Techniques to assess film coatings and evaluate film-coated products

Background: Polymeric film coatings have been applied to pharmaceutical solids for decorative, protective, or functional purposes. The application process is quite complex, with variables related to the coating formulation, substrate properties, processing parameters, and interactions thereof, all of which can affect product performance. Objective: This article describes a number of experimental techniques used to determine the physical, mechanical, adhesive, thermal, and permeability properties of free and applied films. These analytical tools can be used to optimize product performance, advance our knowledge of the film formation process, and investigate interactions between the coating and the solid surface. Conclusion: Through a better understanding of film-coating processes, the cause of problems that arise during manufacturing, defects observed in the coating, and changes in performance upon subsequent storage may be more quickly and accurately resolved.