PC Summitry: Anit-Microbial Coatings

Posted on Sunday, September 1, 2013

By Kevin Miller

The fight against disease has been in the forefront for medical professionals, manufacturers and the general public for many years. With every flu epidemic outbreak we clamor for methods to ensure health and thwart intrepid germs from attacking the general population. With the advent of hand sanitizers and anti-microbial technology we fight bacterial and viral pathogens in the quest to disinfect our world. But do we really know what we’re fighting and are these measures truly making a safer environment? In recent years anti-microbial powder coating technology emerged as one of the tactics to battle germs. Let’s break down the elements of this technology, understand how it works and where it can help us.

What Is Anti-Microbial Technology?

The Environmental Protection Agency defines anti-microbial agents as pesticides and states: “…they are intended to disinfect, sanitize, reduce or mitigate the growth or development of microbiological organisms; or protect inanimate objects, industrial processes or systems, surfaces, water or other chemical substances from contamination, fouling or deterioration from bacteria, virus, fungi, protozoa, slime or algae.”

Some anti-microbial agents are considered sanitizers that are topically applied. Hand sanitizers and cleaning products fall under this category. These are non-residue producing materials and have no application in the coatings world because their function is temporary.

In powder coatings anti-microbial technology provides germ killing through the incorporation of an anti-microbial agent. By their nature these agents are long-lasting and persist throughout the life of the coating.

Why Consider Anti-Microbial Technology?

The most obvious reason to use an anti-microbial coating is to kill pathogens on the surfaces of products that are deleterious to human health. These include bacteria, viruses and fungi. Combating the transmission of disease can take many forms. Foremost are personal hygiene and sanitation measures such as washing hands thoroughly, properly refrigerating food products, keeping food handling utensils and appliances clean and the regular disinfectant cleaning of surfaces in the environment.

Another function of anti-microbial technology is the protection of inanimate objects. The proliferation of microorganisms can have a deleterious effect on products. Protection of a shower curtain can be used to illustrate this scenario. Anti-microbial agents can be incorporated into shower curtain materials which can keep microorganisms from damaging the curtain and thereby extending the life of the shower curtain.

Other less obvious but perhaps more business related incentives to pursue anti-microbial strategies relate to consumer awareness and competitive pressures. Indeed the proliferation of disinfectant schemes has been quite prominent in the media.

How Are Microorganisms Transmitted?

The most common means of spreading germs are from respirable transmission (coughing and sneezing) and manual contact. Microbes are delivered to the environment and under conducive conditions can exponentially reproduce into large colonies within hours.

Where Is Anti-Microbial Technology Important?

A plethora of applications can benefit from anti-microbial technology. The most obvious environments and applications include hospitals, schools, locker rooms, public transportation, food preparation, gymnasiums, spas and the handles/hardware of consumer goods.

How Are Anti-Microbial Agents Regulated?

Anti-microbial agents are considered pesticides by the US federal government and are therefore regulated by the Environmental Protection Agency. They are specifically governed by the Federal Insecticide Fungicide and Rodenticide Act (FIFRA). The laws and regulations can be found in the Code of Federal Regulations 40 CFR sections 152, 156 and 158.

The EPA recognizes two very important classes of anti-microbial substances. One deals with agents that are proven to kill microbes and therefore provide a quantifiable impact on the health of the general public. Registration requires a high level of testing by the EPA before being approved. This testing can run into the hundreds of thousands of dollars and can take years.

The second category involves EPA recognition that the anti-microbial agent can be used to protect the treated article and does not necessarily improve public health. The EPA grants the “treated articles exemption” for a non-public-health use of a pesticide that is intended to protect only the treated article or substance itself. Consumers may distinguish such products by the absence of the EPA’s pesticide registration number (found on the product label) of the registered pesticide used for protecting the article itself.

The EPA goes on further regarding how claims can be made for products that protect articles: “Claims for treated articles or substances are limited to statements like, “This product contains a preservative (e.g., fungicide or insecticide) built in or applied as a coating only to protect the product. An example of an acceptable label statement would be:

“Antimicrobial properties are built in to inhibit the growth of bacteria that may affect this product. The antimicrobial properties do not protect users or others against bacteria, viruses, germs, or other disease organisms. Always clean and wash this product thoroughly before and after each use.”

