APPARENT COMPRESSIVE ELASTIC-MODULUS AND STRENGTH ISOTROPY OF COMPACTS FORMED FROM BINARY POWDER MIXES

An apparent compressive Young's modulus of elasticity of cylindrical t ablets, produced from binary powder mixtures compressed at two tableti ng rates, was compared with the tensile strength isotropy expressed as the ratio of axial to radial tensile strength. The binary powder mixt ures comprised materials which differ in yield pressure and in the ext ent of elastic deformation, plastic flow and fragmentation during thei r consolidation. A log-linear correlation was found between the appare nt Young's modulus of elasticity of the tablets and the tensile streng th isotropy, indicating that they were similarly related to the compos ition of the tablets. However, some differences in the effect of compr ession rate were evident. Thus, apparent Young's modulus varied with c ompression rate, depending on the principal consolidation mechanism of the component materials. In contrast, the tensile strength isotropy w as virtually unaffected by an increase in the compression rate except for mixtures of paracetamol with Avicel which showed a slight decrease in isotropy. The tensile strength isotropy - a measure of the interpa rticle bonding isotropy - of the tablets could be improved by increasi ng the apparent Young's modulus, through the incorporation of a compon ent, the particles of which undergo fragmentation or possess a high yi eld pressure.