Formulating Coatings With Silver-based Antimicrobials A Systematic Approach

By Kurt Davidson, Brett Moyer, Kumar Ramanathan, Andrea Preuss, Barbara Pomper

Silver-based antimicrobials have increased in popularity due to their high efficacy against bacteria and low ecotoxicity. There is growing interest in using them for antimicrobial coatings. However; formulation of these products into traditional coating systems can present some unique challenges, including film discoloration, loss of gloss, poor rheology, and shelf stability.

This article presents a systematic study of the incorporation of silver-based antimicrobials into starting point formulations of different industrial and decorative coatings, with a focus on op­timizing dispersion, storage stability, and film clarity of the coating formulation. Antimicrobial efficacy against bacteria of common interest are also presented for the optimized coating for­mulations.

Antimicrobials are chemical substances which kill or inhibit growth of microorganisms such as bacteria, fungi, and algae. These microbes feed on organic material and under conditions of high humidity can be deleterious to organic films and substrates. Antimicrobial compounds can be incorpo­rated into paints and coatings with the intended effect of increasing their durability and effective service life, and are increasingly in demand where sterile environments are required such as in the medical profession.

Paint is composed of resin (binder), pigments and fillers, solvents, and additives. Additives include surfactants, dispersants, rheological modifiers, light stabilizers, and biocides. Because in both the liquid ( especially water­based systems) and cured states paint can be susceptible to attack by mi­croorganisms, there is a need for both in-can stabilizers, which protect liquid coatings from biodegradation, as well as materials which protect cured films in the industry.