VISCOELASTIC PROPERTIES OF SOME PHARMACEUTICAL POWDERS COMPARED USINGCREEP COMPLIANCE, EXTENDED HECKEL ANALYSIS AND TABLET STRENGTH MEASUREMENTS

The viscoelastic properties of six pharmaceutical powders, which diffe r in the extent of fragmentation, plastic flow and elastic deformation during consolidation, were studied using various techniques applicabl e at different stages before, during and after the tableting process. The measured parameters included: the apparent viscosity and elastic c ompliance obtained from creep experiments; the yield value and elastic recovery derived from extended Heckel plots at the tableting stage; a nd the apparent failure viscosity and toughness of tablets calculated from deformation and failure measurements under diametral loading at t he post-tableting stage. The usefulness of the viscoelastic properties as indicators of tabletability is considered and explained in the con text of structural changes associated with the deformation and consoli dation of particles under load.