Textile chemicals – beginning with the one used the most

16 01 2013

saltLet’s begin our review of chemicals used in textile processing with the one chemical that is used most often and in far greater quantity than any other: salt. That’s right. Common table salt, the kind you probably use every day. But in the quantities used by this industry it becomes a monster – we’ll get to that in a minute.

Salt is used in the dye process. The way the dyestuff bonds to the fibers is very important – and the most permanent, colorfast dyes are the ones that are most tightly attached to the fiber molecules (called reactive dyes). Here’s how salt comes into the picture:

When fabrics made of cellulosic (i.e., cotton, linen, hemp or viscose) are dyed, they’re immersed in water which contains dyes which have been dissolved in the water. The surface of the fabric gets covered in negative ionic charges. The reactive dyes used most often to dye cellulosic fabrics also develop a negative charge, so the fibers actually repel the dye – like two magnets repelling each other. If we try to dye a cellulosic fabric without using salt, the dye molecules just roll off the surface of the fibers and the fabric does not show much color change. So these reactive dyes need the addition of salt to “push” the dyes out of solution and into the cloth by neutralizing the negative charge.

The salt acts like a glue to hold the dye molecules in place, and with the addition of alkali, a certain percentage of the dyestuff (called the “fixation rate”) will permanently grab hold of the fiber and become a part of the fiber molecule rather than remaining as an independent chemical entity. For conventional reactive dyes, the fixation rate is often less than 80%, resulting in waste of dyestuff, and also the need to remove that 20% (which is not fixed) from the fabric.(1) But this is incredibly difficult when the “unreacted” dyes are still “glued” onto the fabric by salt. So vast amounts of water are required to simply dilute the salt concentrations to a point where it no longer acts as glue.

That means the textile effluent contains both dyestuff and salt (lots of salt!) The concentrations of salt in the dye bath can be as high as 100 gm per liter. In the worst cases, equal weights of salt to fabric is used to apply reactive dye (i.e., if dyeing 10 lbs of fabric, you need 10 lbs of salt). Think of the billions of yards of fabric that’s produced each year: In Europe alone, 1 million tons of salt is discharged into waterways each year.(2) In areas where salt is discharged into the ecosystem, it takes a long, long time for affected areas to recover, especially in areas of sparse rainfall – such as Tirupur, India.

Tirupur is one of the world’s centers for clothing production , home of 765 dyeing and bleaching industries. These dyehouses had been dumping untreated effluent into the Noyyal River for years, rendering the water unsuitable or irrigation – or drinking. In 2005, the government shut down 571 dyehouses because of the effluent being discharged into the Noyyal. The mill owners said they simply couldn’t afford to put pollution measures into place. The industry is too important to India to keep the mills closed for long, so the government banned the discharge of salt and asked for an advance from the mills before allowing them to re-open. But … on February 4, 2011, the Madras high court ordered 700 dye plants to be shut down because of the damage the effluent was doing to the local environment. Sigh. (Read more about Tirupur here.)

Unfortunately, the salt in textile effluent is not made harmless by treatment plants and can pass straight through to our rivers even if it has been treated. The salt expelled into waterways (untreated) coupled with salt from roadway de-icing has led to the increase in salt in our waters in the United States – salt levels in Lake George have nearly tripled since 1980,(3) which mirrors many other parts of the U.S. Highest levels occur during the annual ice-out and snowmelt where high salt concentrations in streams flowing into Lake George have been linked to die offs of fish, and is known as “spring shock”. A study in Toronto found that half the wells tested exceeded the limit of 20mg of salt per liter of water, 20% exceeded 100mg/liter and 6% exceeded 250mg/liter. (4) It becomes a public health concern for people who drink this water, because it can exacerbate high blood pressure and hypertension in humans. This increase in our drinking water can also cause problems with water balance in the human body. Salt in water is also responsible for the release of mercury into the water system.

