Sol-gel composite films with controlled release of biocides.

The release of biocides (benzoic, sorbic and boric acids) incorporated into modified silica films was investigated with respect to composite structure. The liberation rates of the embedded acids are proportional to the biocide-to-silica ratio and are changed by adding soluble polymers such as hydroxypropylcellulose. The rates of liberation correlate with biocidal activity, i.e., the growth of microorganisms such as Escherichia coli, Lactobacillus plantarum and Penicillium sp. is strongly suppressed by contact with such composite films. In a similar way, strong fungicide and insecticide effects were observed after impregnating wood with composites containing boric acid.