Current Alternatives for In-can Preservation of Aqueous Paints: A Review

With the transition towards more sustainable paints formulations based on waterborne environment, their susceptibility for microbial contamination has to be better controlled in order to increase shelf life and functional lifetime. However, recent restrictions in European regulation on use of biocides have put limitations on the possibilities for traditional systems providing either in-can or dry-film preservation. The commercial technologies for in-can preservation that are currently available are based on 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) or 2-methyl-4-isothiazolin-3-one (MIT). At present, only limited number of alternatives can be used and are reviewed in this presentation. The examples of non-sensitizing biocidal components for coatings may include quaternary/cationic nitrogen amines, silver ion or zinc complexes. However, the use of the latter is not without risk for human health. Therefore, it is believed that disruptive methods will need to be implemented in parallel with bio-inspired solutions. In particular, the antimicrobial polymers, amino-acid based systems and peptides have similar functions in nature and can offer potential for antimicrobial activities. Also cross-border solutions currently applied in food or cosmetics industries need to be considered as examples that need be adapted for paint formulations. However, the incorporation in paint formulations remains challenging in respect of the stabilization and rheology control of the system. The overview in this work aims to provide different strategies and best evidence for future trends.