Studies on the interaction of water with ethylcellulose: Effect of polymer particle size |
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Authors: | Anjali M Agrawal Rahul V Manek William M Kolling Steven H Neau |
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Institution: | (1) Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, 5005 Rockhill Road, 64110-2499 Kansas City, MO;(2) Department of Basic Pharmaceutical Sciences, University of Louisiana at Monroe, 71209 Monroe, LA |
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Abstract: | The purpose of this research was to investigate the interaction of water with ethylcellulose samples and assess the effect
of particle size on the interaction. The distribution of water within coarse particle ethylcellulose (CPEC; average particle
size 310 μm) and fine particle ethylcellulose (FPEC; average particle size 9.7 μm) of 7 cps viscosity grade was assessed by
differential scanning calorimetry (DSC) and dynamic vapor sorption analysis. The amounts of nonfreezing and freezing water
in hydrated samples were determined from melting endotherms obtained by DSC. An increase in water content resulted in an increase
in the enthalpy of fusion of water for the two particle size fractions of EC. The amount of nonfreezable water was not affected
by the change in particle size at low water contents. Exposure of ethylcellulose to water for 30 minutes is sufficient to
achieve equilibration within the hydrated polymer at 47% wt/wt water content. The moisture sorption profiles were analyzed
according to the Guggenheim-Anderson-de Boer (GAB) and Young and Nelson equations, which can help to distinguish moisture
distribution in different physical forms. The amount of externally adsorbed moisture was greater in the case of FPEC. Internally
absorbed moisture was evident only with the CPEC. In light of these results, and explanation is offered for the success of
FPEC in wet-granulation methods where CPEC was not successful. |
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Keywords: | ethylcellulose fine particle ethylcellulose differential scanning calorimetry dynamic vapor sorption GAB equations Young and Nelson equations |
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