The use of an Elastic Recovery Index as a Criterion of Compactional Behaviour of Some Direct Compression Bases

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Abstract
The effects of compression force and holding time on computer logged strain movements (at constant stress) and elasticviscoelastic expansions (on load release) of compacts made from eight pharmaceutical powders are reported. The feasibility of using an elastic recovery index (the ratio of elastic recovery to viscoelastic strain movements) to predict the quality of a material is also discussed. All compacts continued to consolidate by viscoelastic and plastic flow when held under constant stress during the holding period. The “compressible” bases Avicel PH-101 and Sta-Rx 1500 exhibited more time dependent movements than powders such as Paracetamol DC, Paracetamol, Emcompress and magnesium stearate. Poorly compressible materials such as magnesium carbonate and paracetamol showed the greatest elastic expansions on load release. It has been found that the elastic recovery indices of the compressible materials were lower than those of poorly compressible powders.