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Directional bonding in compacted microcrystalline cellulose
S Edge1, D F Steele, M J Tobyn
1Department of Pharmacy and Pharmacology, University of Bath, UK. prssje@bath.ac.uk
Drug Development and Industrial Pharmacy
|November 6, 2001
Summary
Silicified microcrystalline cellulose (SMCC) compacts show greater strength than microcrystalline cellulose (MCC) compacts. Mechanical testing reveals directional strength properties in both materials, with SMCC offering more reliable strength data.
Area of Science:
- Materials Science
- Pharmaceutical Engineering
- Solid-State Chemistry
Background:
- Microcrystalline cellulose (MCC) is a widely used pharmaceutical excipient.
- Silicified microcrystalline cellulose (SMCC) is a modified form of MCC with potentially enhanced properties.
- Understanding the mechanical behavior of these materials is crucial for tablet formulation and manufacturing.
Purpose of the Study:
- To compare the mechanical properties of MCC and SMCC compacts.
- To evaluate the directional strength anisotropy of MCC and SMCC.
- To assess the reliability of different mechanical testing methods.
Main Methods:
- Tensile testing, diametric compression testing, and compression testing were performed on cubic specimens.
- Mechanical strengths were measured parallel and normal to the compaction direction.
- X-ray diffraction (XRD) was used to analyze structural anisotropy.
Main Results:
- SMCC compacts demonstrated greater strength compared to MCC compacts, particularly evident in diametric compression tests.
- Both MCC and SMCC exhibited directional strength: tensile strength was higher normal to compaction, while compression strength was higher parallel to compaction.
- Diametric compression testing yielded strength values with less variability than cubic tensile testing.
- XRD analysis indicated directional structural anisotropy, with the normal direction being more crystalline.
Conclusions:
- SMCC offers superior mechanical strength and more reliable strength data compared to MCC.
- Directional strength anisotropy exists in both MCC and SMCC compacts.
- The observed directional strength may result from increased crystallinity and/or crystallographic and mechanical keying effects, warranting further investigation.