EUTECTIC MIXTURES FOR PHARMACEUTICAL APPLICATIONS - A THERMODYNAMIC AND KINETIC-STUDY

The thermodynamics and kinetics of the solidification process of sever al mixtures of SR 33557 and PEG 6000 have been analyzed by differentia l scanning calorimetry. The calculated phase diagram showed a negative interaction energy between the constituents in the liquid phase. A un ified description for solidification accounting for isothermal and con tinuous cooling is resented. The onset of solidification shifts to hig her temperatures on decreasing the cooling rate and to longer times on decreasing the annealing temperature under continuous cooling and iso thermal holding, respectively. The analysis is based on the fact that nuclei have to be created prior to any crystal growth. The driving for ce for nucleation is considered proportional to the undercooling, Delt a T(= T-L - T). By coupling the isothermal and continuous cooling expe riments, the high temperature part of the time-temperature transformat ion and temperature-cooling rate transformation diagrams are construct ed under a wide range of conditions. (C) 1997 Elsevier Science B.V.