X-Ray diffraction and microcalorimetry study of the alpha->beta transformation of tripalmitin

The polymorphic alpha --> beta transformation of tripalmitin was studied using two independent methods-thermodiffractometry and microcalorimetry-in the temperature range from 25.0 to 42.5 degrees C. DSC was used as a preliminary tool to interpret the transformation process. In the DSC-scan the transition consisted of one endothermic and two exothermic peaks, one after the other, but in the isothermal microcalorimeter measurement the transition was a resultant of these three processes. The average reaction enthalpy was -45.6 J/g and -47.0 J/g by microcalorimetry and DSC, respectively. The concentration versus time curve of beta-state during the alpha --> beta transformation was fitted using the Avrami equation. The activation energy associated with the transformation was 410 kJ/mol as measured by thermodiffractometer and 455 kJ/mol by microcalorimeter. The uniformity of the results proved that these methods were reliable tools in the study of this thermally activated process.