Determination of the glass transition temperature (Tg) for various grades of microcrystalline cellulose (mcc) and the effect of absorbed moisture on this parameter

摘要

Microcrystalline cellulose (MCC) is widely used as a filler and binder for wet granulation as well as direct compression tableting. It is available in a number of grades having varying crystallinity. This study is an effort to evaluate the glass transition temperature (Tg) with the crystallinity of various commercial grades of MCC using Differential Scanning Calorimetry with the conditions of a crimped pinhole pan and nitrogen atmosphere (50mL/min). Six different grades of MCC were selected for this study and were heated from 25℃ to 200℃ at a heating rate of 20℃/min twice. The glass transition temperature was determined on the second run. Onset and midpoint of the Tg were determined using the ASTM/IEC, DIN 51007, Richardson and STAR~(~R) methods. Significant variation in the Tg for the various grades were observed indicating variation in crystallinity which might, in turn, influence the tableting properties such as flow and compatibility. The various methods have shown significant deviation for a particular grade. Present studies include the determination of the effect of moisture absorption on the glass transition temperature. The various grades were exposed to different relative humidity conditions over a period of seven days and are subsequently subjected to DSC analysis together with thermogravimetric determinations for the moisture-releasing pattern for the various grades.