Recycling the salt used during the dye process is possible, and this has been used by many of the dyers in Tirupur, and elsewhere, who operate zero discharge facilities. The effluent is cleaned and then the salt is recovered using an energy intensive process to evaporate the water and leave the solid, re-useable salt. This sounds like a good idea – it reduces the pollution levels – but the carbon footprint goes through the roof, so salt recovery isn’t necessarily the best option. In fact, in some areas of the world where water is plentiful and the salt can be diluted in the rivers adequately, it may be better to simply discharge salt than to recover it.

There are some new “low salt” dyes that require only half the amount of “glue”: Ciba Specialty Chemicals, a Swiss manufacturer of textile dyes (now part of BASF) produces a dyestuff which requires less salt. As the company brochure puts it: “Textile companies using the new dyes are able to reduce their costs for salt by up to 2 percent of revenues, a significant drop in an industry with razor-thin profit margins” but these dyes are not widely used because they’re expensive – and manufacturers are following our lead in demanding ever cheaper costs. There are also new low-liquor-ratio (LLR) jet dyeing machines – but that doesn’t mean zero salt, so there is still salt infused effluent which must be treated. And these new ultra low liquor ratio machines are very expensive.

The best option is to avoid salt altogether. Though the salt itself is not expensive, using less salt delivers substantial benefits to the mill because the fabric requires less rinsing in hot water (and hence reductions in energy and water) as well as cost savings of up to 10% of the total process costs.(5) So what about using no salt at all?

There are two ways to dye fabrics without salt: “continuous dyeing” and “cold pad batch dyeing”. Continuous dyeing means that the dye is applied with alkali to activate the dye fixation; the fabric is then steamed for a few minutes to completely fix the dyestuff. Cold pad batch dyeing applies the dyestuff with alkali and the fabric is simply left at room temperature for 24 hours to fix the dye.

Both of these methods don’t use salt, so the unfixed dye chemicals are easier to remove because there is no salt acting as the “glue” – and therefore less water is used. An additional benefit is having a lower salt content in the effluent. So why don’t companies use this method? Continuous dyeing requires investment in big, expensive machines that only make environmental sense if they can be filled with large orders – because they use lots of energy even during downtime.

Cold pad batch machines are relatively inexpensive to buy and run, they are highly productive and can be used for a wide range of fabrics. Yet only 3% of knitted cotton fabric is dyed in Asia using cold pad batch machines.
Why on earth don’t these mills use cold pad batch dyeing? I would love to hear from any mill owners who might let us know more about the economics of dyeing operations.

(1) http://lifestylemonitor.cottoninc.com/Supply-Chain-Insights/Sustainable-Dyeing-Solutions-02-10/
(2) Dyeing for a change: Current Conventions and New Futures in the Textile Color Industry (2006, July) http://www.betterthinking.co.uk
(3) http://www.fundforlakegeorge.org/assets/pdf_files/Fact%20Sheet%2011%20Salt.pdf
(4) http://www.digitaltermpapers.com/a2206.htm
(5) “A Practical Guide For Responsible Sourcing”, The National Resources Defense Council (NRDC), February 2010.





What does “mercerized” cotton mean?

5 12 2012

fullsizeMercerization is a process applied to cellulosic  fibers  – typically cotton (or cotton-covered thread with a polyester core)  but hemp and linen can be mercerized also – to increase luster.  It is done after weaving (in the case of fabrics) or spinning (for yarns or threads).  But early on it was found that the process also had secondary benefits:  the mercerized fibers were able to absorb more water, and therefore absorb more dye, making the color of the dyed cloth brighter and deeper.  The difference is dramatic:  mercerization increases the absorption of dyestuffs by as much as 25%.[1]  unmercerized-101mercerized-101Not only is the color brighter, it also gives the cloth a better resistance to multiple washings,  keeping the colors bright and unchanged over time.   In addition to increasing luster and affinity to dyestuffs, the  treatment increases strength, smoothness, resistance to mildew, and also reduces lint.  So higher quality yarns and fabrics,  for example, are always mercerized.

