Air entrapment during tablet compression – Diagnosis, impact on tableting performance, and mitigation strategies

Air entrapment during powder compression, a phenomenon that can cause tablet defects upon decompression and ejection, was diagnosed for celecoxib powder by comparing its in-die elastic recovery profiles with and without precompression prior to the main compression. Without precompression, the elastic recovery of celecoxib compacts significantly increased from ∼4% at a main compaction pressure of 150 MPa to ∼14% at and above 200 MPa. The large increase in elastic recovery is eliminated when a precompression step is employed. The deaeration of powder by precompression resulted in higher tablet strength, accompanied by lower tablet porosity. Thus, precompression is an effective strategy to mitigate the deleterious effects of air entrapment in tablet manufacturing. We also found that, although entrapped air caused significantly higher elastic recovery, it does not affect the plasticity parameter derived from an in-die Heckel analysis.