A number of companies are seeking a means to make plastics, the predominant material in hospital settings, particularly within disposables, equipment, and devices, inherently resistant to the bacteria that can lead to hospital-acquired infections (HAIs). In addition to causing illness, microbes can lead to product deterioration, discoloration, malodor, and food contamination. Beyond hospitals, antimicrobials have found a wide range of applications within plastics, according to research by Niall D’Arcy of the Biocide Information Service at the University College Dublin.

Everyday items like pay phones, flooring, and escalator rails have added antimicrobials to control the growth of microorganisms, and D’Arcy notes that antimicrobials in plastics constitute a growing segment within the specialty biocides industry.

In the United States, antimicrobials are regulated by the Environmental Protection Agency (EPA) under the Federal Insecticide, Fungicide & Rodenticide Act (FIFRA), with the regulatory agency dictating that any antimicrobial claim must be directed to the material that is being protected. In function, this means companies can claim that their product has been treated for protection from degradation due to fungal or bacterial attack. What OEMs cannot claim is that the treated product will protect something or someone that may be in the immediate vicinity of your treated product. In addition, no health claims can be made for the treated product.

D’Arcy notes that in the mid-‘90s, a number of companies added antimicrobial additives to plastic kitchenware and cutting boards, subsequently making claims, for instance, that the antimicrobial-treated cutting board would kill bacteria on its surface and protect foods from cross contamination. These claims ultimately led to “hefty” fines on the OEMs that had misrepresented their products, according to D’Arcy. In the United States, before a material can be sold as an antimicrobial, it must be registered with the EPA, with the registration number posted on its label.

Taking a bite out of Crocs
Crocs, whose proprietary elastomer-based footwear found a home on feet across the United States, derived their popularity from comfort and antimicrobial claims. The company recently learned how serious the EPA is about such health-related inferences. On Jan. 3, the Colorado-based company announced a settlement with the EPA regarding unproven antimicrobial claims, paying $230,000 to settle cases involving several types of its shoes.

In addition to statements on its packaging, Crocs also made unsubstantiated health claims in advertisements and on its website. In a press report on the settlement, Sandra Stavnes, director of the EPA’s technical enforcement program in Denver, said her agency is “seeing more and more consumer products making a wide variety of antimicrobial claims,” adding that “the EPA takes these unsubstantiated public health claims seriously.”

Suppliers take note
In spite of regulatory backlash, many companies appreciate the market potential for antimicrobial plastics and are pushing forward with new products. Microban International has developed antimicrobial solutions for acetal (POM)—a material commonly used in catheter tubing and connector components that can be a source of HAIs. The company says that while acetals can be prone to chemical degradation and formaldehyde off-gassing in the final product when additives are introduced to it, its new antimicrobial is compatible with acetal and causes no destabilization or formaldehyde generation.

In-house testing reportedly showed more than four log reductions against a variety of organisms using Microban’s standard, enhanced, and human-serum-based testing protocols. Ivan Ong, VP of R&D for Microban, said in a release that the new development will “help medical device manufacturers offer an antimicrobial solution that is more robust and provides more consistent antimicrobial performance.”

Wells Plastics, which claims to have been a specialist in antimicrobial additives for “many years,” says antimicrobial additives are currently providing protection in plastic films, fibers, and moldings, as well as powder coatings, adhesives, paper, and paints.
The company markets an additive called Bactiglas, saying that articles manufactured with the additive dispersions have been externally tested and proven to exhibit reductions in bacterial viable counts by as much as 99.9999% against controls. Bactiglas is a range of silver-based antimicrobial additive masterbatches and powder dispersions that uses a “microscopic glass-delivery system” for what it calls superior consistency and longevity of effect. In practice, Wells Plastics says that residual levels of atmospheric moisture combine with the hydrolytically reactive glass to release the silver ions at the surface of the component, killing bacteria.

The company notes that tests have shown the Bactiglas additive continues to work for at least eight years with no performance reduction. Wells says Bactiglas has successfully been incorporated into ABS, latex, PP, acetal, nylon, PPS, acrylic, PC, PSU, EVA, PE, PU, PS (high-impact and general-purpose), PEEK, PVC, and PET copolymers. The product is registered, and the active ingredient is approved through the EFSA and FDA as suitable for food contact. It also carries European BPD and U.S. EPA approvals.

Lower-cost protection
Biosafe Inc. says its antimicrobial additive provides permanent protection at a lower cost than conventional silver-based additives, while also eliminating problems like discoloration, opacity, and concerns about heavy metals. When incorporated into plastics compounds, Biosafe reportedly adds $0.25-$0.50 in raw material cost per pound of finished plastic product. By comparison, the company says antimicrobials based on silver-ion chemistry are usually incorporated at 1% levels and add $0.75-$1.50/lb in costs to end products.

Biosafe says its product takes 1-4 hours to achieve effective microbial reductions on plastic surfaces, compared to the more standard 24-hour test. Within plastics, Biosafe promoted its HM 4100 antimicrobial (read more about HM 4100), which the company supplies as a solid crystalline powder or in a masterbatch. Compounder RTP Co. produces the masterbatch for Biosafe using a silane-based technology vs. silver- or triclosan-based. The company says its products contain no volatile organic compounds, heavy metals, arsenic, or polychlorinated phenols.

The basic component in Biosafe products had been used for protecting textiles from microbial growth and was previously available only in a liquid solution. Biosafe was able to use organofunctional silane technology to convert its material into a dry crystalline powder that is thermally stable for use in extrusion and injection molding. —Tony Deligio