Cotton Products Research: Durable Press and Flame Retardant Cotton

National Historic Chemical Landmark

Designated May 14, 2004, at the United States Department of Agriculture ARS Southern Regional Research Center in New Orleans, Louisiana.

Commemorative Booklet (PDF)

Easy care cotton fabrics are now common. Much of the research in developing processes that led to and improved the quality of durable press fabrics was carried out at the Southern Regional Research Center in New Orleans. Scientists at this U.S. Department of Agriculture facility have provided the understanding of the mechanisms that impart durable press to cotton. At the same time, SRRC researchers have made significant strides in developing durable flame retardant finishes for cotton fabrics.

Contents

“The Evolution of Durable Press and Flame Retardant Cotton” commemorative booklet
“The Evolution of Durable Press and Flame Retardant Cotton” commemorative booklet produced by the National Historic Chemical Landmarks program of the American Chemical Society in 2004 (PDF).

Cotton and Chemurgy: Stemming Cotton's Decline by Developing New Uses

King Cotton was about to be dethroned. By the middle of the 20th century, synthetics were usurping cotton as the dominant textile. Wrinkle resistant synthetics had captured a large part of the clothing market and had begun to be used in household items traditionally made of cotton.

Cotton is a natural seed fiber that exhibits many attractive qualities. It is comfortable; it breathes; and it can be dyed easily. These traits combined with its wide availability and renewability made cotton desirable for apparel and home use for centuries. As late as 1960, cotton accounted for two-thirds of the total retail apparel and home furnishings market (excluding carpet). Over the next fifteen years the onslaught of synthetics reduced cotton to a one-third share of that market, and projections in 1975 showed that if the rapid decline in consumer demand continued, cotton would be able to claim only 20% percent of the retail market.

Cotton's projected decline would have meant there would be little cotton grown in the United States by the end of the century. This was the situation that scientists and researchers at the United States Department of Agriculture ARS Southern Regional Research Center faced when they began studies designed to make cotton competitive with synthetic fabrics. And one measure of their success is that by 2000 cotton owned a 61.5% share of the retail market for apparel and home furnishings (again, excluding carpet). In that year, cotton comprised 76% of all textiles used in men's apparel, and the average consumer used thirty-seven pounds of cotton a year, half again as much as ten years previously. King Cotton was reclaiming his throne.

Cotton farming in the early years of the 20th century, like much of U.S. agriculture, suffered from overproduction, a chronic problem that resulted in surpluses and low prices. In a sense, the American farmer was the victim of his own success as mechanization and newer and better crop varieties increased yields per acre. After World War I agricultural problems worsened. In the 1920s farmers were buffeted by inflation. Then the Great Depression, an era of deflation and lower and lower commodity prices, forced many off the land and impoverished those who stayed.

Record agricultural production combined with declining demand spurred the growth of the chemurgy movement ("chem" from chemistry; “urgy,” Greek for work), which was composed of scientists, agriculturalists, and industrialists determined to put chemistry to work to find nonfood uses for agricultural surpluses. The public voice of this movement was the Farm Chemurgic Council which had the support of Henry Ford and Irenee DuPont and which bombarded Congress with its message that through research new industrial products would be developed from farm commodities.

Congress was receptive to this message because of the excellent track record of the U.S. Department of Agriculture in sponsoring research. USDA scientists made many significant advances in the decades after the department's creation during the Civil War, and numerous subsequent agricultural adjustment acts established experimental stations and research laboratories around the country. These facilities proved their value by developing new uses for agricultural products.

The crop surpluses, the influence of the chemurgy movement, and the USDA's research record encouraged Congress, in a small part of the 1938 Agricultural Adjustment Act, to instruct Secretary of Agriculture Henry Wallace "to establish, equip, and maintain four regional research laboratories, one in each major farm producing area, and at such laboratories to conduct researches into and to develop new scientific chemical and technical uses and new and extended markets and outlets for farm commodities…" A subsequent law directed the USDA to conduct a survey to determine the best locations for the regional laboratories and to recommend areas of research for each.

