This project investigated how various minerals of different surface areas and morphologies can be used to adsorb isothiazoline biocides for controlled-release and antimicrobial purposes. The absorption of the biocides on the mineral powders was achieved by way of using a bench high shear mill (dry process), or combining them to hydrated minerals (wet process). The characterisation of the minerals was achieved by XRF (chemical composition), XRD (crystal composition), SEM (morphology), B.E.T nitrogen (surface area), and Light Scattering (particle size distribution). HPLC was used to determine the concentration of the biocide in solution, and the Flow Microcalorimeter used to measure the bond strength between the biocide molecules and the minerals. The minerals were added to an exterior paint made according to an Imerys in-house formulation. Various modifications of this initial coating formulation were made in order to compare the biocide 2-Octyl-4-isothiazolin-3-one (OIT) release profiles from impregnated and non-impregnated minerals. Montmorillonite clay was the best performing mineral in all experiments (adsorption and desorption both from the minerals and paints films, strength of bond analysis, and bioassay). All other minerals tested carried the biocide with varying degree of success. Optical and mechanical tests performed on paint films containing various minerals suggested there were no significant differences between the films. Rheology tests demonstrated that newly developed formulations were easy to apply to a surface.
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