Last week I promised to take a look at soil and stain repellant finishes to see how each is applied and/or formulated. Some of these trademarked finishes claim impeccable green credentials, so it’s important that we are able to evaluate their claims – or at least know the jargon! The chemistry here, as I said in last week’s post, is dense. The important thing to remember about all these finishes is that they all depend on flurocarbon based chemistry to be effective.
The oldest water repellant finishes for fabrics were simply coatings of paraffin or wax – and they generally washed out eventually. Perfluorochemicals (PFC’s) are the only chemicals capable of repelling water, oil and other liquids that cause stains. Fabrics finished with PFCs have nonstick properties; this family of chemicals is used in almost all the stain repellant finishes on the market today. Other materials can be made to perform some of these functions but suffer when subjected to oil and are considerably less durable.
The earliest type of stain resistant finish (using these PFCs) prevented the soil from penetrating the fiber by coating the fiber. For use on a textile, the chemicals are joined onto binders (polyurethane or acrylic) that acts as a glue to stick them to the surface of the fabric. Gore Tex is one of these early coatings – a thin film was laminated onto the fabric; another, manufactured by 3M Corporation for nearly 50 years, is Scotchgard. Scotchgard was so popular and became so ubiquitous that “Scotchgard” entered the language as a verb.
The chemical originally used to make Scotchgard and Gore Tex breaks down into perfluorooctane sulfonate, or PFOS, a man-made substance that is part of the family of perfluorochemicals. PFOS and PFOA have chains of eight carbon atoms; the group of materials related to PFOA and PFOS is called C8 – this is often referred to as “C8 chemistry”.
An aside on C8 chemistry:
If you recall from last week’s post, the PFC family consists of molecules having a carbon backbone, fully surrounded by fluorine. Various “cousins” have carbon backbones of different lengths: PFOS or C8, for example, has 8 carbon atoms, C7 has 7, and so on. There is controversy today about the so-called “bad” fluorocarbons (C8 ) and the “good” ones (C6) which I’ll address below.
C8 – (the backbone is made of a chain of 8 carbon atoms): two methods are used to produce two slightly different products:
1) electrofluorination: uses electrolysis to replace hydrogen atoms in a molecule by fluorine atoms to create the 8 unit chain containing just carbon and fluorine. A small amount of PFOS (perfluorooctane sulphonate) is created during this process.
2) Telomerisation: chemical equivalent of making a daisy chain: produces mini polymers by joining single units together in chains. The usual aim is to produce chains that are an average of 8 units long, but the process is not perfect and a range of chain length will result – ranging from 4 units to 14 units in length. So you can have a C4, C6, C12, etc. In this method a small amount of byproduct called PFOA (perfluorooctanoic acid) is produced.
C6 – this chemistry produces a by-product called PFHA (perfluorohexanoic acid), which is supposed to be 40 times less bioaccumulative than PFOA. But it’s also less effective, so more of the chemical has to be used to achieve the same result. Manufacturers are trying to find smaller and smaller perfluorocarbon segments in their products, and even C4 has been used. The smaller the fluorocarbon, the more rapidly it breaks down in the environment. Unfortunatley, the desired textile performance goes down as the size of the perfluorocarbon goes down. “C6 is closest chemically to C8, but it contains no PFOA. It breaks down in the environment – a positive trait – but it doesn’t stick as well to outerwear and it doesn’t repel water and oil as well as C8, which means it falls short of meeting a vague industry standard, as well as individual company standards for durability and repellency.”
Back to Scotchgard:
Scientists noticed that PFOS (the C8 fluorocarbon) began showing up everywhere: in polar bears, dolphins, baby eagles, tap water and human blood. So did its C8 cousin PFOA. These two man-made perfluorochemicals (PFOS and PFOA) don’t decompose in nature. They kill laboratory rats at higher doses, and there are potential links to tissue problems, developmental delays and some forms of cancer. Below are tables of results which the U.S. Environmental Protection Agency released from data collected by 3M and DuPont; some humans have more PFOA in their blood than the estimated levels in animals in this study. For a complete review of this study, see the Environmental Working Group’s website, http://www.ewg.org/node/21726.
