Permanent Press: Facts behind the Fabrics

Permanent press clothing and wrinkles. Permanent press – aka crease resistant, crease proof, wrinkle-resistant, durable press, wrinkle free – is another of those 1950s brain storms that seemed like a good idea at the time when we were all infatuated with the promise of science to remove toil and strain from our daily lives. We didn’t need balanced, nutritious meals; we just needed our one-a-day Flintstone Multi-Vitamins. As the 1950s rocketed into the Age of Science, it seemed only right that the Stone Age concept of using a hot chunk of iron to smooth wrinkles from clothes should give way to scientific, easy-care garments. Science took aim at the prime culprit in wrinkling - the weak hydrogen bond which cross-linked the cellulose polymers in cotton.

The cross-linked hydrogen bonds keep in place the cellulose polymers in cellulose fabrics such as cotton, hemp and flax. The bad news is that the hydrogen bonds are relatively weak and easily broken by moisture. Once the hydrogen bonds holding the cellulose fibers in place are broken by moisture, then the fibers can shift place and realign themselves and wrinkles are born in cellulose-based fabrics. The 1950s attempt at good news came from Ruth Benerito, the Mother of Permanent Press, at the Physical Chemistry Research Group of the Cotton Chemical Reactions Laboratory of the USDA Southern Regional Research Center when she developed a process to replace the weak hydrogen bonds with stronger bonds that were water-resistant. The bad news was that the new cross-linking agent was formaldehyde – a toxic chemical that not only smelled bad and made the fabric more brittle but was also carcinogenic and a health hazard.

The bad news of using formaldehyde resins to create permanent cross-linked hydrogen bonds for wrinkle-free clothing continues to this day even though the processes have improved. The early formaldehyde-soaked permanent press garments felt scratchy and stiff and smelled funny. The formaldehyde resins also weakened the fabric. Oh, yes … and formaldehyde has also been recognized as a probable carcinogen that can cause a wide variety of health problems such as burning and watery eyes, respiratory complains such as coughing and difficulty in breathing, and allergic contact dermatitis where permanent press clothing comes into contact with the skin.

Regardless of how we might feel about the ethics of dressing millions and millions of people in clothes reeking with formaldehyde, the accomplishments of Ruth Benerito at the U.S. Department of Agriculture in the 1950s and 60s are impressive. During her many years as a research scientist at the male-dominated USDA, Ruth Benerito garnered 55 patents in creating easy-care cotton fabrics which “saved the cotton industry.”

As the Age of Science Infatuation in the 1950s and early 1960s gave way to the Summer of Love and Age of Rebellion in the 1960s and 1970s and then to the Age of Excess Consumerism in the 1980s and 1990s, process improvements were slowly being made in manufacturing wrinkle-resistant cotton textiles to reduce – but not eliminate – the amount of formaldehyde bound on the surface of the fabric.

How the permanent press processes work. There are two basic processes for finishing cotton textiles with wrinkle-resistant properties: the procure process and the postcure process. The procure process goes like this:

1. The conventional cotton or cotton blend fabric is dyed;
2. Garments are sewn together;
3. Formaldehyde resins are applied to the garments;
4. Garments are tumble dried at a low temperature to remove moisture but not cure the formaldehyde resins and cause cross linking of formaldehyde and hydrogen atoms in the cotton’s cellulose fibers;
5. Press the garments to create creases in the clothing were creases are wanted such as pant legs and sleeves on shirts;
6. Oven cure the pressed garments at a high temperature to cross link the formaldehyde and cellulose fibers to create the permanent press properties.

The postcure process is similar except that the formaldehyde resin is applied in step 2 after the fabric is dyed but before the garments are sewn together and made-up. The postcure process goes like this:

1. Dye cotton or cotton blend fabric;
2. Apply formaldehyde resin;
3. Tumble dry to remove moisture;
4. Sew and garment make-up;
5. Press clothing to create creases where wanted;
6. Oven cure to cross link and create the permanent press properties.

