Evaluation of powder and tableting properties of chitosan.

The aim of this study was to analyze the process of tablet formation and the properties of the resulting tablets for 3 N-deacetylated chitosans, with a degree of deacetylation of 80%, 85%, or 90%. Material properties, such as water content, particle size and morphology, glass transition temperature, and molecular weight were studied. The process of tablet formation was analyzed by 3-D modeling, Heckel analysis, the pressure time function, and energy calculations in combination with elastic recovery dependent on maximum relative density and time. The crushing force and the morphology of the final tablets were analyzed. Chitosans sorb twice as much water as microcrystalline cellulose (MCC), the particle size is comparable to Avicel PH 200, a special type of MCC, the particles look like shells, and the edges are bent. Molecular weight ranges from 80,000 to 210,000 kDa, the glass transition temperature (Tg) was not dependent on molecular weight. The chitosans deform ductilely as MCC; however, plastic deformation with regard to time and also pressure plasticity are higher than for MCC, especially for Chit 85, which has the lowest crystallinity and molecular weight. At high densification, fast elastic decompression is higher. 3-D modeling allowed the most precise analysis. Elastic recovery after tableting is higher than for MCC tablets and continues for some time after tableting. The crushing force of the resulting tablets is high owing to a reversible exceeding of Tg in the amorphous parts of the material. However, the crushing force is lower compared with MCC, since the crystallinity and the Tg of the chitosans are higher than for MCC. In summation, chitosans show plastic deformation during compression combined with high elasticity after tableting. Highly mechanically stable tablets result.