Characterization of the thermal properties of microcrystalline cellulose by modulated temperature differential scanning calorimetry

The purpose of this study was to characterize the thermal properties of microcrystalline cellulose (MCC) and to investigate the influence of water on these properties. Differential scanning calorimetry (DSC), modulated temperature differential scanning calorimetry (MTDSC), thermomechanical analysis (TMA), and scanning electron microscopy (SEM) were used to characterize MCC. Three reproducible step transitions were detected in the dry material at 132, 159, and 184degreesC; for these transitions the magnitude of the heat capacity change varied by a factor of two. Exposure of MCC to water lowers the transition temperature in a manner comparable to a glass transition. The effect of water was different for samples equilibrated to different atmospheric humidities versus water added by granulation. A change in the physical properties of MCC after granulation with high amounts of water was observed. In conclusion, it appears that MCC has glass transitions, which come in reproducible triplets, and these transitions are affected by the presence of water. Also, for the materials studied, the transition temperatures are not affected by particle size and pulp source. (C) 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association.