The effect of humidity on samples of microcrystalline cellulose taken from the extrusion/marumerization process.
The purpose of this work was to examine the sorption and desorption of water by various samples of microcrystalline cellulose, MCC (Avicel PH-101), taken from the extrusion/marumerization process, and to provide data that may explain how water affects the MCC polymer matrix during the formation of beads. Two isopiestic (humidity) studies were conducted: the first used samples exposed directly to controlled humidity conditions, whereas the second used samples that were freeze-dried before being exposed to controlled humidity conditions. Water sorption and desorption were determined gravimetrically. When both sets of samples were initially exposed to low-humidity conditions, they reached equilibrium by desorbing water. When these samples were initially exposed to high-humidity conditions, the high moisture content samples desorbed water, whereas the low moisture content and the freeze-dried samples sorbed water to reach equilibrium. When the first set of samples was initially exposed to high- and then to low-humidity conditions, they reached the same water content achieved by being equilibrated directly at the low-humidity condition. However, samples that were initially exposed to low- and then to high-humidity conditions had equilibrium water contents that were lower than those achieved by being equilibrated directly at the high-humidity condition. The original MCC systems exhibit a hysteretic effect above 85%, whereas the freeze-dried systems have a broader range hysteretic effect starting at 20% relative humidity. The results suggest that the internal structure of the MCC polymer fibers must change with the sorption and desorption of water, supporting the autohesion theory.
Mayville
F C
FC
Department of Chemistry and Biochemistry, University of the Sciences in Philadelphia, Pennsylvania 19104-4495, USA.
Atassi
F
F
Wigent
R J
RJ
Schwartz
J B
JB
D000327:Adsorption; D002482:Cellulose / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical; D004339:Drug Compounding; D005079:Excipients / Q000737:chemistry*; D005612:Freeze Drying; D006813:Humidity
D005079:Excipients; D002482:Cellulose; C109691:microcrystalline cellulose