Polyurethane foam can provide all the requirements for bacteria, mold, yeast, and algae to grow and flourish. Some polyurethane foams use "greener" ingredients that become a fantastic food source for microbes. Other types of foam, thought to be naturally resistant to microbial growth, collect organic debris from the surrounding environment.
Both types of foam are prone to the damaging effects of microbial action over time. Likewise, both foam types benefit from the use of antimicrobial additives.
Antimicrobial additives help prevent unwanted effects of microbial growth on the foam, including mal-odors, staining, and product degradation. Their mode of action depends on the active ingredient used.
Need an introduction to microorganisms?
Antimicrobial additives help prevent the growth of bacteria, mold, and mildew in and on polyurethane foam. Inhibiting the proliferation of microbes in polyurethane foam, reduces microbial-associated odors, maintains esthetic appeal, and minimizes degradation. Ultimately, this leads to extended product life, economic savings, and less material going to landfills since treated products do not need to be replaced as often.
Studies have shown Ultra-Fresh treatments are also effective in helping to prevent dust mite colonies from becoming established in treated articles (please see regulatory information regarding dust mite claims).
What's the difference between antibacterial and antimicrobial?
Historically, the polyurethane foam industry viewed 10,10'-oxybisphenox-arsine or "OBPA" as the golden standard in antimicrobial protection. This arsenic-based biocide was preferred due to its low cost and antimicrobial effectiveness.
Today, OBPA cannot be used in Europe since it is not BPR listed and goods imported into the EU are not allowed to contain this biocide.
As a result, a newer generation of more environmentally friendly and equally effective, antimicrobial additives for polyurethane foam have been developed.
The most common additives used to manufacture antimicrobial polyurethane foam include various isothiazolinone treatments, zinc pyrithione, thiabendazole, silver, and quaternary ammonium compounds. Each active ingredient has its strengths and weaknesses.
For example; zinc, silver, and quats have strong efficacy against bacteria but their efficacy against fungi are either non-existent or high levels of the antimicrobial additive is required. Likewise, isothiazolinones and thiabendazole have robust efficacy against fungi but are less effective against bacteria or require more of the active to work effectively.
Synergistic combinations of different actives can lower overall anti-microbial use levels, provide economical savings, and most importantly, deliver superior antimicrobial performance.
By specially formulating different antimicrobials together, the Ultra-Fresh family of antimicrobial additives for PU foam is unique compared to off-the-shelf products sold by larger biocide suppliers.
Ultra-Fresh treatments offer highly effective treatments with bacterial and fungal efficacy, using lower levels of product. This lowers the manufacturer's overall costs while providing excellent antimicrobial protection.
In addition, we are proud supporters of CertiPUR-US and Europur.
Antimicrobial additives are typically added directly to the liquid polyol stream prior to the polymerization reaction. To control the physical properties of the foam, minor adjustments to the foam formulation may be required.
The antimicrobial additive becomes a permanent part of the structure once it is incorporated into the polyurethane foam. As a result, the antimicrobial treatment can last for the effective life of the product.
Many test methods developed by organizations such as the American Association of Textile Chemists and Colorists (AATCC); American Society for Testing and Materials (ASTM); International Organization for Standardization (ISO); and Japanese Industrial Standard (JIS) are available to measure antimicrobial performance.
Such standardized test methods are often developed for specific types of materials, end-uses, or antimicrobial technologies. Therefore, it is very important the right test methods are selected.
Manufacturers looking to assess the bacterial efficacy of their antimicrobial polyurethane foam should use the ISO 20743 (JIS L 1902). The ASTM E2149 Shake Flask test method is recommended to assess antimicrobial foams when silane quat based chemistries have been used.
For marine applications, where pink staining is a common problem, the ASTM E1428 test method is required. This method uses pink staining bacteria, Streptoverticillium sp., to assess susceptibility to staining. For more information about pink staining, read our blog article titled "Pink Stains on Vinyl: A Problem".
For assessment against mold and mildew, the AATCC Method 30, Part III, or the ASTM G21 are recommended.
There are a variety of third-party labs, available all over the world, to assess the bacterial and fungal efficacy of antimicrobial polyurethane foam using the test methods listed above.
Our company is unique in that we offer our customers laboratory testing services at no additional cost. During the initial development of an antimicrobial treatment program, this helps to optimize use levels while ensuring desired efficacy. Once the program is established, complementary routine testing is available as part of an ongoing quality control strategy.
If third-party verification is necessary, our complimentary testing services offer significant cost savings. Samples can be screened by our laboratory prior to submission to a third party, offering peace of mind confidence that the antimicrobial PU foam will meet all specifications.
The photos below exemplify the benefits of adding antimicrobial additives to polyurethane foam. Under the right conditions, mold and mildew can breakdown the polymer structure of the foam and use it as a food source. Antimicrobial polyurethane foam resists fungal attack.
Both foam samples were photographed after the ASTM G21 (28 days) test method.
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Untreated polyurethane foam
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Ultra-Fresh antimicrobial polyurethane foam
Below are two-time lapse videos.
The first shows an untreated rebond foam while testing using the AATCC Method 30 during the 7-day incubation period.
The second demonstrates the effectiveness of Ultra-Fresh antimicrobial treatment in the prevention of fungal growth on rebond foam.
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Untreated Rebound Foam
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Treated rebound foam
The photos below demonstrate the efficacy of antimicrobial polyurethane foam.
Two PU foam samples, one treated with Ultra-Fresh antimicrobial additive and another without an antimicrobial treatment, were tested using the ISO 20743.
The same amounts of bacteria (Klebsiella pneumoniae) were added to each sample and then incubated at 37C/98F (body temperature) for 24 hours.
Afterward, both samples were assessed to determine how many bacteria were remaining.
As seen in the below photos, heavy amounts of bacteria were recovered from the untreated foam. In contrast, very few bacteria were recovered from the antimicrobial treated foam.
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Bacteria recovered from antimicrobial PU foam
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Bacteria recovered from untreated foam
The graph below demonstrates how antimicrobial foam performs over time. The same number of bacteria were added to a regular untreated foam, along with a foam made using the same formula with the addition of an antimicrobial additive.
The samples were incubated for 24 hours at 98F/37C (body temperature). Afterward, the number of bacteria remaining was determined.
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Bacteria recovered from antimicrobial polyurethane foam* vs untreated foam
The bacteria in the untreated foam grew exponentially (from about 50,000 to over 500,000!).
However, the antimicrobial foam had 99.9% fewer bacteria as compared to the untreated sample after the same time period.
*Subject to the performance properties of the specific active ingredient manufactured into your product. Treated product efficacy claims against specific microbes are dependant on the results of laboratory testing.
A variety of consumer and industrial applications use polyurethane and polyolefin foams with antimicrobial treatment. These include mattresses, furniture, carpet underlay, kitchen and bathroom sponges, sports equipment, automotive applications, and insulation. Common end-use areas for antimicrobial polyurethane foam include:
For more information on which Ultra-Fresh products are suitable for your antimicrobial polyurethane or polyolefin foam applications, contact us!
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