Protection from an unseen foe

Because the inherent makeup of textile structures provides an attractive environment for microorganisms, antimicrobial technologies are an important consideration for many textile applications.

We live in a world of microbes: most are helpful; some are harmful. Microbes, in fact, outnumber all other species, yet only 3 percent are harmful and only a tiny fraction have been identified. Microorganisms include bacteria, viruses, fungi and algae, but only the first three involve textiles. Protecting from harmful microorganisms, while not hurting the beneficial ones, is a daunting task, but it offers real opportunity in the advanced textiles industry.

The basics

1. Antimicrobial is a generic term for those chemicals and treatments that kill (biocidal) or inhibit (biostatic) the growth of microorganisms. Antimicrobial agents function in different ways:
2. Metals and metal salts rely on the penetration of cell walls to deactivate proteins and kill bacteria. Silver, copper, and zinc are examples.
3. Quaternary ammonium salts effect membrane damage and prevent reproduction and growth. These are widely used.
4. N-Halamines have oxidative properties, which include chlorine compounds, such as bleach.
5. Organic molecules, such as triclosan, and natural substances, such as chitosan derived from crustacean shells, are growing in use.

Delivery technologies include internal where the antimicrobial (i.e., silver) is integrated into the fabric; surface application, though durability in washing can sometimes be a problem; and chemical bonding of the antimicrobial to the fiber/fabric.

Antimicrobials that are integrated into or chemically bonded to the fibers and are essentially permanent (nonleaching) and biostatic kill the threats. Other delivery methods utilize controlled release mechanisms effective on microbes on the fiber or fabric surface. These may be more easily washed off and may leach into the environment, creating problems in wastewater and sewage or with desirable plants and agricultural environments. Such antimicrobials are biostatic: they stop the pathogen, preventing it from penetrating, thereby depriving it of the ability to grow, which causes it to die off.

Primary functions

Antimicrobials fall basically into two areas: protecting from harmful microbes and preventing their spread, and preventing staining or degradation. Both may involve controlling odors, one of the major factors driving their increasing usage. Desirable antimicrobials are durable with regular washing and wear; are nontoxic to humans; can be easily incorporated with conventional textile equipment and processes; are compatible with other treatments, such as water and fire repellents; resist leaching; and cause no environmental damage—all at reasonable cost.

Concerns

As the usage of antimicrobials proliferates, the developing resistance to antibiotics and disinfectants used to control them is troubling. New formulations and chemistry must be developed to overcome such resistance.

If you are looking to incorporate antimicrobials into your products, take the time to familiarize yourself with antimicrobial technology so you are sure to utilize the right compound(s) and the right delivery system for the intended use. It is also critical to understand U.S. Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) regulations, as well as state regulations. EPA approval is required for most items, and FDA for many. Claims in promotional materials and advertising concerning what a product are also carefully regulated.

Limited clinical trials and lab tests are routinely done in the development of new antimicrobials and provide good insight about their efficacy. The burden of proof lies primarily with the producer of the chemistry.

How much

Curt White of White IEQ Consultants LLC, Midland, Mich., says that it’s difficult to assess the size and growth potential for the antimicrobials segment that uses textiles. The active ingredients that carry the needed registrations, he says, are sold to formulators or sub-registrants who sell them to textile chemical distributor/service companies, who sell to the mills. The mills sell to the retailers, brand-name companies and the open consumer sales marketplaces. Most of the brand-name antimicrobial companies are doing pull-through selling directly to the brand-name companies and major retailers.

Most of the active ingredient producers are private or so big that their data on antimicrobials for textiles is either confidential or masked inside of numbers for other uses. However, survey services (Frost and Sullivan, The Freedonia Group, Research Markets) have done a good job estimating numbers. Their reports provide a useful perspective on the industry for anyone seeking to enter the market.

The Freedonia Group, Cleveland, Ohio, covers the total disinfectant and antimicrobial market, not just for textiles. Its June 2013 report, “Disinfectant and Antimicrobial Chemicals to 2017,” projects that total U.S. demand should rise 6.1 percent annually, reaching $1.6 billion in 2017. This is a significant growth rate from previous years, due primarily to a rebound of construction and strong gains in industrial markets such as paints and plastics. However, there is also huge growth in consumer goods that include antimicrobials for odor control and aesthetics, so their inclusion in materials for sports and leisure apparel and equipment will drive the market. With growing concerns over antibiotic resistance, an aging population requiring growing health care and medical applications, and an increase in the number of people pursuing exercise and sports activities, antimicrobial usage in textiles will increase.

