Factors Affecting Polymeric Coatings

Bodmeier R, Guo X, Pacratakul O. Process and formulational factors affecting the drug release from pellets coated with the ethylcellulose-pseudolatex aquacoat. In McGinity JW, ed. Aqueous Polymeric Coatings for Pharmaceutical Dosage Forms. 2nd ed. New York Marcel Dekkcr, Inc., 1997 55-80. 

Polymeric film coats are usually quite thin with typical thickness ranging from lO to 100 pm. Thin film coats are advantageous in many respects as discussed previously however, thin film coats can be disadvantageous as even minor defects can substantially affect film continuity and functionality. There are numerous types of film coat defects that result from processing factors, formulational factors (both film and substrate), or a combination of the two. Visual inspection of coat defects is often sufficient to diagnose the underlying cause and make the necessary adjustments to reduce further defects. 

While there are abundant reasons for academic consideration of porous-matrix oxide-oxide composites, much of the practical interest, and opportunity to pursue them, is owed to two factors the economical availability of numerous types of fibers, and the absence of the necessity to coat fibers. Both of these factors significantly affect the ease and cost of experimentation, and, more importantly, the ultimate cost of the materials. An additional significant advantage is that in many cases fabrication can be very similar to that employed for polymeric composites.The majority of this section is therefore focused on porous matrix composites, since these materials are the most mature. Research on composites containing interface coatings is also addressed in this section (4.3). 

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