Compressional Behaviour of an Agglomerated Cellulose Powder

Powder and mechanical properties of microcrystalline cellulose with different degrees of polymerization

This study investigated the influence of the degree of polymerization (DP) of cellulose materials (microcrystalline cellulose [MCC]) on some powder properties and the compression behavior of these materials. The DP was determined by measurements of viscosity (H). The weight average of molecular weight and the weight average of the different DPs were investigated after MCC was modified to cellulose tricarbanilate by light scattering measurements. The DP showed a remarkable influence on the physicochemical properties of the cellulose materials and, consequently, on the behavior of these materials during compression. MCC types with a high DP value showed greater water absorption than the types with a low DP value. No relevant relationship between the crystallinity index and the DP could be observed. DP 190 showed lower compactibility and compressibility parameters than DP 244 and 299. No significant differences could be observed between DP 244 and 299 when the same particle size fraction was compressed. Furthermore, the compressibility was increased by increasing the DP.

Influence of granulating method on physical and mechanical properties, compression behavior, and compactibility of lactose and microcrystalline cellulose granules

The physical and mechanical properties of lactose (LC) and microcrystalline cellulose (MCC) granules prepared by various granulating methods were determined, and their effects on the compression and strength of the tablets were examined. From the force-displacement curve obtained in a crushing test on a single granule, all LC granules appeared brittle, and MCC granules were somewhat plastically deformable. Inter-granular porosity epsilon inter clearly decreased with greater spherical granule shape for both materials. Decrease in intragranular porosity epsilon intra enhanced the crushing force of a single granule Fg. Agitating granulation brought about the most compactness and hardness of granules. In granule compression tests, the initial slope of Heckel plots K1 appeared closely related to ease of filling voids in a granule bed by the slippage or rolling of granules. The reciprocal of the slope in the succeeding step 1/K2 in compression of MCC granules indicated positive correlation to Fg, while in LC granules, no such obvious relation was evident. 1/K2 differed only slightly among granulating methods. Tensile strength of tablets Tt obtained by compression of various LC granules was low as a whole and was little influenced by granulating method. For MCC granules, which are plastically deformable, tablet strength greatly depended on granulation. Granules prepared by extruding or dry granulation gave strong tablets. Tablets prepared from granules made by the agitating method showed particularly low Tt. From stereomicroscopic observation, the contact area between granule particles in a tablet appeared smaller; this would explain the decrease in inter-granular bond formation.

Modification of physical characteristics of microcrystalline cellulose by codrying with beta-cyclodextrins

In an attempt to modify the physical properties of microcrystalline cellulose (MCC), the slurry form of this material was codried with beta-cyclodextrin (beta-CD). MCC slurry was blended with beta-CD at concentrations of 10%-50% w/w as a dried mass relative to MCC. The mixtures were then granulated with water and codried at 60 degrees C for 12 h or until a constant weight was reached. Codried granules were pulverized, and the fraction between 61 and 150 microns in size was reserved. The powder and tableting properties of the codried products were compared to those of various grades of MCC and the corresponding components and physical mixtures. The results showed that the products of MCC codried with beta-CD significantly improved the flowability of MCC powder. It is probable that the improved flowability was due to the more rounded shape of particles formed with this codried process, which was confirmed by SEM photographs. Moreover, the compactibility and disintegration properties of tablets produced from the codried products were even better than those using MCC alone, physical mixtures, or various grades of MCC. MCC in a slurry form was more efficient than the existing MCC products in achieving these results, which is postulated to be due to the greater amount of water required and the higher solubility of beta-CD in water promoting the interaction between beta-CD and MCC during granulation. In conclusion, MCC codried with beta-CD provides a useful excipient for direct compression.