The four sites chosen were Philadelphia, the San Francisco Bay area, Peoria, Illinois, and New Orleans. Congress appropriated four million dollars to build and equip the laboratories, and sites were quickly obtained. In New Orleans, the site was a swampy part of City Park near Bayou St. John. The New Orleans municipal government donated the land to the USDA. Contracts for construction were let quickly, and by early 1941 all the buildings at all four sites had been completed and equipped, and the first scientists were hired and on the job doing research.

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"Chemical research at this laboratory [Southern Regional Research Center] on 'durable press/easy care' and 'flame retardancy' has been extremely significant for increasing cotton markets and market share and helping cotton compete against synthetic fibers."
— Phillip J. Wakelyn, Senior Scientist, National Cotton Council

Establishment of the Southern Regional Research Center

The first director of the New Orleans facility, Daniel F. J. Lynch, said in 1939 that "one important line of attack [to solve the surplus problem] is by means of research… carried on with the specific aim of finding new and extended uses for farm commodities. We believe that research of this nature will pay (not immediately of course—that would be too much to hope for) but more and more with the passing of each year. We believe, moreover, that such a program is long overdue." Each center was commissioned to focus on problems affecting crops in its region: For the southern center, that meant sweet potatoes, peanuts, and cotton—especially cotton. In the 1950s and 1960s, for example, as much as 80% of the budget was on cotton research. "Not how to grow cotton," says Clark Welch, a scientist at the SRRC for 46 years. "I don't know a thing about that, but how to chemically process it to make it suitable as a flame retardant and wrinkle resistant material."

Charles H. Fisher was the director of the SRRC from 1950 to 1972, when much of the important early research into the chemical modification of cotton took place. Many of the scientists who worked there then and later—the lengthy tenure of so many of the researchers at SRRC is striking—speak highly of Fisher as an administrator. Robert Reinhardt, for example, says "I think Dr. Fisher was a great director… getting us the materials we wanted and the money from Washington. He was very, very good at that." Another SRRC veteran, Ruth Benerito, points out that "the 50's was the golden age of science, when they put a lot of money into science because we were competing with Sputnik. Wherever you were, it was a good time to be in science." She adds that the administrators in Washington, who decided what research would be done and allocated resources, were all scientists: "That was before the days of the Harvard School of Business Administration."

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Development of Durable and Wrinkle-resistant Cotton

The urgency to produce wrinkle resistant or durable press cotton garments came with the introduction of synthetic fibers. But even before nylon and polyester, chemists experimented with ways to treat cotton with agents that would impart wrinkle resistance. In the early years of the 20th century, French chemists studied the reaction of formaldehyde with cotton. Then British scientists at a textile finishing company tried to make cotton exhibit the qualities of wool.

Cotton is a natural fiber composed mainly of cellulose, which is a polymer. The cellulose chains in cotton, composed of microfibrils, have only hydrogen bonds between them, so there are no covalent crosslinks to force the cellulose chains to return to their original position when deformed by wrinkling or laundering. In the late 1950s, SRRC scientists initiated work on wrinkle resistance so that fewer wrinkles would form and those that did would fall out on hanging. In other words, the cotton would recover, much like wool does. The next stage was wash and wear: making a wrinkle free garment that would come out smooth after washing. But wash and wear had a problem; it would not hold a crease. That led to the next stage, sometimes called permanent press, but more accurately termed durable press, in which wrinkle resistance and durable creases could be achieved in cotton garments.

In the beginning, scientists used urea-formaldehyde resins, which are relatively inexpensive, to produce cotton garments that had wrinkle resistance and shape retention. Later, melamine-formaldehyde condensates exhibiting improved properties were introduced. SRRC scientists understood in the early years of research that wrinkle resistance could be imparted to cotton by polymer forming reagents and surface treatments, but that better and more durable levels of wrinkle resistance could be achieved when the reagents actually penetrated the fibers and reacted with the cellulose. The result was a chemical modification of the fabric by crosslinking. This means that the cellulose molecules, which are long chains, are chemically linked by short molecules to make them more rigid and the fabric wrinkle resistant. The crosslinks between cellulose molecules are analogous to the rungs on a ladder. Fabrics treated with these formaldehyde resins when smooth will return to smoothness when washed.

