Incorporation of benzoic acid and sodium benzoate into silicone coatings and subsequent leaching of the compound from the incorporated coatings

Benzoic acid and sodium benzoate, two less toxic antifoulants as compared to currently used biocides in marine biofouling protection, were incorporated into silicone coatings to investigate their release behaviors and antifouling capabilities. It was found that benzoic acid, although exhibiting excellent antifouling capability, formed large crystals inside the coating regardless of the solvent used to increase its miscibility with silicone. The large crystals were found to be responsible for the fast leaching of the compound from the carrier coating, thus eliminating the long-term usefulness of the coating. Sodium benzoate, which was highly immiscible with silicone, was able to be incorporated into silicone in the form of small aggregates, and by tuning the preparation conditions, the aggregate size (hence the number of aggregates) could be varied. Leaching of sodium benzoate from silicone was determined to be much slower than that of benzoic acid, and a direct relationship between the leaching rate and the number of aggregates was observed. The sodium benzoate incorporated coating was found to exhibit enhanced antibacterial performance, and, for coatings containing 1 wt.% of sodium benzoate, a ∼50% reduction in bacterial attachment was achieved.