Effect of compression force, compression speed, and particle size on the compression properties of paracetamol.

The compression characteristics of two particle size fractions (< 90 microm, 105-210 microm) of paracetamol were examined. Each fraction produced extremely weak tablets and displayed a high tendency to cap. Low correlation coefficients of the initial parts of the Heckel plots, a low strain rate sensitivity, and an increase in mean yield pressure (from 34.2 to 45.5 MPa) with decrease in particle size all confirmed that the main mechanism during the compaction of paracetamol was fragmentation. The 105-210-microm particles underwent more fragmentation than the less than 90-microm powder. Heckel analysis confirmed that the larger size fraction of paracetamol produced denser compacts than the smaller fraction. The 105-210-microm fraction resulted in tablets with lower elastic recoveries and elastic energies. The elastic, plastic energy ratios indicated that the majority of energy involved during the compaction of paracetamol was utilized as elastic energy, indicative of massive elastic deformation of paracetamol particles under pressure.