Given the  complexity and the convoluted supply chain, White feels the value of the antimicrobial products used for aesthetic reasons (microbial odor or stain control) and performance reasons (deterioration/preservation or rotting), is difficult to ascertain. In aggregate, and looking just at chemical value, White thinks sales in the $40-70 million range of chemicals sold to the mills would be likely. There is an unlimited potential for the finished product at retail, reaching several hundred million dollars.

The silver controversy

Silver is a widely used antimicrobial, most often impregnated into the fiber when spun or into the yarn or fiber when made. It is highly effective and used extensively in a variety and growing number of products. Several forms of silver may work, but they only work if ions are given off.  How silver is incorporated into fabric and the mechanism of ion release are the keys to its success.

The use of silver has come under some scrutiny. Simply put, silver ions are given off when contact is made with humidity under the right conditions: they penetrate the microbe cell walls like a sword, killing the pathogen. The silver ions actually do the killing of microbes and bacteria. Silver itself is essentially inert with only low levels of ions given off and only under specific conditions.

Some feel that silver ions can penetrate into the skin; others are concerned that the silver, especially nanosilver, may leach off and get into the ground and harm useful microbes. Much research is being done in the U.S. and Europe with results open to interpretation, but nothing conclusively proves that silver harmful when it’s used properly.

Many silver proponents are working on ways to further ensure that silver does not cause unintended results, and a number of new products are evolving. Also, as effective as silver can be, it has a slow inhibition/kill rate, many interfering organic and inorganic materials, and its impact on humans and the environment from manufacturing to disposal needs to be considered for each intended use. White explains that silver-based antimicrobial suppliers have modified the size of the silver salt particles and developed unique delivery formulations that overcome some of the in-manufacturing handling and in-use and abuse utility and efficacy issues.

He says, “Beyond cost and service, textile people need to take a stewardship view of their antimicrobial choices, including the silver-based products, with emphasis on four pillars.” These are:

1. Regulatory compliance for the specific use and claims made. This may be a U.S. EPA, including [individual] states or FDA jurisdiction, or under the jurisdiction of the European Union (EU) or other global area governmental agencies.
2. Safety. Impact on people and the environment from manufacturing to end use and abuse to disposal.
3. Performance for the intended uses and abuses accounting for the claims to be made, the target organisms, the rate of inhibition or kill, the interfering physical conditions (temperature and moisture), organic materials (blood, skin, plant materials, dead microbes), inorganic materials (red-ox materials, counter ions) and pH conditions through use and disposal.
4. Costs and services any one supplier might provide in the region of manufacturing and the region of sale and use.

White stresses that silver, like any antimicrobial, must be considered as a tool—one of many—and utilized in specific ways that are appropriate.

When selecting which antimicrobial to use, including silver, White says there are four basic issues to address:

1. What is the end use? Each end use has its own requirements.
2. What abuse might it receive outside the intended application? Heavily chlorinated water and other pollutants may degrade the silver used in filtration, making it useless and even possibly harmful.
3. What do you want it to do or what claims do you wish to make? Claims are strictly regulated.
4. What are the regulatory issues? The EPA, FDA, and some state regulators must be consulted and their requirements met before using any antimicrobial in fabrics. The toxicology and chemical issues should be reviewed, as well as what recycling and sustainability issues may be involved.

Markets

Health, hygiene and medical areas are growing fields, especially as people age and need greater care. The fast growth of nursing homes and assisted living facilities presents opportunities.

Health care items include scrubs and other worker garments, cubicle curtains, medical office and waiting room furniture, bedding, and incontinence and hygiene items. Reducing contamination risks and infection is a high priority for health care providers.

More consumer products are incorporating antimicrobial protection, particularly for odor control, in clothing, shoes and personal hygiene items.