PFOA and PFOS, according to the U.S. EPA:
- Are very persistent in the environment.
- Are found at very low levels both in the environment and in the blood of the U.S. population.
- Remain in people for a very long time.
- Cause developmental and other adverse effects in laboratory animals.
Eventually 3M discontinued Scotchgard production. Yet accounts differ as to whether 3M voluntarily phased out the problematic C8 chemistry or was pressured into it by the EPA after the company shared its data in late 1999. Either way, the phase-out was begun in December 2000, although 3M still makes small amounts of PFOA for its own use in Germany. 3M, which still monitors chemical plants in Cottage Grove, Decatur, and Antwerp, Belgium, insists there are no risks for employees who handled or were exposed to the chemicals. Minnesota Public Radio published a timeline for milestones in 3M’s Scotchgard, which can be accessed here.
The phase-out went unnoticed by most consumers as 3M rapidly substituted another, less-effective spray for consumers, and began looking for a reformulated Scotchgard for carpet mills, apparel and upholstery manufacturers. For its substitute, 3M settled on perfluorobutane sulfonate, or PFBS, a four-carbon cousin of the chemical in the old Scotchgard, as the building block for Scotchgard’s new generation. This new C4-based Scotchgard is completely safe, 3M says. The company adds that it has worked closely with the EPA and has performed more than 40 studies, which are confidential. Neither 3M nor the EPA will release them.
According to 3M, the results show that under federal EPA guidelines, PFBS isn’t toxic and doesn’t accumulate the way the old chemical did. It does persist in the environment, but 3M concluded that isn’t a problem if it isn’t accumulating or toxic. PFBS can enter the bloodstream of people and animals but “it’s eliminated very quickly” and does no harm at typical very low levels, said Michael Santoro, 3M’s director of Environmental Health, Safety & Regulatory Affairs. 3M limits sales to applications where emissions are low.
3M says convincing consumers Scotchgard is safe is not its No. 1 challenge; rather it’s simply getting the new, new Scotchgard out. The brand, 3M maintains, is untarnished. “This issue of safety, oddly enough, never registered on the customers’ radar screen,” said Michael Harnetty, vice president of 3M’s protective-materials division.
Scotchgard remains a powerful brand: “We still get really good requests like, ‘Will you Scotchgard this fabric with Teflon?’ ” said Robert Beaty, V.P. of Sales for The Synthetic Group, a large finishing house.
Another early soil resistant finish is Teflon, which was produced by DuPont. Teflon is based on C8 chemistry, and PFOA is a byproduct of the manufacturing of fluorotelomers used in the Teflon chemistry.
There has been a lot of information on 3M, DuPont and these two products, Scotchgard and Teflon, on the web. The Environmental Working Group http://www.ewg.org/ has detailed descriptions of what these chemicals do to us, as well as the information on the many suits, countersuits, and research studies. The companies say their new reformulated products are entirely safe – and other groups such as the Environmental Working Group, question this assumption.
By the way, both DuPont and 3M advertise their products as being “water based” – and they are, but that’s not the point and doesn’t address the critical issues. In TerraChoice’s “Seven Sins of Greenwashing” this would be considered Sin #5: the sin of irrelevance, which is: “An environmental claim that may be truthful but is unimportant or unhelpful for consumers seeking environmentally preferable products. ‘CFC-free’ is a common example, since it is a frequent claim despite the fact that CFCs are banned by law.”
In January 2006, the U.S. Environmental Protection Agency (EPA) approached the eight largest fluorocarbon producers and requested their participation in the 2010/15 PFOA Stewardship Program, and their commitment to reduce PFOA and related chemicals globally in both facility emissions and product content 95 percent by 2010, and 100 percent by 2015.
The fluoropolymer manufacturers are improving their processes and reducing their waste in order to reduce the amount of PFOA materials used. The amount of PFOA in finishing formulations is greatly diminished and continues to go down, but even parts per trillion are detectable. Finishing formulators continue to evaluate new materials which can eliminate PFOA while maintaining performance but a solution is still over the horizon. One critical piece in this puzzel is that PFOA is also produced indirectly through the gradual breakdown of fluorotelomers – so a stain resistant finish may be formulated with no detectable amounts of PFOA yet STILL produce PFOA when the chemicals begin to decompose.
