Stress transmission coefficient is a reliable and robust parameter for quantifying powder plasticity

Powder plasticity parameters derived by existing methods are sensitive to errors in porosity measurements resulting from inaccurate measurements of compact density, true density, or both. Using a number of materials exhibiting plasticity over a range of more than two orders of magnitude, the post-powder densification stress transmission coefficient (STC) strongly correlates with all four existing in-die and out-of-die plasticity parameters. Since the STC determination requires only axial and radial stress measurements, it is free from errors in the determination of tablet porosity suffered by other existing methods. Additionally, the STC is immune from user error, because data can be collected by a computer using a compaction simulator with an instrumented die. Overall, the STC is an excellent alternative to traditional powder plasticity parameters for guiding the tablet formulation design in early stages of drug development.