Powder adhesion on tools during pharmaceutical tablet manufacturing

The occurrence of defects in pharmaceutical tablets during manufacture can have disastrous consequences that impact quality, time, cost, and patients. 'Sticking', is a prominent tablet defect that results in the removal of material from the tablet surface after each compaction and its accumulation on the punch faces during tablet production. Currently, the understanding on the various mechanisms of sticking and methods of its assessment are inadequate. In this work, a novel laser reflection sensor was developed to quantify sticking with high sensitivity, live measurements, contact-free and simple to operate. The laser sensor compensates for the drawbacks of currently available techniques. Current techniques are largely unreliable or require large quantities of active drug or require stopping the press for assessment or not accessible as they require the use of specialized and complex instruments. Moreover, a novel material-sparing methodology (Single Tablet Multi-Compaction, STMC) for the assessment of sticking was introduced here. The results presented in this work demonstrate that STMC is a viable method which requires only a few tablets to assess sticking. Together, the STMC methodology and the laser sensor aim to address a pressing need in the pharmaceutical industry; that is to enable the early warning and mitigation of sticking to avoid its disastrous occurrence during production. In this work, the laser sensor enabled the discovery of a set of conditions that affect sticking that has not been reported before in literature. The effect of pre-compression pressure, punch temperature, and punch surface contamination were studied, and all found to strongly affect sticking. The results provide new insights into the complex mechanisms by which sticking occurs.