Recently a new dimension was added to stain resistant formulations, and that is the use of nanotechnology.
Nanotechnology is defined as the precise manipulation of individual atoms and molecules to create layered structures. In the world of nanoscience, ordinary materials display unique properties at the nanoscale. The basic premise is that properties can dramatically change when a substance’s size is reduced to the nanometer range. For example, ceramics which are normally brittle can be deformable when their size is reduced. In bulk form, gold is inert, however, once broken down into small clusters of atoms it becomes highly reactive.
Like any new technology, nanomaterials carry with them potential both for good and for harm. The most salient worries concern not apocalyptic visions, but rather the more prosaic and likely possibility that some of these novel materials may turn out to be hazardous to our health or the environment. As John D. Young and Jan Martel report in “The Rise and Fall of Nanobacteria,” even naturally occurring nanoparticulates can have an deleterious effect on the human body. If natural nanoparticulates can harm us, we would be wise to carefully consider the possible actions of engineered nanomaterials. The size of nanoparticles also means that they can more readily escape into the environment and infiltrate deep into internal organs such as the lungs and liver. Adding to the concern, each nanomaterial is unique. Although researchers have conducted a number of studies on the health risks of individual materials, this scattershot approach cannot provide a comprehensive picture of the hazards—quantitative data on what materials, in what concentrations, affect the body over what timescales.
As a result of these concerns, in September, 2009, the U.S. EPA announced a study of the health and environmental effects of nanomaterials – a step many had been advocating for years. And this isn’t happening any too soon: more than 1,000 consumer products containing nanomaterials are available in the U.S. and more are added every day.
And nanotechnology has been used for textiles in many ways: at the fiber as well as the fabric level, providing an extraordinary array of nano-enabled textile products (most commonly nanofibers, nanocomposite fibers and nanocoated fibers) – as well as in soil and stain resistance.
For scientists who were trying to apply nanotechnology to textile soil and stain repellency, they turned, as is often the case in science, to nature: Studying the surface of lotus leaves, which have an incredible ability to repel water, scientists noticed that the surface of the lotus leaf appears smooth but is actually rough and naturally dirt and water repellent. The rough surface reduces the ability of water to spread out. Tiny crevices in the leaf’s surface trap air, preventing the water droplets from adhering to the service. As droplets roll off the surface they pick up particles of dirt lying in their path. Using this same concept, scientists developed a nanotechnology based finish that forms a similar structure on the fibers surface. Fabrics can be cleaned by simply rinsing with water.
Nano-Tex (www.nano-tex.com) was the first commercially available nanoparticle based soil repellant fabric finish. It debuted in December of 2000. Another nanotech based soil repellant is GreenShield (www.greenshieldfinish.com) which debuted in 2007. Both these finishes, although they use nanotechnology, also base their product on fluorocarbon chemistry. Nano-Tex’s website does not give much information about their formulation – basically they only say that it’s a new technology that “fundamentally transforms each fiber through nanotechnology”. You won’t get much more in the way of technical specifications out of Nano-Tex. GreenShield is much more forthcoming with information about their process.
In the GreenShield finishes, the basic nanoparticle is amorphous silica, an inert material that has a well-established use in applications involving direct human consumption, and is generally recognized as safe and approved by the Food and Drug Administration (FDA) and Environmental Protection Agency for such applications. The use of silica enables GreenShield to reduce the amount of flurocarbons by a factor of 8 or more from all other finishes and it reduces overall chemical load by a factor of three – making GreenShield the finish which uses the least amount of these flurocarbons.
The GreenShield finish gets mixed environmental ratings, however. Victor Innovatix’s Eco Intelligent Polyester fabrics with GreenShield earned a Silver rating in the Cradle to Cradle program. However, the same textile without the GreenShield finish (or any finish) earned a higher Gold rating, reflecting the risk of toxicity introduced to the product by GreenShield. Information on product availability is at www.victor-innovatex.com.
 Bjorhus, Jennifer, “Scotchgard is Attractive Again”, St. Paul Pioneer Press, May 27, 2003