Examining antimicrobial and omni-repellency performance.
Textile testing was front and center at IFAI’s Advanced Textiles Conference and on the IFAI Expo 2016 show floor in Charlotte, N.C. Testing to be assured that a product will perform as expected is an important step in the development of any application; in antimicrobial performance, it is becoming even more complex.
Whatever the goal in testing, “The key is to have a defendable technology … that shows real-world performance,” says Robert Monticello, Ph.D., senior scientific advisor with the International Antimicrobial Council (IAC), Washington, D.C. Monticello encouraged the audience for his presentation to have results verified by an outside resource, such as the IAC’s Verification Program.
It’s not always that straightforward, however—particularly when the product’s goal is odor control. An “artificial nose” is on everyone’s radar, but one that is sensitive enough has yet to be developed, and “the equipment to make it is very expensive,” Monticello says.
There are professional “odor sniffers,” but people and their ability to smell is quite subjective. In fact, some people like a smell that others find distasteful.
“Antimicrobials can kill microbes that create odor, but what about odors that don’t come from microbes?” ask Cristy Benson and Paul Sander with UltraTech International Inc., Jacksonville, Fla. BensonandSandersharedthe podiumin theirpresentation. Aveho®, which the company now has licensed from Kimberly–Clark Corp., Dallas, Texas, was a technology developed to make odor-free diapers, but it was not successful in that application because parents didn’t want that capability in their babies’ diapers.
Aveho was designed to remove odors from three major chemical groups: sulfur (rotten eggs, waste water smells), nitrogen(urine, ammonia) and oxygen(body and foot odor). While there has been progress and testing in non-fabric markets, initial testing began on cotton and was successful, Benson and Sander said. “There is significant research on fabric being done.”
Besides odor removal, repellency performance in fabrics has moved toward omni-repellency. UltraTech’s product EverShield® was designed to be an omni-repellent fabric. It will repel food, mud, oil, dirt and other substances, but it is not perfect. The big change for omni-repellency has been in the use of shorter-chain fluorine molecules: C6 rather than C8, which is a more effective chemical but is no longer used because of environmental and health concerns.
Schoeller’s Nanosphere® and DuPont’s Teflon™ are other examples of omni-repellent technology. Benson and Sander noted that compatibility between chemicals and a variety of fabrics is an issue.
Trending now are COs that have no fluorine (C-Zeros). Carlo Centonze, CEO of HeiQ, Bad Zurzach, Switzerland, and a presenter at IFAI’s Advanced Textiles Conference, told his audience, “Nature can teach us a lot about water repellency.” The textile industry continues to explore fluorine-free options by studying nature. “The structures of a tree leaf and a butterfly wing present excellent examples of water repellency,” he added.
In an Advanced Textiles Conference presentation titled “Antimicrobial Textiles: How to Evaluate and What Can Go Wrong,” Dave Klein of Thomson Research Associates, North York, Ontario, Canada, told his audience that antimicrobial treatments on textiles are unlike almost all other finishes. “It’s a bit of a leap of faith on behalf of both the producer and consumer,” Klein said.
The best you can do, he added, is to find a reproducible and relevant lab test, which usually involves a third party. This is important because it allows a company to present a supporting report along with the products.
The big question is, “How do you find a proper test?” Klein recommends talking to the associations that deal with testing and standards, such as ASTM International, AATCC (Association of Textile, Apparel & Materials Professionals, formerly The American Association of Textile Chemists and Colorists), ISO (International Organization for Standardization) and others. But where to start? “Start by talking to the customer,” said Klein, in order to be very clear about the customer’s end product performance expectations and requirements.
TYPES OF TESTING
Bacterial testing, for example, falls into two types: those that use qualitative methods and those that use quantitative methods. Qualitative methods (such as AATCC TM 147) are quick, easy and relatively cheap to do, providing results in just a day. Since this is a “yes/no” method, it’s not particularly sensitive and, therefore, not appropriate for many newer “actives,” so it’s less common than a decade ago, Klein said.
Quantitative methods offer many options and will vary, but they follow the same general method. An actual number is provided in the results, usually expressed as a percentage or log (number) reduction. There isn’t necessarily a “pass/fail,” so those using the test will have to consider end uses for their product and decide what they want to say about the product when evaluating the testing results.
There are similar options for fungal testing: those with a quick turnaround, such as AATCC Test Method 30 that takes just a few hours, or ASTM G21, a test that takes about four weeks but is often the go-to test and may be best for outdoor materials.
For the pink stains caused by bacteria and found in marine vinyl and foam, tarps, awnings and other outdoor environments, there is currently just one commonly used test, from ASTM.
Textiles face the “bioburden challenge,” said David Reed, PurThread Technologies Inc., Cary, N.C., because the risk of infection with textiles is more significant than with other surfaces. PurThread uses Kodak’s EPA-registered silver salt at the fiber stage of textile production, creating non-toxic, multi-modal, broad-spectrum protection against germs, Reed says, because it is an imbedded technology, rather than coated or topical. The company uses recycled silver and micro-sized particles, not nano-sized, he added.
More applications are being considered. For example, medical personnel usually wear lab coats, which can spread germs. Beyond the health care setting, reusable fabric grocery bags can carry germs into consumers’ homes and stores. Scientific publications will be released soon about the use of the product in these two new applications.
Janet Preus is senior editor of Advanced Textiles Source.