Evaluation of Affinisol® HPMC polymers for direct compression process applications

Affinisol (R) (Hydroxypropylmethyl cellulose) polymers with low glass-transition temperature are usually processed by Melt Extrusion and show better compressibility at lower compression pressure. This study evaluates the compaction properties and powder properties of Affinisol (R) Powder by the determination of physical properties like bulk/tapped density, angle of repose and loss on drying, an out-of-die compactability, axial expansion post-compression, effect of compression force on hardness of the compact, friability and lubricant sensitivity. The results of the evaluation of powder properties showed that the tested polymers had acceptable flow properties and low moisture content and lower yield pressure. This is evident by higher hardness of compact at lower compression pressure (up to 66 MPa) compared to HPMC E15. The friability of Affinisol (R) tablets was much lower than HPMC E15 tablets. The plastic nature of the polymers caused more than 30% loss of compressibility due to lubrication. Differential Scanning Calorimetry studies confirmed low glass transition temperature of the polymers, which can be attributed to other higher degree of substitution. Overall, Affinisol (R) HPMC polymers can be proposed as a binder or controlled release matrix former for direct compression.