Modeling the Air Pressure Increase Within a Powder Bed During Compression-A Step Toward Understanding Tablet Defects

Area of Science:

• Pharmaceutical Sciences
• Materials Science
• Mechanical Engineering

Background:

• Tablet defects such as cracking, bubbling, and capping are common issues in pharmaceutical manufacturing.
• Existing research suggests internal air pressure during powder compression contributes to tablet cracking.

Purpose of the Study:

• To investigate the relationship between compression parameters and internal air pressure during tablet formation.
• To couple air pressure and plasticity models to understand tablet defect formation.
• To provide a foundation for optimizing tableting processes to minimize defects.

Main Methods:

• Numerical simulation of air pressure increase in a 2D axisymmetric tablet geometry.
• Coupling of an air pressure model with a plasticity model for tablet relative density.
• Experimental validation using X-ray microcomputed tomography (micro-CT) scans at various dwell times.

Main Results:

• Increasing compression speed significantly raises internal air pressure (1-1.5 MPa), nearing the tablet's tensile strength.
• Dwell times typical of tablet presses do not reduce cracking.
• Extended dwell times (10-100s) diminish air pressure and eliminate cracking, consistent with model predictions.

Conclusions:

• The study successfully couples air pressure and plasticity models for the first time to analyze tablet compression.
• Compression speed is a critical factor in generating internal air pressure and causing tablet defects.
• Extended dwell times are crucial for mitigating air pressure-induced cracking, offering insights for process optimization.