The enhanced performance of biocidal additives in paints and coatings

The addition of film biocides to coatings is necessary to prevent microbial spoilage. The biocides must be mobile so that they can migrate to the coating interface and across the cell membrane to destroy microbes. Unfortunately, concurrent losses of biocide by aqueous extraction require the addition of relatively high initial levels. This presents problems since biocides are fundamentally toxic and at such increased levels they pose a risk to the surrounding ecosystem. Legislative directives currently in place aim to reduce the amount of biocide released to the environment. This study has shown that typical coating biocides can be encapsulated within modified silica frameworks. These porous frameworks offer a means to inhibit the aqueous extraction of the biocide. In such combinations the biocides retain their anti-microbial properties, while controlled delivery facilitates a dynamic equilibrium to maintain a minimum inhibitory concentration at the coating interface, over an extended time period. There is evidence that biocide housed in such frameworks has a longer effective activity for a given initial concentration, since it is to some extent protected from the usual environmental degradation processes. (C) 2001 Elsevier Science B.V All rights reserved.