Preventing tablet defects through vacuum-assisted deaeration of a powder bed

Lamination is a common defect observed during pharmaceutical tablet compression and can be attributed to air entrapment (lamination type 1) within the powder bed. In this study, a novel vacuum-inducing chamber was implemented to remove air from the powder bed prior to compaction, thereby enabling, for the first time, a systematic investigation of lamination type 1 while decoupling air entrapment from other contributing factors. Microcrystalline cellulose (MCC) was compacted on a Huxley Bertram compaction simulator equipped with a vacuum chamber under systematically varied compressive stresses, strain rates, and ambient air pressures. Consistent with established findings, reducing compressive stress and strain rate decreased the frequency and severity of lamination defects, supporting the role of process parameters in defect formation. However, when the ambient air pressure surrounding the die and punches was sufficiently reduced, lamination defects were reduced or eliminated across the range of process parameters studied. These findings provide direct experimental evidence that modulating ambient air pressure can influence lamination defects due to air entrapment in MCC tablets. Furthermore, numerical simulations of air pressure evolution upon compression showed that altering air pressure can have a greater impact on air pressure reduction than processing conditions. The novel vacuum chamber approach offers an experimental platform for studying defect formation and suggests that control of ambient pressure during compaction may represent an effective strategy for mitigating lamination type 1 during pharmaceutical tablet manufacturing.