The influence of moisture content on the consolidation properties of hydroxypropylmethylcellulose K4M (HPMC 2208).

The effect of moisture content, compression speed and compression force on the compaction properties of HPMC K4M has been evaluated. As the moisture content increased from 0 to 14.9% w/w, the thickness of HPMC K4M compacts increased at constant compression force and speed. This increase in moisture content also resulted in a marked increase in the tensile strength of the tablets. At a speed of 15 mm s-1 and force of 10 kN, as the moisture content increased from 0 to 14.9% w/w, the tensile strengths increased from 1.34 to 8.54 Mpa. Equivalent tensile strengths could be obtained with less compression force as the moisture content in the polymer was increased. Increasing the compression speed generally decreased the tensile strength of HPMC K4M tablets. The dependence of tablet porosity and tensile strength on compression speeds showed that HPMC K4M is consolidated by plastic deformation. At all compression speeds, an increase in moisture content reduced the percentage elastic recovery of HPMC compacts due to greater tablet consolidation. The lowest elastic recovery (1.18%) was found for tablets made at 15 mm s-1 and 5 kN, containing 14.9% w/w moisture content.