THE EFFECT OF MOISTURE-CONTENT ON THE ENERGIES INVOLVED IN THE COMPACTION OF IBUPROFEN

The influence of moisture content and compression speed on the ejectio n force, plastic and elastic energies of ibuprofen was measured. It wa s found that moisture can significantly reduce the force required to i nitiate ejection by the breaking of tablet/die-wall adhesions. At all compression speeds, an increase in moisture content resulted in a mark ed reduction in the ejection force of ibuprofen compacts. The plastic energy was found to increase with moisture content up to 2.5% w/w, asc ribed to an increase in particle-particle interactions. Subsequent dec rease in plastic energy at higher moisture contents was probably due t o a decrease in particle interaction due to the moisture separation of the particles of ibuprofen. The elastic energy was found to decrease with increasing moisture content up to about 2.5% w/w. This is believe d to be due to the strong bonding of particles, brought about by moist ure facilitating the formation of interparticle hydrogen bonding and s o reducing the interparticle separation. Subsequent increase of elasti c energy with increasing amount of moisture beyond 2.5% w/w was though t to be due to the formation of multilayers of water at the surfaces o f the particles. This excess moisture increased the elastic energy, by decreasing particle-particle interaction.