Triggered-Release Biocidal Nanocomposite

Biocidal additives are vital for both the preservation of coatings in the can as well as for long-term coating integrity after application. Antifungal additives are critical for delaying an attack by fungal and algal growth once an architectural coating is in place. Biocidal coatings are designed to kill microbes and fungi by slowly and steadily releasing biocide from the dried film. Unfortunately, this mechanism also is responsible for the ultimate deactivation of the biocidal activity. Once the biocide has leached out or washed out of the coating, all protection against microbes is lost. The protection of the coating by the biocide typically lasts for only about 18 months, and even less in hot, humid environments such as the South and Southeast United States. In humid climates, once the biocides have leached out, a new coating must be reapplied, often after a labor-intensive washing or removal of the previous coating. This process creates a variety of undesirable environmental impacts, from the contamination of surrounding areas by nonspecific biocide leaching to the volatile organic compounds (VOCs) emitted during the reapplication of the coating. A system that prolongs biocidal coating lifetimes and decreases the environmental impacts of the current system would benefit both the environment and property owners. TDA Research, Inc., will develop a new biocidal coating system that prolongs biocidal activity by immobilizing biocidal additives in a coating. Biocides largely are wasted as they are continuously but slowly emitted, and an imbedded biocide would eliminate the undesired contamination of the surrounding area and would stay within a coating for longer time periods. A coating that retained biocidal activity for twice as long, for example, would require repainting only half as often, leading also to a decrease in VOC emissions during painting. An imbedded biocide also would prevent the formation of biocide-resistant bacteria that can form from a traditional slow-release biocide.