Differences In Melting Behavior Research Articles

Eutectic Temperature Determination of Preformulation Systems and Evaluation by Controlled Freeze Drying

Differential scanning calorimetry was utilized in the preformulation screening of three multicomponent drug systems at subzero temperatures. The results were demonstrated to be directly comparable to those from differential thermal analysis. The effects of formulation additives on differences in melting behavior and eutectic temperature were investigated. The effect of added sodium chloride varied widely, depending on the nature of the other components. Melting point-composition diagrams were constructed, and percent melt values at a given temperature were calculated. Both eutectic temperature and percent melt values were important to the evaluation of various compositions. Finally, controlled lyophilizations were investigated in an attempt to relate percent melt and final product physical appearance.

Study of polypropylene annealed at a temperature near its melting point

Dynamic mechanical properties as determined by a torsion pendulum were used to study the effect on the crystalline structure of polypropylene of annealing at a temperature very near to its melting point. Crystallinity values as determined by both x-ray techniques and density measurements were reported for the specimens used in this study. Differential thermal analysis was used to show the differences in melting behavior of annealed and unannealed polypropylene. It was found that, although crystallinity may increase slightly, the major effect of annealing polypropylene is an increase in the size and/or perfection of the resulting crystallites. A damping peak not normally found for polypropylene was present at −50°C. in the damping curves for those specimens annealed in silicone oil without protective wrappings. This peak was found to be due to the freezing of the absorbed silicone oil, present in the specimen as small droplets.