Treated kitchen accessories or other food contact articles such as a cutting board, high chair, or conveyor belt that may come in contact with food should carry an appropriately qualifying statement, such as:

“This product does not protect users or others against food-borne bacteria. Always clean and wash this product thoroughly before and after each use.”

Treated products such as bed pans and potty seats that involve potential human contact with bodily fluids or excrement (e.g., blood, vomit, saliva, urine, or feces) should carry an appropriate qualifying statement, such as:

“This product does not protect users against bacteria, viruses or other disease organisms. Always clean and wash this product thoroughly before and after each use.”

In addition, it should be noted that: “The treated articles exemption is available only for the protection of the product and not for public health uses.”

The preservative claim and qualifying statement on the product packaging (type, size color) must be given no greater prominence than other described product features.

It is very important to note that even though these statements are required by law when describing a product, the use of the terminology “Anti-Microbial” is still allowed. In using the term “Anti-Microbial,” the consumer of this technology, even though it only applies to the article and not the health of the general public, may construe the properties beyond these statements.

How Are Surfaces Tested for Anti-Microbial Performance?

Most anti-microbial testing follows the JIS-Z2801 procedure developed in Japan. Basically the surface is contaminated with a microorganism suspended in a nutrient broth to support reproduction. The contaminated sample is then left to incubate in a humid environment for 24 hours. Tests are run in triplicate, including an uncontaminated control specimen. Some evaluations are run for less than 24 hours to more closely determine kill point. At the conclusion of the test microorganisms are counted and compared to the original quantity.

A number of common microorganisms are routinely tested. These include:

• Gram-negative bacteria, e.g. Pseudomonas aeruginosa

• Gram-positive bacteria, e.g., Staphylococcus aureus, E. Coli, Salmonella

• Fungus, e.g., Aspergillus niger, Penicillium, Trichophyton mentagrophytes

• Mycobacterium (cause diseases such as tuberculosis) , e.g., M. Smegmatis, M. Fortuitum

• Viruses, e.g., MS2 coliphage an RNA virus, Polio virus

Antimicrobial results are expressed as reductions in microbial populations, and are presented in terms of Log10 reductions as illustrated in the table below.

Common Anti-Microbial Approaches

Microbes can be eradicated through a number of methods including the following residue producing anti-microbial agents:

Some of these have limited use in powder coatings because they introduce a high level of color or degrade at powder coating processing temperatures. Most common is the use of silver and more specifically silver coated zeolites that release silver ions in humid conditions.

New Developments in Anti-Microbial Technology

Recently, scientists have uncovered novel technology that provides excellent anti-microbial efficacy. This technology is just emerging however the preliminary results are quite encouraging. The powder coating materials utilize a novel anti-microbial agent developed by Agienic Microbials, Inc. Their anti-microbial technology is based on copper salts and is produced by a simple, environmentally friendly synthetic process. It does not use precious metals and can be delivered in a variety of forms.

Typically the efficacy of the antimicrobial agents is first established in dilute solutions so that it is easy to compare different materials against a variety of microbes. Agienic’s materials are effective against a broad array of microbes. Their efficacy was first established in solutions with copper concentration is 60 parts per million (ppm). This data against select microbes is provided below. Short term testing (5 minutes) was only conducted for Pseudomonas aeruginosa and Staphylococcus aureus.

This technology offers a significant advancement in anti-microbial performance. As an example when nano-silver solution was tested against Pseudomonas aeruginosa at a 60ppm metal concentration it showed a log kill of 1.6 at a time point of 24 hours. Agienic has a number of patents pending and is working on obtaining EPA registration of their products. Experimental products were made to test the efficacy of these materials in epoxy-polyester powder coatings. The coatings showed excellent processability and no degradation in mechanical properties. The antimicrobial test results on these coatings are shown above, and as shown the coatings were tested at 24hours (standard) and also at shorter times (6 hrs) to see if these were still highly antimicrobial at shorter times.


Many schemes have been developed to thwart the spread of germs and thereby improve the health of the general public and protect treated manufactured goods. In all cases good hygiene and housekeeping practices are strongly encouraged. The EPA regulates these anti-microbial agents for both the health of the public and also to protect treated articles. Recent scientific advances have identified novel technology that provides significant improvement over prevailing technology. Further testing by the EPA is expected to validate the performance of these products and make them available to the powder coating industry.

Kevin Biller is technical editor of Powder Coated Tough magazine. He can be reached at 614-354-1198 or via email at kevinbiller@yahoo.com.