High-Resolution Surface Texture of Elastomeric Drug Closures for Parenteral ApplicationsPolymer coatings are applied to elastomeric (rubber) closures for drug packaging when performance issues such as lubricity, barrier properties, extractables
and leachables must be controlled. Coatings can have complex compositions which lead to complex surfaces, additional surface treatments such as plasma spray or electron beam may add another aspect of complexity. Surface roughness and texture at the nanometer scale is readily examined with the atomic force microscope, which can be used as a diagnostic tool when coatings fail or unexpected results are obtained. Two examples of surface phase imaging with the AFM are shown here; a PTFE coating (above) and a parylene coating (below), both imaged at the same magnification and under identical conditions. Although surface roughness measurements
with nanometer resolution can provide useful insight, the phase image can provide a level of detail for the coating structure not available by other means. Contrast in the phase image is based on differences in mechanical properties for the materials at the coating surface, and the distribution of hard and soft elements is clearly resolved in these images. Such differences in surface texture will have a direct impact on critical properties such as lubricity. Using
AFM to assess the properties of your coatings can be a key tool for a better understanding of process and composition variables. Call
PolyInsight for more information on how your specific problem can be addressed.
