High Pressure Micronization of Tristearate
2010
Mandžuka, Zoran | Škerget, Mojca | Knez, Željko
The effect of the pre-expansion temperature, pre-expansion pressure and storage time was studied in order to investigate the crystal form, degree of crystallinity, particle size, particle size distribution and morphology of the tristearate. The experiments were performed at pressures between 115 and 215 bar and at temperatures of 54, 60 and 70 °C with the substance being already melted. Samples were characterized immediately after the experiments and later after 3 months of storage at 5 and 20 °C. Results showed an increase in the amorphous phase. During the storage, the micronized samples re-crystallized. With time, the agglomeration was more emphasized for particles produced at higher temperatures and pressures and stored at a higher temperature. The results of X-ray analysis did not show a change in crystal form of tristearate (β′ form) before and after micronization, however, for samples stored at 20 °C slow transformation from the β′ (less stable) form to the β (more stable) form occurred. In addition, the morphology of micronized samples showed an irregular and porous shape. The re-crystallization was more evident with time for samples stored at 20 °C where needle-like crystals appeared on the surface.
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