The process goes back to the 1880’s.   John Mercer was granted a British Patent for his discovery that cotton and other fibers changed character when subjected to caustic soda (NaOh, also known as sodium hydroxide or lye), sulfuric acid, and/or other chemicals.   One of the changes was that caustic soda caused the fiber to swell, become round and straighten out.  But so what – these changes didn’t impart any luster to the fibers, so his patent was largely ignored.  Then in 1890 Horace Lowe found that by applying Mercer’s caustic soda process to cotton yarn or fabric under tension, the fabric gained a  high luster  as a result of the light reflection off the smooth, round surface created by the NaOH. It became an overnight success and revolutionized the cotton industry. The rest is history.[2]

Later testing proved that cotton fiber in its roving state (no twist in the yarns) would absorb more NaOH than fiber in a twisted state and as a result would absorb more water or dye.  Since fine, long stapled fiber gives the best absorption with the lowest twist, ( some twist is required for treating under tension to gain luster) it is usually the long fiber types of cotton (Sea Island, Egyptian, Pima) that are selected for yarn to be mercerized.   So mercerized cotton fabric starts with a better quality cotton fiber.

How is it done?

To get the desired luster and tensile strength,  cotton is held under specified tension for about ten minutes with an application of between 21%-23% caustic soda (NaOH) and wetting agents (used to facilitate the transfer of the NaOH into the fibers), at room temperature.  Then the fabric is neutralized in an acid bath.

Luster is a result of light reflection off a surface. The more glass like the surface, the better the luster. Yarn in its spun, treated state still has a very fine covering of tiny fiber ends (fuzz). This fuzz is removed by passing the yarn (or fabric) through a controlled heated atmosphere termed singeing (gas fired in the past, electric more currently) resulting in a cleaner surface.  (Luster is a result of light reflection off a surface. The more glass like the surface, the better the luster.)
You knew I’d have to look at the toxicity profile of sodium hydroxide, which is considered one of the building blocks of chemistry.  It’s a very powerful alkali.   It’s used in industry in a broad range of categories: chemical manufacturing; pulp and paper manufacturing; cleaning products such as drains, pipe lines and oven cleaners ; petroleum and natural gas; cellulose film;  and water treatment as well as textiles. The US Food and Drug Administration (FDA) considers sodium hydroxide to be generally safe, and recognizes it as not being found to pose unacceptable dietary risks, though it is generally only used on food contact surfaces rather than in foodstuffs.

The chemical is toxic to wildlife, and the EPA requires that effluent containing NaOH not be discharged into groundwater.  Because sodium hydroxide falls in the group of chemicals (salts) which are by far the most often used in textile processing, the sheer volume of NaOH used by the textile industry is important to recognize.  Usual salt concentrations in cotton mill wastewater can be 2,000 – 3,000 ppm[3], far in excess of Federal guidelines for in-stream salt concentrations of 230 ppm.  So treatment of effluent is very important, as prevention is the only reasonable alternative to solve the environmental problems associated with this hard-to-treat, high volume waste.  I have read that electrochemical cell treatment might be a substitute for using NaOH to mercerize.  This process occurs in a low voltage electrochemical cell that mercerizes, sours, and optionally bleaches without effluents and without the purchase of bulk caustic, neutralizing acids, or bleaches.





How to buy a quality sofa – part 4: natural fibers

10 10 2012

Since the 1960s, the use of synthetic fibers has increased dramatically,  causing the natural fiber industry to lose much of its market share. In December 2006, the United Nations General Assembly declared 2009 the International Year of Natural Fibres (IYNF); a year-long initiative focused on raising global awareness about natural fibers with specific focus on increasing market demand to help ensure the long-term sustainability for farmers who rely heavily on their production.

