Estimation of organic biocide leaching rate using a modified cavity jump diffusion model

Estimation of biocide lifetime in marine antifouling coatings is of great use to improve and develop technologies. An existing model simulating the diffusion of molecules in polymer networks below glass transition temperature was employed to estimate leaching. This model was modified to allow for swelling due to water uptake and to permit evaluation of copolymer binders as well as homopolymers. This enabled prediction of biocide diffusion coefficients in polymeric coatings of various binder types, including pMMA, a pMMA/butylacrylate binder containing rosin, and a trityl copolymer, using usnic acid as a ‘model’ biocide. For comparison with modelling results, coatings fomulated using each binder type were also submitted to static and dynamic seawater immersion. Fluorescence microscopy techniques were used to quantify biocide leaching from these coatings relative to unimmersed coatings. Agreement of the modified diffusion model with experimental data was good for pMMA, reasonable for the rosin-based binder, and poor for the trityl binder. Comparison of predicted and experimental biocide profiles in the binder demonstrated deviation from the expected Fickian mechanism for the pMMA binder, despite the accurate rate prediction. This work demonstrates a first approach to predicting organic biocide diffusion, and highlights the areas for future attention

Fluorescence microscopy techniques for quantitative evaluation of organic biocide distribution in antifouling paint coatings: application to model antifouling coatings

A test matrix of antifouling (AF) coatings including pMMA, an erodible binder and a novel trityl copolymer incorporating Cu2O and a furan derivative (FD) natural product, were subjected to pontoon immersion and accelerated rotor tests. Fluorescence and optical microscopy techniques were applied to these coatings for quantification of organic biocide and pigment distribution. Total leaching of the biocide from the novel copolymer binder was observed within 6 months of rotor immersion, compared to 35% from the pMMA coating. In pontoon immersions, 61% of the additive was lost from the pMMA coating, and 53% from the erodible binder. Profiles of FD content in the binders revealed an accelerated loss of additive from the surface of the CDP resulting from rosin degradation, compared to even depletion from pMMA. In all samples, release of the biocide was inhibited beyond the Cu2O front, corresponding to the leached layer in samples where Cu2O release occurred

Investigation of Chondrus crispus as a potential source of new antifouling agents

The search for environment-friendly and non-toxic antifouling (AF) paint components has led to the investigation of natural products from seaweeds. The defence metabolites used by algae to deter unwanted epibiosis have potential for harnessing and use in AF applications. Crude algal extracts may provide a suitable mixture of compounds with AF potency. Crude ethanol extracts of the macroalgae Chondrus crispus (Rhodophyceae), from both dried and fresh sources were tested and compared using bioassays based on five marine bacterial strains, five phytoplankton strains and two macroalgae to assess the AF efficacy. Dried extract from the algae had a lower minimum inhibitory concentration at 25 ?g mL?1 against the growth of bacteria and phytoplankton species than that from the fresh source. Macroalgae tests indicated that the extracts had an anti-germination activity 25–50 ?g mL?1 against both Undaria pinnatifida and Ulva intestinalis spores. A field trial of AF paint incorporating crude extract indicated an initial AF potency lasting six weeks.<br/

Designing biomimetic antifouling surfaces

Marine biofouling is the accumulation of biological material on underwater surfaces, which has plagued both commercial and naval fleets. Biomimetic approaches may well provide new insights into designing and developing alternative, non-toxic, surface-active antifouling (AF) technologies. In the marine environment, all submerged surfaces are affected by the attachment of fouling organisms, such as bacteria, diatoms, algae and invertebrates, causing increased hydrodynamic drag, resulting in increased fuel consumption, and decreased speed and operational range. There are also additional expenses of dry-docking, together with increased fuel costs and corrosion, which are all important economic factors that demand the prevention of biofouling. Past solutions to AF have generally used toxic paints or coatings that have had a detrimental effect on marine life worldwide. The prohibited use of these antifoulants has led to the search for biologically inspired AF strategies. This review will explore the natural and biomimetic AF surface strategies for marine systems