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Examining antimicrobial performance in textiles

November 4th, 2016 / By: / Feature

Martin Oeggerli, with support from School of Life Sciences.
Photo: Martin Oeggerli, with support from School of Life Sciences.

Textile testing was front and center at IFAI’s Advanced Textiles Conference and on the Expo show floor. Testing to be assured that a product will perform as expected is an important step in the development of any application; in antimicrobial performance, this is getting 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). Monticello encouraged the audience for his presentation to have results verified by a 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,” he 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?” asks Cristy Benson and Paul Sander, who are with UltraTech Intl. Inc. Aveho, which the company now has licensed from Kimberly –Clark, 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. Benson and Sander shared the podium in their presentation.

Aveho was designed to remove odors from three major chemical groups: sulfer (rotten eggs, wastewater 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, they said. “There is significant research on fabric being done,” they added.

Besides odor removal, repellency performance in fabrics has moved towards omni-repellency. The company’s product EverShield will repel food, mud, oil, dirt and other substances, but the company admits it’s not perfect. The big change for omni-repellency has been in the use of shorter-chain fluorine molecules: C6 rather than C8. Although a more effective chemical, C8 is no longer used because of environmental and health concerns. Trending now are CO’s that have no fluorine (C-Zeros), the presenters said.

Schoeller’s Nanosphere and DuPont’s Teflon are other examples of omni-repellent technology. They noted that compatibility between chemicals and a variety of fabrics is an issue.

Antimicrobials and minimizing uncertainties

In an Advanced Textiles Conference presentation titled “Antimicrobial Textiles: How to Evaluate and What Can Go Wrong,” Dave Klein of Thomson Research Associates 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 you to present a supporting report along with your goods.

The big question is, “How do you find a proper test?” He recommends talking to the associations that deal with testing and standards, such as ASTM International, AATCC (The American Association of Textile Chemists and Colorists), ISO (International Organization for Standardization) and others. But where to start? According to Klein, “Start by talking to the customer.”

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 says.

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 percent 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: ones with a quick turnaround, such as AATCC Test Method 30 that takes just a few hours, or ASTM G21, which 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 in other outdoor environments, there is currently just one commonly used test, which is from ASTM.

Compatibility with other treatments

Textiles face the “bioburden challenge,” says David Reed, PurThread Technologies, 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 said, 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 a lab coat from one room to another, which can increase the risk of spreading germs from one patient to another, or among healthcare workers. Beyond the healthcare setting, reusable fabric grocery bags could be carrying germs into consumers’ homes and back out again, when bags are reused for the next shopping trip.

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.