Heterogeneous two-phase systems are thermodynamically unstable systems and are prepared from two liquids that do not mix with each other. In order to achieve stability, it is required to add an emulsifier or a combination of them. They form an interfacial film around the drops, thus reducing the interfacial energy and consequently increasing the stability of the system. Instability is expressed by different reversible (flotation, sedimentation and flocculation) and irreversible (Ostwald growth, phase inversion and coalescence) conditions. In producing the emulsions, the internal and external phases are combined; however, in the case of waterless emulsion concentrates, only the internal phase is used, which in our particular case consists of oils as well as selected and suitable emulsifiers. Adding only a portion of water (not the entire amount) to the internal phase results in the formation of an emulsion concentrate, and adding the whole amount of water phase creates the final emulsion. Final emulsion is always subject to instability, which is, however, not relevant in the case of waterless emulsion concentrate. Nonetheless, it is partially relevant in the case of emulsions´ concentrate. After adding the whole (final) amount of water phase to the emulsion concentrate, the resulting emulsion can only be stable for a short time, however which is still long enough to be used and consumed for a specific agrotechnical measure.
The aim of the master's thesis was to develop and prepare stable heterogeneous dispersion systems and evaluate their stability through appearance and with an optical microscope, along with measuring the pH of stable emulsions. In doing so, three types of systems were developed: waterless emulsion concentrates, aqueous emulsions concentrates and final O/W emulsions. We firstly determined a suitable emulsifier or emulsifiers´ mixture to stabilize our oil/water system. It was our aim to assure at least temporary stability of final emulsions, about 24 hours, as our final product, i. e. O/W emulsions, will be intended for immediate use. In order to get as close as possible to the conditions and end users, we only made systems by hand-stirring. Samples varied in the composition and proportions of the internal phase as well as in the content of emulsifiers.
The final results showed that a combination of two emulsifiers is required to stabilize our system. The hydrophilic Atlas␢ G-5002L and lipophilic Span® 80 were suitable. In all cases of O/W emulsions using only one hydrophilic or lipophilic emulsifier proved to be unstable immediately after the production and some also incapable for redispersion. The most stable systems were the cases in which the oil phase fraction was equal to that of the emulsifiers. The smaller the proportion of emulsifiers, the less stable the final O/W system.
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