Over the years, SRRC scientists experimented with new finishing agents with the goal of trying to reduce the amount of the formaldehyde used in durable press processes because of safety concerns. Formaldehyde derivatives were commonly used because they are cheap and highly effective as a wrinkle proofing agent. Formaldehyde derivatives are fine reagents, except that they are not stable. This means there is a very slow release of formaldehyde during processing in the mill and during storage of the treated fabric or finished garment. Formaldehyde release raised safety concerns, so over the years SRRC scientists worked to control the amount of formaldehyde released in durable press processes.

Researchers succeeded in reducing the amount of formaldehyde released from three thousand parts per million to about 250 parts per million, which, according to Bethlehem Andrews, "is almost negligible, and at that point, you can hardly reduce it more." Better preparation of the finishing agents helped lower formaldehyde release, but finding newer and more stable finishing agents proved the best method. The major success in this area came with the introduction of DMDHEU (dimethyloldihydroxyethyleneurea), or more correctly 1,3-bishydroxymethyl-4,5-dihydroxy-2-imidazolidinone. DMDHEU was first patented by BASF, but SRRC scientists researched capping agents added in the crosslinking process that further lowered the formaldehyde release.

Of course, eliminating formaldehyde altogether became a goal. While some successes were achieved in finding formaldehyde-free reagents, there were problems. The formaldehyde-free reagents are more expensive and many of them cause discoloration. Some have toxicity problems of their own. One safe but relatively expensive reagent, DHDMI [dihydroxydimethylimidazolidinone (1,3-dimethyl-4,5-dihydroxy-2-imidazolidinone)] produced moderate levels of resilience and is used in infants' clothing. Polycarboxylic acids are the most successful of the non-formaldehyde agents, particularly BTCA (butanetetracarboxylic acid). SRRC scientists discovered a series of catalysts to enable these acids to react with cotton fabrics to achieve the crosslinking needed to impart durable press properties. The greater cost of formaldehyde-free agents, however, has limited their commercial adoption.

In addition to safety concerns, there were other problems with the finished cotton treated with nitrogenous formaldehyde-based substances. The main problem was chlorine absorption. The garments treated with melamine-based finishes would turn yellow. The urea-type finishes would retain chlorine and, in the words of Robert Reinhardt, an SRRC scientist, "if they were subjected to heat, a touch-up ironing, the chlorine would be released and generate acid and seriously diminish the strength of the fabric."

Another problem with formaldehyde treatments was strength loss, which is called "crosslink embrittlement." The goal in all treatments was to achieve a smooth appearing fabric that was not so weak it would fall apart. In some of the formaldehyde treatments, as Noelie Bertoniere says, "if you bent forward your shirt would have split up the back, and that's not acceptable." Or, as Reinhardt says, "if you have too many crosslinks in there, it's like a lead pencil, it won't bend, it'll break." This is still a major aim of the textile industry: To come up with a wrinkle free treatment that does not cause the fabric to lose strength. As another researcher, John Frick, put it: "The end of all, which we could never quite reach, was to do the finishing without damaging the strength and the wear resistance of the cotton." A related aim is to improve the wear life of a garment, so that, for example, cuffs do not fray.

Many approaches were taken to solve these problems. One avenue was to blend cotton with polyester which produced a stronger fabric but not a stronger crosslinked cotton component. SRRC researchers also explored additives which did not chemically attach to the fibers. One such additive was emulsified polyethylene, patented by Reinhardt, which stays on the surface and essentially protects the surface from wear. Polyethylene softens cotton fabric, gives it more strength, and increases abrasion resistance substantially. It is also inexpensive and remains much in use.

Durable press has helped to revive the cotton textile industry. Much of the work in improving durable press, in discovering crosslinking mechanisms and additives to improve those mechanisms, was done at the Southern Regional Research Center. But imparting wrinkle resistance without losing strength while at the same minimizing abrasion remains the primary research objective for the cotton fabric industry.

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Development of Flame Retardant Cotton

The danger posed by combustible textiles fueled the search for flame resistance. As early as 1735, Obadiah Wyld received a patent in Great Britain for developing a flame retardant mixture of alum, ferrous sulfate, and borax. Studies continued in the 19th century in which various agents were used in the search for flame resistance. While some success was achieved, most attempts eventually failed because most of the agents, often inorganic salts, were water soluble and would wash out of the fabric. The one exception was the work of chemist William Henry Perkins who developed the "Non-flam" process using stannic oxide. In 1912 he claimed that garments treated with stannic oxide were flame resistant and stood up to two years of use with weekly washing.