The military, emergency service providers, fire and police services also have uses for antimicrobial textile products. Work wear in many industrial areas and in food processing are requiring uniforms and garments with antimicrobial protection that does not affect the physical properties of the garment.

Filtration accounts for substantial usage of antimicrobials, from home water filtration to filters used in large commercial operations. Automotive uses, such as cabin filters, are growing. Even tiny filters in medical devices are widely used. HVAC systems use filters to clean the air in homes and public buildings.

And the ubiquitous disposable nonwoven wipes for personal and home use have antimicrobial properties.

Sources

The antimicrobial industry involves companies of all sizes. Vestagen Technical Textiles LLC, Orlando, Fla, has recently introduced Vestex®, a composite product employing a three-way approach: a barrier so bodily fluids easily roll off and don’t accumulate; an impregnated antimicrobial to fight odors and pathogens on the outside surface of the composite; and a fabric with a high moisture vapor transmission rate. This allows wicking and transporting moisture from the skin to the fabric and through the surface, which cools the body and prevents larger sweat droplets from going through. The technology allows the fabric to remain clean and fresh.

Based on Swiss technology and U.S.-based research, it includes a fluorine/silicon oxide technology for a self-cleaning fluid barrier surface and a silane-based quaternary ammonium chloride antimicrobial. Ben Favret, president and CEO, says the fabric retains its softness and comfort while killing pathogens and keeping the wearer cool. Favret is adamant that antimicrobial fabric treatments without a fluid barrier are not sufficient, including silver.

“No antimicrobial can kill fast enough to prevent fluids in the quantities that are prevalent in health care,” Favret says. The cooling effect also is important to keep the health worker comfortable. A three-way approach, he feels, is essential. “Any place where people can be exposed to contamination or co-exist in close quarters would be candidates for this technology, as infection is easily spread,” he says.

Dow Chemical’s Dow Microbial Control business unit is an example of a larger company with extensive experience and resources focusing on new delivery systems. It has recently announced a silver-based antimicrobial, SILVADUR™ Antimicrobial. According to its manufacturer, it is the only silver-based antimicrobial technology that employs an organic polymer system to deliver low concentrations of silver ions to fabric surfaces. Dow offers standard formulations and applications that can be used by many, while retailers and brand managers can design combinations unique to them to provide protection and freshness in products with durable launderability. (For more about this technology, see “The Polymer Approach” on this site.)

Microban International Ltd., Huntersville, N.C., has built a global brand with its antimicrobial products ranging from soft products such as textiles, sports equipment and apparel, to hard surfaces like countertops, appliances and bathroom surfaces. The company formulates organic and inorganic antimicrobial technologies for a variety of applications and its line ranges from liquids to polymers to ceramics. Microban is unique in this regard.

Sciessent, Wakefield, Mass., maker of the Agion® line of antimicrobials, uses silver, copper and zinc in customer-specific requirements.

Noble Biomaterials Inc., Scranton, Pa., producer of X-Static®, is a global player with a multifunctional line of antimicrobials. X-Static bonds silver to the surface of the fiber. In addition to antimicrobial performance and odor fighting issues, Noble claims a cooler garment because the silver surface reflects heat. The items can also be conductive.

Unifi Inc., Greensboro N.C., produces a range of polyester and nylon filament yarns with special features, including some from recycled PET and others with antimicrobial features. This longtime producer of silver-impregnated polyester yarns can custom design them for end user needs.

If you are looking for something new for your product, you may find it useful to check with university research facilities. Many are working in this field, and much of that work is available for licensing through their technology transfer operations. Some may even offer incubator programs to assist companies in utilizing the research.

Making a move

The antimicrobial field is growing rapidly and offers substantial opportunities. Products with antimicrobial protection often have a marketing edge and may command higher prices and better margins. Both small and large companies are announcing new products regularly. Often these products have a special twist, usually on the delivery system, making them more effective and desirable.

Working with an alliance partner (most often the antimicrobial producer) is a good way to explore integrating antimicrobials in the line of products you offer. Antimicrobial producers can work with you on a product with specific attributes, allowing it to have a unique niche in the marketplace. As in any field of technical textiles, especially advanced textiles, the key is to do your research.

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William C. Smith is a technical textile consultant.