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ISBN 9783843936347

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Serghei Abramov
Crystallization in emulsions: Influence of formulation and process parameters on solidification in droplets

141 Seiten, Dissertation Karlsruher Institut für Technologie (2018), Softcover, A5

Zusammenfassung / Abstract

Product design of crystalline dispersions for chemical, life science and pharmaceutical applications is a challenging process engineering venture. Distinctive viscoelastic behaviour of the dispersed phase requires intensive and time-consuming processing in conventional comminution operations. Especially, the adjustment and control of size and shape is limited and narrows down the area of applications of these formulations. An engineering solution to avoid the extensive milling of viscoelastic materials and to control the size and shape of produced particles is enabled by the two-step melt emulsification process. In the first step, the dispersed phase is emulsified above its melting temperature and transferred under supercooling into a fine crystalline dispersion in the second step. Melting the dispersed phase reduces the elastic properties facilitating the emulsification of the bulk to precise droplet size. Cooling the emulsion initiates crystallization preserving the adjusted particles size and spherical shape in the crystalline structure.

Emulsification of the molten bulk to countless small volume units leads to individual and polydisperse nucleation in each droplet during supercooling. This individual crystallization behaviour depends on a variety of formulation and process parameters, such as e. g. droplet size, supercooling, dispersed phase and external forces. Ideally, these parameters are adjusted to transform all droplets into spherical crystalline particles of the same size. Eventually, incomplete crystallization often occurs in technical applications leading to colloidal processes and changes in size, shape and stability of dispersions.

Application properties of crystalline formulations strongly depend on physical state of droplets/particles within the formulation and therefore on the crystallization progress in crystalline emulsions. Thus, this research work focused on the incomplete crystallization issue and addressed three major research aspects: (1) Development of an analytical method to quantify crystallization progress in dispersed systems, (2) investigation on the impact of mechanical stress on the acceleration of crystallization in emulsions, and (3) application of the mechanical stress approach on the technical scale melt emulsification process.