New Technology to Prepare Antimicrobial Polyimide Coatings

In December 2003, a new technology developed by Japan's Ulvac Company was able to form a 1 to 2 μm polyimide coating with antimicrobial properties. Antimicrobial films are generally prepared by adding an antimicrobial agent to the polymer, but such coatings cannot maintain antimicrobial function for a long period of time, and it is also difficult to apply a homogeneous thin layer to the surface of a product having a complicated shape. The new technology solves these problems. New coatings can be used on substrates with complex geometries. They are formed by the vapor deposition copolymerization of 3,5-diaminobenzoic acid (DBA) and pyromellitic anhydride (PMDA). The body (DBA:PMDA molar ratio of about 1:1) was introduced into a vacuum box of the Ulvac Vapor Deposition Polymerization Equipment (designated as VEP-3000) having a coated member operating at approximately 200°C and 10-5 Torr. When the substrate is heated to about 200[deg.] C., a uniform polyimide interpolymer coating is formed at a rate of about 1 [mu]m/h and can even be formed within the pores of the ceramic material. After 24 hours, the polyimide coating showed a great reduction in activity against bacteria. Potential applications for this coating include medical equipment, ceramic or metal sintered filters, and building materials.