KINETICS OF MELT CRYSTALLIZATION AND TRANSFORMATION OF TRIPALMITIN POLYMORPHS

The rates of melt crystallization and phase transformation of three polymorphs of tripalmitin were examined by optical microscopy, X-ray diffractometry and DSC with and without surfactant additives (sorbitan mono- and tristearates). The following results were obtained: (a) Crystallization rate increased in order of .alpha.,.beta.'' and .beta.; (b) transformation rate was slower than crystallization rate for each polymorph at the same temperature examined; (c) when the most stable .beta. form was recrystallized from the melt just after the melting of .alpha., its recrystallization rate was much higher than that by simple melt-cooling; (d) surfactant additives retarded both the crystallization and transformation of all the polymorphs, yet .beta.'' was influenced the most. A mechanistic interpretation based on the molecular structures both of the melt and of each polymorph is presented.