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Description
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.
INTRODUCTION
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. (1)
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 water-based 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.
DESIRABLE ANTIMICROBIAL PROPERTIES
Ideally, antimicrobial materials will show efficacy against a wide variety of microorganisms, be relatively environmentally safe, be colorless and odorless, and be inert with respect to ultraviolet and visible radiation. Also, it is advantageous to formulate with antimicrobial materials which are stable across a wide range of pH and which can be processed at very high temperatures. Finally, the antimicrobial should show efficacy at relatively low levels within a coating matrix.
MARKET AND MARKET TRENDS
The total global market for biocides for 2006 is expected to be approximately $400 million U.S. dollars. The highest consumption of antimicrobial by application is in the architectural market, including interior and exterior coatings which are designed to provide protection from growth of molds and mildews. The second largest market for antimicrobials is marine antifoulants, which help prevent marine life from attaching to ship hulls and the bottoms of boats. (2)
Other markets which are expected to see growth for... |
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