Glassy state of pharmaceuticals. IV. Studies on glassy pharmaceuticals by thermomechanical analysis

The glassy state of indomethacin was examined by thermomechanical analysis (TMA). The influences of the method of preparation and the measurement conditions of the sample on the TMA curves were investigated. The TMA curves of glassy indomethacin having hemispherical and plane surfaces were examined. Expansion was observed on the TMA curves in the region of glass transition temperature (Tg), which had been confirmed by differential scanning calorimetry. The TMA curves for the sample with the plane surface showed distinct expansion. It was further found that the glass transition shifted to lower temperatures as the heating rate was decreased and the loading increased. The TMA curves of brucine, griseofulvin and phenobarbital were similar to that of indomethacin. The relaxation process of glassy indomethacin below Tg was followed in terms of the variation of mechanical properties of samples.