Reducing the amount of formaldehyde in clothing. Two improvements were developed in the 1990’s to reduce the amount of formaldehyde bound into clothing. One method consists of soaking conventional cotton fabric in formaldehyde resins, rolling the toxic fabrics between huge rollers to squeeze out excess formaldehyde resins, and then baking in large ovens at 300° Fahrenheit to cure the formaldehyde resins into the fabrics so that it becomes permanent and doesn’t eventually wash out. Some clothing manufacturers, such as the large multi-national Nisshinbo Industries in Japan, will then also treat the formaldehyde-laced fabric with liquid ammonia to reduce shrinkage.

The other permanent press technology improvement that is actively used today consists of exposing garments to formaldehyde gases which permeate the fabric and then are baked into the clothing. This is known as a vapor phase technology. Manufacturers have their own variations of vapor phase treatment for crease resistance, but the basic technology is composed of fabrics of cotton or other cellulose or regenerated cellulose fibers like bamboo and Tencel / lyocell) or cellulose fabrics blended with synthetics like polyesters, an airtight chamber or room, formaldehyde gas, sulfur dioxide gas, and moisture.

Vapor Phase Technology. The basic process works like this. The clothing or fabric is placed in the airtight chamber and is moistened with water or steam until the water moisture in the fabric is about 5% to 20% of the fabric weight. Formaldehyde gas is pumped into the chamber until the concentration of air in the chamber is approximately 40% to 60% formaldehyde gas and then sulfur dioxide gas is also pumped into the chamber. The sulfur dioxide gas acts as a catalyst causing the formaldehyde gas to cross link and bond with the hydrogen atoms in the cellulose polymers which help create not only crease- and wrinkle-resistance but also help protect from fabric shrinking and improved color retention and color fastness. The amount of formaldehyde that cross-links with the cellulose fibers is 0.3% to 0.6% of the weight of the cellulose fibers. You can see that there is a significant amount of formaldehyde bonded into each garment. Steam seems to be the preferred method of moisturizing the fabric as the steam also forces the formaldehyde gas and sulfur dioxide gas to penetrate the fabric which increases the cross-linking of formaldehyde to the hydrogen atom in the cellulose polymers.

A variation on the vapor phase processing is by impregnating the fabrics with an aqueous solution of a weak acid salt such as zinc chloride, ammonium chloride, sodium di-hydrogen phosphate, magnesium chloride or phosphoric acid after exposure of the fabric to formaldehyde and before garment fabrication to facilitate cross-linking. Manufacturers may vary the chemicals used as a catalyst, the temperature in the gas chamber, whether fabrics are gassed before or after being fabricated into garments, the moisture contents, and other factors but the bottom line is that the finishing of easy-care garments is highly chemical and technology-intensive.

Although Ruth Benerito invented permanent press technology in the labs at the USDA in the 1950’s, it wasn’t until the 1990’s that permanent press popularity really took off. Before then the brittleness, fabric yellowing, and unpleasant feel and smell of permanent press clothes from the heavy formaldehyde discouraged wearers. The new and improved finishing technologies were applied to men’s all-cotton trousers and revitalized the industry. It is more than a little ironic that consumers were drawn to buy 100% cotton slacks because they were perceived as being more natural but they also wanted the easy-care low maintenance clothing even if it was impregnated with toxic and possibly carcinogenic chemicals.

All in the (Formaldehyde) Family. Besides process improvements in the 1990’s, chemical scientists at the large garment manufacturers also began scouting for other chemicals which might reduce or eliminate the amount of formaldehyde baked into wrinkle-free clothing. Clothes labeled permanent-press or durable-press have been dipped in a chemical cornucopia of cross-linking resins such as isocyanates, epoxides, divinylsulfones, aldehydes, chlorohydrins, polycarboxylic acids and N-methylol compounds. Popular with today’s textile chemists are resins of N-methylol compounds which include dimethylol urea, dimethylol ethylene urea, trimethylol trazine, dimethylol methyl carbamate, uron, triazone, and DMDHEU.

