Percolation theory and compactibility of binary powder systems.

Area of Science:

• Pharmaceutical Sciences
• Materials Science
• Powder Technology

Background:

• Understanding powder mixture compaction is crucial for tablet formulation.
• Excipient properties significantly influence tablet mechanical strength.
• Percolation theory offers a framework for analyzing composite material behavior.

Purpose of the Study:

• To investigate the impact of weight ratios between polyethyleneglycol (PEG) and alpha-lactose monohydrate on tablet compaction.
• To quantify tablet tensile strength as a function of compressional stress and relative density.
• To analyze compaction behavior using percolation theory.

Main Methods:

• Mixing defined size fractions of PEG (MW 10,000) and alpha-lactose monohydrate.
• Compressing powder mixtures into tablets using a Universal Testing Machine (Zwick 1478).
• Quantifying tablet tensile strength (σT) using a two-parameter model (σTmax, γ) dependent on compressional stress (σc) and relative density (ρr).

Main Results:

• Tablet tensile strength is governed by the percolation threshold of the less mechanically stable excipient.
• The percolation threshold is influenced by the geometrical arrangement of particles within the compressed system.
• Two distinct percolation thresholds were observed when particle size distributions differed significantly.

Conclusions:

• The mechanical stability of the weaker component dominates tablet strength once it percolates.
• Particle size distribution plays a critical role in determining percolation thresholds and overall tablet properties.
• This study provides insights into predicting and controlling tablet hardness based on excipient composition and particle characteristics.