COMPRESSION BEHAVIOR AND COMPACTABILITY OF MICROCRYSTALLINE CELLULOSE PELLETS IN RELATIONSHIP TO THEIR PORE STRUCTURE AND MECHANICAL-PROPERTIES

Two series of microcrystalline cellulose pellets were produced by extrusion-spheronization and the size fraction 710-1000 mu m was prepared by sieving. The preparation procedure gave nearly spherical pellets with similar shape and surface characteristics but markedly different porosity and mechanical properties. The pellets compressed by permanent deformation rather than by fragmentation. The degree of pellet deformation increased with an increased original pellet porosity while the mechanical strength of the pellets was not a primary factor in the compression behaviour of the pellets. The compactability of the pellets related directly to the original pellet porosity. The results indicate thus that the pellet porosity determined the degree of their deformation during compression which in turn controlled the pore structure and the tensile strength of the compact formed. A high degree of pellet deformation gave a low intergranular separation distance in the compact and promoted the formation of intergranular bonds of a high bonding force.