Slow release of a biocidal agent from polymeric microcapsules for preventing biodeterioration

Water-soluble biocides are prone to excessive leaching and high concentrations are therefore required in surface coatings for successful protection of a surface against biodeterioration. Encapsulation prolongs the lifetime of biocides in different matrices by protecting them from leaching and by releasing them slowly. In this study, sodium benzoate as a model water-soluble biocidal agent and Congo Red dye as an capsulation indicator were incorporated into branched polyethyleneimines (PEIs) with molecular weights of 1300 and 5000 g/mol. Microscopic investigations verified that the Congo Red dye and sodium benzoate were entrapped within the capsules. The encapsulation capacity, release behaviour and efficiency of the encapsulated model biocide against two brown rot species Coniophora puteana and Serpula lacrymans were determined. The encapsulated water-soluble model biocide inhibited the growth of the decay fungi. The release of the biocide was based on slow diffusion from the capsules. The molecular weight of the encapsulated agent and the polyethyleneimine affected the release rate.

► Sodium benzoate and an organic dye were successfully trapped in polyethyleneimine (PEI) capsules.
► More sodium benzoate was released from higher molecular weight PEI than from smaller size PEI.
► Early growth, e.g. of Serpula lacrymans was suppressed with encapsulated benzoate.
► The efficacy of the system was based on slow diffusion of benzoate out of the capsules.