The chemical DMDHEU (which you might know better as dimethyol dihydroxy ethylene urea or 1, 2-Dimethylol-4, 5-dihydroxyethyleneurea … ever wonder how they make up these names?) has become the most widely used cross-linking agent. The problem is that DMDHEU, like all the other commonly used cross-linking agents, is still a member of the huge formaldehyde family. The National Toxicology Program at the U.S. Department of Health and Human Services still warn that even though formaldehyde off gassing emissions in clothing have been reduced, DMDHEU has been found “to be causal agents in textile-related dermatitis.” Research is continuing into other possible health hazards from DMDHEU and its other formaldehyde-related cousins.

On a sidebar note: the National Toxicology Program is charged with safeguarding public health by evaluating new chemicals released into the public marketplace. More than 80,000 chemicals are registered for use in the U.S. Each year, manufacturers inject an estimated 2,000 new chemicals into our society through all the countless products that Americans buy each year. Many of these new chemicals have not been adequately tested for potential health hazards.

Wrinkle-resistant fabrics are often treated with softeners such as polyethylene to improve the hand and feel of the perma press fabric and for better wash durability. Some manufacturers are also adding fluorochemical additives to increase stain-resistance.

Another formaldehyde resin currently popular with garment manufacturers is DMUG (dimethylurea glyoxal) because it gives a smoother surface smoothness and greater strength and abrasion resistance than DMDHEU but the crease retention of DMUG is not as good as with DMDHEU so sometimes the two are blended together to create a permanent press cocktail.

Fabric is typically dyed before being treated with formaldehyde resins for crease resistance. Sometimes, sulfur-dyed fabrics impregnated with a formaldehyde resin finish will deteriorate due to the generation of acid from the sulfur dye, especially if black sulfur dye was used. Manufacturers use a slightly modified process to reduce the possibility of acid being generated in people’s washing machines and dryers. But the possibility still exists … it’s just been reduced is all.

The science and technology of chemical fabric finishes is astounding and most people have no idea of the vast range of chemicals – some harsh and toxic – that are used to create those easy care clothes that tempt busy consumers. Today’s easy care clothes are the product of a total textile engineering that includes the selection of the fiber, the yarn characteristics, the fabric construction, preparation, dyeing, finishing formulations, and procedures.

While most conventional textile manufacturers would probably take umbrage at the suggestion that their clothes could qualify as toxic Superfunds, there is no doubt that easy care all-cotton clothing has become highly chemical intensive.

 Chemicals in the laundry room. The chemical war on wrinkles doesn’t end in the hi-tech fabric finishing labs of conventional garment manufacturers but is also waged in ordinary laundry rooms everywhere. Beginning in the early 2000’s, the large laundry care chemical companies launched an assault of wrinkle-attacking laundry products such as Downy Wrinkle Releaser and Wisk detergent with Wrinkle Reducer followed by a platoon of gimmicky wrinkle removing spray-on products such as Faultless Wrinkle Remover spray-on, Apparel Press wrinkle-removing spray, and Wrinkle Out Spray by Stanley Home Products.

The basic premise is that these detergents and sprays will cause clothing wrinkles to melt away and “keep your casual clothes looking neat without all the hassle of ironing.” Besides dissolving wrinkles in that crumpled cotton blouse, these products are also supposed work their magic on wools, silks and dry-clean-only garments. How do they do it? Chemicals … lots of chemicals. Manufacturers do not reveal all the chemicals that are used in their products, only the “active ingredients” so determining exactly what is in what is difficult.

Some of the chemicals commonly used in laundry products to reduce wrinkles include: sodium alcohol ethoxy sulfate, alcohol ethoxylate, sodium linear alkyl benzene sulfonate, propylene glycol, sulphated/sulphonated vegetable oils, zwitterionic surfactants, curable aminosilicones, cellulase enzymes, polyalkyleneoxide modified polydimethylsiloxane, ethoxylated organosilicones, linear aminopolydimethylsiloxane polyalkyleneoxide copolymers, high molecular weight polyacrylamides, betaine siloxane copolymers, alkylactam siloxane copolymers – PLUS tons of artificial fragrances and perfumes to create the chemical illusion of “Morning Fresh”, “Spring Morning”, “Clean Breeze”, “Mountain Spring”, Tropical Clean”, lavender, vanilla, and all the other countless chemical smells that they use to saturate clothes.