The initial impetus for research at the Southern Regional Research Center into flame resistant cotton fabrics came from the Army's Quartermaster Corps, which was seeking fire retardant uniforms. At the same time, people in the cotton industry understood that there would be consumer demand for flame retardant textiles if they could be made durable and if the fabrics could overcome the stiffness and roughness that characterized early attempts.

Research at SRRC focused on the chemical modification of cotton by the chemical reaction of flame retardants with the cellulose molecules on the surface and within the cotton fiber. Wilson Reeves and J.D. Guthrie led research into the durable flame retardant tetrakis(hydroxymethyl)phosphonium chloride (THPC), which unfortunately had the disadvantage of a significant loss in fabric strength. To counter this problem, scientists raised the pH of THPC with aqueous sodium hydroxide, creating THPOH [tris(hydroxymethyl)phosphonium hydroxide]. This process resulted in fabrics which were less stiff and stronger. THPC and THPOH were both treated with bromine compounds and ammonia in an attempt to produce flame retardant fabrics that were light weight and had a good "hand," that is, they were soft to the touch.

Other additives that were used included APO [tris(aziridinyl)phosphine oxide] and nitrogen combined with phosphorous. Combinations of these reagents with THPC and THPOH were tried as well. The combination of APO and THPC proved to be one of the most effective flame retardants because the properties of the fabric remained good. Unfortunately, APO is expensive and toxic, so it could not be used commercially.

SRRC research results in flame retardant cotton and blends are used by the military in various projects to provide U.S. service men and women with the best protective clothing possible. Some of the materials produced were used by NASA in early space flights and by fire departments throughout the country. The many publications by SRRC scientists kept focus on the dangers of performing risky operations at high temperatures without the use of specialized flame retardant fabrics and undoubtedly resulted in the saving of lives and property.

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Ruth Benerito, Cotton Chemist (1916–2013)

Ruth Benerito is the scientist who led the SRRC team to its developments in durable press cotton. Born in New Orleans in 1916, Benerito is sometimes called the “Queen of Cotton” for her impact on the fiber.

Benerito, who attended the H. Sophie Newcomb Memorial College of Tulane University in New Orleans and earned her Ph.D. in chemistry from the University of Chicago, holds more than 55 patents for her work in cotton chemistry and other projects at the SRRC, including being listed on U.S. Patent #3,432,252, “Method for Producing Resilient Cotton Fabrics through Partial Esterification,” issued in 1969. Benerito was inducted into the National Inventors Hall of Fame in 2008 for her contributions to cotton chemistry.

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Further Reading

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Landmark Designation and Acknowledgments

Landmark Designation

The American Chemical Society designated the evolution of durable press and flame retardant cotton as a National Historic Chemical Landmark in a ceremony at the United States Department of Agriculture ARS Southern Regional Research Center in New Orleans, Louisiana, on May 14, 2004. The plaque commemorating the event reads:

By the 1950s, synthetic fabrics - often wrinkle resistant and flame retardant - began to overtake cotton as the dominant U.S. textile fiber. To reverse this trend chemists and chemical engineers at the Southern Regional Research Center initiated research to modify cotton chemically. Their efforts in developing agents that crosslinked the cellulose fibers and in establishing crosslinking mechanisms led to improved durable press fabrics. SRRC studies also developed new agents that improved the durability of flame retardant cotton to laundering. These significant advances in the properties of cotton enabled this natural fiber to remain a highly competitive textile.

Acknowledgments

Adapted for the internet from “The Evolution of Durable Press and Flame Retardant Cotton,” produced by the National Historic Chemical Landmarks program of the American Chemical Society in 2004.

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Cite this Page

ACS Style

American Chemical Society National Historic Chemical Landmarks. Cotton Products Research. http://www.acs.org/content/acs/en/education/whatischemistry/landmarks/cottonproducts.html (accessed Month Day, Year).

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National Historic Chemical Landmarks plaque and “The Fabric of History” display at the USDA ARS Southern Regional Research Center in New Orleans, Louisiana.
Keith Lindblom/ACS.