Conclusion
Understanding formulation factor effects on free-film and coating-film properties would provide guidelines for selecting a
formulation in the early design stage of developing semipermeable membranes. The results from this study demonstrated that
formulation factors such as plasticizer and water level, signifantly affect free-film properties and coating performance.
With increasing plasticizer level, the mechanical strength of the free films decreased and the permeability of the films increased.
With the interaction of plasticizer and water, the effects on the properties of free films were even greater. Although there
were no significant differences in free film properties between CA-398-10NF-EP and CA-398-10TG, the permeability of coating
films increased with decreasing acetyl content in CA polymers. The acetyl content over a range of about 1.0% affected permeability
of coating films at some degree and the effects were largely dependent on the formulation. With higher plasticizer level and
water level in the formulation, the acetyl content only slightly affected the permeability of the coating film. This study
demonstrates that it is important to design a robust formulation to reduce the variability of a finished product. It should
be realized that besides formulation factors, processing conditions are key controls in ensuring product quality and keeping
the release profile of a product in a desirable range.
Jinghua Yuan* is a principal technical service representative, Doug Dunn is a senior lab technician, Nancy M. Clipse is a research analyst, and Ray J. Newton, Jr. is a senior research associate, all at Formulation Products Lab, Pharmaceutical Formulations Group, Eastman Chemical Company,
Kingsport, TN 37662, tel. 423.229.8627, fax 423.224.0414, jinghua@eastman.com
*To whom all correspondence should be addressed.
Submitted: May 6, 2008. Accepted: Oct. 1, 2008.
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