stabilized emulsions, oil-in-water emulsions, hybrid particle. It is assumed that at high concentrations this short-chain surfactant, together with silica, forms hybrid organic-inorganic particles that are attached at the oil/water interface and promotes the formation of oil droplets in the water. So, in the case of water-in-oil emulsions, hexylamine is a completely equivalent co-stabilizer together with silica, rather than just a solid surface modifier. It is shown that water-in-oil emulsions were obtained only if the hexylamine volume fraction was greater than that of the silica (Aerosil) volume fraction in the aqueous phase. The properties of emulsions stabilized by complexes of silica particles with hexylamine are analyzed. Stabilization of water-in-oil emulsions with complex of silica particles and hexylamine ![]()
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