Influence of the unloading conditions on capping and lamination: Study on a compaction simulator

Capping and lamination are classical industrial issues that can be challenging during the scale up of solid dosage forms. Previous publications showed that changing the unloading conditions (triaxial decompression, loaded ejection) made it possible to mitigate capping. In the present study, a systematic study of the effect of the unloading conditions on capping and lamination was performed using a compaction simulator. One model formulation for capping and one for lamination were studied. When symmetrical decompression was performed, as on a rotary press, capping (on both side of the tablet) and lamination were obtained. Asymmetrical unloading (fixed lower punch during unloading) made it possible to suppress lamination and to limit capping to the upper face of the tablet. This unloading condition is similar to the unloading on an eccentric press with a stationary lower punch. Finally, loaded ejection (small pressure on both sides until the end of ejection) made it possible to eliminate both capping and lamination. By changing the unloading condition, it is possible to obtain defect free tablets even for formulations with a high capping or lamination tendency. Moreover, experiments performed on an eccentric press showed results similar to those obtained for asymmetrical unloading on a compaction simulator. Anticipation of tablets defects during the development on eccentric presses might thus be complicated especially in the case of lamination.