Chemicals in the fragrances of consumer products have been identified to the allergens and worse. The Scientific Committee on Cosmetic Products and Non-Food Products (SCCNFP) issued a position paper highlighting the use of allergens in the chemical fragrances often used in consumer detergents. Their position stated “A person sensitised to a certain fragrance material will elicit an allergic response when exposed to this fragrance from any product whether cosmetic or detergents under similar exposure conditions. Thus, it is important that consumers have information on the presence of fragrance chemicals in the respective products.”

Sidebar conversation: For a well done overview of chemicals used in laundry detergents and laundry fragrances, check out the 5-part series in the Bright Hub reporting on the environmental and health impact of conventional and environmentally responsible laundry products. The Bright Hub is a good resource that attempts to "share knowledge about how the simplest scientific idea evolves into tomorrow’s technology.”

Laundry products are often loaded with chemical ingredients that can be unhealthy for people and the environment. A patent application by laundry product giant Unilever on “Wrinkle Reduction Laundry Product Compositions” outlines commonly used chemicals in laundry products such as liquid fabric softeners for reducing wrinkles in cotton and cotton blend fabrics. The Unilever patent application mentions “Additional materials typically used in these formulations include preservatives, pH control agents, viscosity modifying salts, perfumes, optical brighteners, colorants and color care agents.” Unilever is the maker of Wisk with Wrinkle Reducer laundry detergent which spectacularly failed to live up to expectations and marketing hype.

Getting back to how chemists deal with wrinkles, laundry room wrinkle removers reduce wrinkles by “relaxing” the fibers which actually means that wrinkle-relaxing products penetrate fabrics and apply a find coat of lubricate to the fiber surfaces so that the fibers can slide more easily relative to each other and can be pulled straight, resulting in less wrinkles. The ingredients used to coat fabric fibers so that wrinkles can be smoothed out are usually a polyolefine type softener such as polyethylene and polypropylene or a curable amine functional silicone.

Many consumers have reported after using some of these wrinkle-relaxer and fabric softening products that their clothes felt like they have a film on them that builds with continued use. Consumer tests have also questioned the effectiveness at eliminating or reducing wrinkles. Don’t expect these products to allow you to toss out that rusty old steam iron.

The future of wrinkle-reducing textile manufacturing and laundry products: Don’t expect the unnatural laundry products industry to rollover and give up. The laundry care market is an $11+ billion industry and growing at a rate of more than 5% annually. The big names are spending big bucks to develop and roll out new chemical additives and new technologies to improve the garment and textile markets. Proctor & Gamble spent over $100 million just to build a new fabric and home care research and development center. Proctor & Gamble also developed a new cellulosic Liquifiber technology which is used in Tide Ultra powder under the trademark WearCare. Liquid Detergents - Second Edition, edited by Kou-Yann Lai from CRC Press describes the Liquifiber technology as hydrophobically modified cellulosic polymers that binds to cotton fibers and effectively glues the cotton fibril in place so that they do not break lose causing fraying, microscopic pills, color degradation, and wrinkling. Curiously, the basic concept is the same as that used in Proctor & Gamble’s Pantene Pro-V Restoratives Time Renewal shampoo and conditioner collection for hair. I guess that fiber is fiber in the R & D labs.

The use of enzymes in all phases of textile manufacturing and especially garment finishing will continue to grow. Expect enzyme use in detergents and laundry products to also grow. GMO (genetically modified organisms) technology is also becoming more prevalent as new enzyme cocktails are being developed for use in the textile and home laundry product industries. Genencor is one of the largest of the biotechnology companies providing textile enzymes for textile manufacturing and finishing.

Look also for growth in nano-technologies for textiles. Nanotech textiles have quietly been infiltrating the textile manufacturing industry with new fabrics which are touted as having anti-wrinkle, anti-static, anti-stain, and anti-bacterial. Because nano-textiles have the potential to be a high tech tsunami on the textile industry we will explore the potential impacts in the next post.Stay tuned...

Enjoy.

Michael