Comparative evaluations of powder and mechanical properties of low crystallinity celluloses, microcrystalline celluloses, and powdered celluloses

Abstract

The purpose of this study was to examine and compare the powder and mechanical properties of different batches of low crystallinity powdered cellulose (LCPC-S1 to LCPC-S5) with those of commercial microcrystalline celluloses (MCC) (Avicel PH-101, Avicel PH-102, Avicel PH-103, Avicel PH-301, Avicel PH-302, and Emcocel 90m) and powdered celluloses (PC) (Solka Floc BW-40 and Solka Floc BW-100). Both the LCPC and MCC products were aggregated powders, whereas, the PC materials showed a fibrous structure. The primary particles forming the LCPC aggregates, however, were smaller in size and showed a greater degree of coalescence between boundaries, than those forming the MCC aggregates. The LCPC materials had significantly higher bulk and tap densities and lower porosity values compared with the MCC materials. The yield pressure value calculated from the linear region of the Heckel curve for LCPC varied between 48 and 70 MPa, for Avicel and PC materials between, 80 and 106 MPa, and for Emcocel 90m was 48 MPa. These results suggest that the LCPC products and Emcocel 90m, compared with commercial MCC and PC excipients, undergo plastic deformation at relatively lower compression pressures. The total volume reduction (i.e. compressibility), determined by calculating the area under the Heckel curve (AUHC), however, was comparable for all materials, with the exception of the LCPC-S3, which owing to the low yield pressure value, showed the largest reduction in volume. With the exception of LCPC-S1 and Solka Floc BW-40, all the other materials formed compacts, whose strength ranged from about 522 to 799 MPa 2. The strengths of LCPC-S1 and Solka Floc BW-40 compacts, in contrast, were 214 and 257 MPa 2, respectively. Irrespective of the solid fraction levels, the LCPC compacts, in general, disintegrated much faster than the MCC and PC compacts. In conclusion, the results suggest that the new LCPC materials reported herein have powder properties that are quite different from the MCC and PC materials evaluated, and show clear potential as direct compression excipients.