A comparative evaluation of the mechanical properties of various celluloses

Abstract

The influence of basic properties such as physicochemical or particle properties on the mechanical properties of celluloses with different average degrees of polymerization (D̄P̄), which included powdered α-cellulose and its degradation products as well as commercial microcrystalline celluloses, was investigated. The particle shape approached that of a sphere with a reduction in D̄P̄, causing an increase in flowability and a decrease in the cohesion of cellulose powders. H(max) and γ in the Leuenberger equation, which were considered to reflect the compactibility and compressibility of powders, respectively, were higher at a lower D̄P̄, suggesting that the particle shape and/or crystallinity of materials affected the bonding properties of a substance in tablet preparation. The mechanical strength was estimated using the crushing test for a granule and the diametral compression test for a tablet. Crushing work, W, increased with a decrease in D̄P̄, which was probably due to a decrease in granule porosity. The compression behavior of granules was estimated by the static method, using the Heckel equation. The compression coefficient, K, in this equation decreased with the crushing work of a granule, thus the reciprocal of K was expected to be a measure of granule strength. The tensile strength of a tablet increased with the crushing work of a granule in the relatively high D̄P̄ region. When the D̄P̄ was low, the crushing work of granule was high and tablet strength tended to reach a maximum.