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'Greener' Stain-resistant Coatings Developed

September 20, 2005
American Chemical Society
When it comes to fighting stains, "greener" is better. Chemists at the University of North Carolina at Chapel Hill say they have developed an alternative material for making stain-resistant coatings that does not lead to the production of PFOA, a pervasive chemical that has been termed a "likely carcinogen" by an EPA advisory board. Their study will be presented on August 29th at the national meeting of the American Chemical Society in Washington, D.C.

WASHINGTON — When it comes to fighting stains, "greener" isbetter. Chemists at the University of North Carolina at Chapel Hill saythey have developed an alternative material for making stain-resistantcoatings that does not lead to the contamination of the environmentwith PFOA, a pervasive chemical that has been termed a "likelycarcinogen" by an EPA advisory board.

PFOA (perfluorooctanoicacid) is used directly in the manufacture of the coatings used innonstick cookware and is also produced by the gradual breakdown in theenvironment of stain-resistant coatings on clothing and paper goods.Both materials, which have similar properties, are manufactured under avariety of brand names. A growing number of researchers believe thatfabric-based, stain-resistant coatings, which are ubiquitous, may bethe largest environmental source of the controversial chemical.

Thenew materials use a novel type of short-chain fluorocarbon that doesnot degrade into PFOA and is less likely to cause health effects, theUNC scientists say. The greener compounds are primarily intended toreplace conventional stain-resistant coatings that are now used inclothing and packaging that eventually degrade into PFOA, they say. Thecompounds are not designed to replace the coatings used in nonstickcookware that are manufactured using PFOA, the researchers point out.Their finding was described today at the 230th national meeting of theAmerican Chemical Society, the world’s largest scientific society.

"Thesenew compounds can go a long way toward reducing PFOA in the environmentwhile still providing the convenience of stain-repellant coatings,"says study leader Joseph M. DeSimone, Ph.D., a chemistry professor atUNC and director of the National Science Foundation (NSF) Science andTechnology Center for Environmentally Responsible Solvents andProcesses. "That’s good news, because once PFOA gets in the environmentand in the body, it tends to stay there."

An estimated 95 percentof people in the United States have the chemical in their blood,according to the Centers for Disease Control and Prevention (CDC). Butscientists are not sure how the chemical is getting into the body andhave limited information on its long-term health effects.

PFOA,also known as C8, is a man-made chemical that has been used for almost40 years in a variety of commercial applications. The compound is usedin the manufacture of fluoropolymers, which are used to make nonstickmaterials that are used in some cookware, according to the researchers.The compounds are not present in the nonstick coating itself, they add.

PFOAis also produced indirectly through the gradual breakdown offluorotelomers, compounds that are used to provide water, stain andgrease resistance to many fabric and paper goods, such as clothing andfood packaging. Because stain-resistant coatings are so widely used,many researchers believe that these coatings may be a larger source ofPFOAs than the manufacture of nonstick materials, DeSimone says.

Fluorotelomersare long-chain (eight carbon) compounds that tend to form a protectivelayer on fabrics and paper goods that are coated with the compounds.Over time, oxidation can cause the fluorotelomers to degrade to PFOA,which is difficult to break down due to its durability and bondstrength. PFOA also has a tendency to accumulate in cells due to itspolarized structure, which has both hydrophobic (water-repelling) andhydrophilic (water-loving) parts, similar to the cell membrane, theresearchers say.

DeSimone and his associates, Paul Resnick,Ph.D., and graduate student Ji Guo, designed a group of shorter,four-carbon fluorotelomers, called "C4 plus" that are less bulky thanthe longer chain fluorotelomers. The newer compounds do not producePFOA and do not appear to be capable of accumulating in the body uponoxidation. In early laboratory tests, coatings made with the new C4plus compounds performed as well as or better than the conventionalcoatings, the researchers say.

The researchers have filed apatent for these new materials, which they say have the same beneficialproperties as conventional coatings and can easily be scaled up toindustrial standards. Several textile companies have expressed aninterest, DeSimone says. His study is funded by NSF.

The findingrepresents another environmental achievement for DeSimone’s researchgroup. Several years ago, the researchers found a way to manufacturemany different fluoropolymers in supercritical carbon dioxide thatavoids the use of PFOA. DeSimone received a Presidential GreenChemistry Challenge Award in 1997 for developing this process. Like C4plus, this process also shows great potential for reducing PFOA in theenvironment, particularly in the manufacture of nonstick coatings usedin cookware, the researcher says.

"The high quality of JoeDeSimone's science is well-established as a Presidential GreenChemistry Challenge Award winner," says Paul Anastas, Ph.D., directorof the ACS Green Chemistry Institute. "It takes that high-qualityscience to address one of the great chemistry challenges of our time:designing our molecules so that they do not persist and bioaccumulatein humans and in the environment."

The American Chemical Societyis a nonprofit organization, chartered by the U.S. Congress, with amultidisciplinary membership of more than 158,000 chemists and chemicalengineers. It publishes numerous scientific journals and databases,convenes major research conferences and provides educational, sciencepolicy and career programs in chemistry. Its main offices are inWashington, D.C., and Columbus, Ohio.

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