[nanoPost] Water borne coatings for self-cleaning

Research Centre Sweden

Due to tougher environmental legislations and trends, the R&D focus in the coatings field during the last decade has been on replacing coatings based on organic solvents with water borne systems .

Thishas been very active in this development. Both formulation, and film formation, of water-based systems have been important parts of the research activities within coatings. This field of research is still important for this centre, for example in two consortium projects dealing with the film formation of alkyd/acrylic binders and latex systems with additives.

However, there is today a new trend towards introducing new functionalities in coatings, and this is now an expanding part of the coatings research at the centre.

Mesostructured materials are used to control the release of biocides in coatings and new structured materials are used to impart an optical functionality in camouflage coatings.

One project will focus on functionalities for improved self-cleaning of exterior coatings. In this project hydrophobic and hydrophilic surfaces will be tested for reduced dirt pickup and guidelines will be developed for formulating coatings with self-cleaning properties.

One example of an ongoing project involves the effect of associative thickeners on the migration of surfactants in polymeric films. It is known that during the early stages of film formation particle ordering occurs and water channels are created between the particles. Water-soluble material accumulates in these channels and can migrate to various interfaces. It is found that associative thickeners can increase the persistence of latex particles towards polymer inter-diffusion by assembling in the water channels. As a consequence the channels are open longer, leading to more migration of surfactants to the interfaces as compared to binder systems without thickeners.

Furthermore, we are presently exploring the possibilities of setting up a consortium project around the use of cobolt-free driers in alkyd films. The aim would be to optimise the performance of alternative driers based on Manganese drier blends or vanadium drier blends to be as close as possible to the performance of cobolt drier blends. It is foreseen that cobolt might be forbidden as an additive due to its potential carcinogenic properties and effective alternative driers are needed to replace cobolt-based driers in alkyd paint formulations.

We are also investigating the possibilities to set up a project on reduced monomer penetration into boards such as MDF. Environmentally friendly UV curable liquids are becoming increasingly popular as replacements for solvent-borne industrial coatings. The UV curable liquids are 100 % paint systems while the solvent-borne counterparts contain far less paint. The only disadvantage of the UV curable system is that upon application a portion of the monomers penetrates into fiber boards before the coating is cured and these monomers do not become cured. Since the monomers are allergenic, stay in the fiber boards and remain in the liquid state they can migrate during storage. Exposure of workers to monomers during sawing thus becomes a risk. Hence a reduced penetration of the monomers into the board would be beneficial for health and environmental reasons.