Quantifying effects of moisture content on flow properties of microcrystalline cellulose using a ring shear tester

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In this work, we have quantified effects of moisture content, over the relative humidity (RH) range of 5-92% corresponding to 1.6-10.9% of water content, on flow properties of a grade of microcrystalline cellulose (Avicel PH102) using a ring shear cell. Several key powder flow parameters, including cohesion (τc), unconfined yield strength (fc), powder bulk density (ρb), flowability (ffc), and effective angle of internal friction (ϕe), were assessed. Powder flow properties deteriorated continuously with increasing RH, as shown by the higher fc and τc as well as lower ffc, under all stress conditions. With increasing RH, ρb increased and then decreased with a maximum at 20% RH. The ϕe initially increased, from 41 to 43 degrees, and then remained approximately constant from 20% to 92% RH. The deterioration in powder flow properties is caused by surface modification by moisture, which enhances particle-particle interaction strength. The knowledge obtained in this study is useful to achieving consistent properties of this important tablet excipient and formulations containing it.

Original languageEnglish (US)
Pages (from-to)104-108
Number of pages5
JournalPowder Technology
StatePublished - Feb 1 2016

Bibliographical note

Funding Information:
Shear cell data were collected by Sarsvat Patel. I thank Dr. Dietmar Schulze for a discussion where the inconsistent use of terminology in the powder flow literature was one of the topics. This discussion led to my decision to switch the term from “flow factor” to “flowability” in this work. I thank PhRMA Foundation for a Sabbatical Fellowship in Pharmaceutics (2014-2015).

Publisher Copyright:
© 2015 Elsevier B.V..


  • Microcrystalline cellulose
  • Moisture
  • Powder flow
  • Ring shear cell


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