                       International Forum for Cotton Promotion

Natural fibers  have a history of being considered the fibers that are easiest to live with, valued for their comfort, soft hand and versatility.  They also carry a certain cachet:  cashmere, silk taffeta and 100% pure Sea Island cotton convey different images than does 100% rayon,  pure polyester or even Ultrasuede, don’t they?  And natural fibers, being a bit of an artisan product, are highly prized especially in light of campaigns by various trade associations to brand fiber:    “the fabric of our lives” from Cotton, Inc. and merino wool with the pure wool label are two examples.                                                              

Preferences for natural fibers seem to be correlated with income; in one study, people with higher incomes preferred natural fibers by a greater percentage than did those in lower income brackets.   Cotton Incorporated funded a study that demonstrated that  66% of all women with household incomes over $75,000 prefer natural fibers to synthetic.

What are the reasons, according to the United Nations, that make natural fibers so important?  The UN website, Discover Natural Fibers lists the following reasons why natural fibers are a good choice.  Please remember that this list does not include organic natural fibers, which provide even more benefits (but that’s another post):

  1. Natural fibers are a healthy choice.
    1. Natural fiber textiles absorb perspiration and release it into the air, a process called “wicking” that creates natural ventilation. Because of their more compact molecular structure, synthetic fibers cannot capture air and “breathe” in the same way. That is why a cotton T-shirt is so comfortable to wear on a hot summer’s day, and why polyester and acrylic garments feel hot and clammy under the same conditions. (It also explains why sweat-suits used for weight reduction are made from 100% synthetic material.) The bends, or crimp, in wool fibers trap pockets of air which act as insulators against both cold and heat – Bedouins wear thin wool to keep them cool. Since wool can absorb liquids up to 35% of its own weight, woollen blankets efficiently absorb and disperse the cup of water lost through perspiration during sleep, leaving sheets dry and guaranteeing a much sounder slumber than synthetic blankets.
    2. The “breathability” of natural fiber textiles makes their wearers less prone to skin rashes, itching and allergies often caused by synthetics. Garments, sheets and pillowcases of organic cotton or silk are the best choice for children with sensitive skins or allergies, while hemp fabric has both a high rate of moisture dispersion and natural anti-bacterial properties.   Studies by Poland’s Institute of Natural Fibers have shown that 100% knitted linen is the most hygienic textile for bed sheets – in clinical tests, bedridden aged or ill patients did not develop bedsores. The institute is developing underwear knitted from flax which, it says, is significantly more hygienic than nylon and polyester. Chinese scientists also recommend hemp fiber for household textiles, saying it has a high capacity for absorption of toxic gases.
  2. Natural fibers are a responsible choice.
    1. Natural fibers production, processing and export are vital to the economies of many developing countries and the livelihoods of millions of small-scale farmers and low-wage workers. Today, many of those economies and livelihoods are under threat: the global financial crisis has reduced demand for natural fibers as processors, manufacturers and consumers suspend purchasing decisions or look to cheaper synthetic alternatives.
    2. Almost all natural fibers are produced by agriculture, and the major part is harvested in the developing world.
      1. For example, more than 60% of the world’s cotton is grown in China, India and Pakistan. In Asia, cotton is cultivated mainly by small farmers and the sale of cotton provides the primary source of income for some 100 million rural households.
      2. In India and Bangladesh, an estimated 4 million marginal farmers earn their living – and support 20 million dependents – from the cultivation of jute, used in sacks, carpets, rugs and curtains. Competition from synthetic fibers has eroded demand for jute over recent decades and, in the wake of recession, reduced orders from Europe and the Middle East could cut jute exports even further.
      3. Silk is another important industry in Asia. Raising silkworms generates income for some 700 000 farm households in India, while silk processing provide jobs for 20 000 weaving families in Thailand and about 1 million textile workers in China.
      4. Each year, developing countries produce around 500 000 tonnes of coconut fiber – or coir – mainly for export to developed countries for use in rope, nets, brushes, doormats, mattresses and insulation panels. In Sri Lanka, the single largest supplier of brown coir fiber to the world market, coir goods account for 6% of agricultural exports, while 500 000 people are employed in small-scale coir factories in southern India.
      5. Across the globe in Tanzania, government and private industry have been working to revive once-booming demand for sisal fiber, extracted from the sisal agave and used in twine, paper, bricks and reinforced plastic panels in automobiles. Sisal cultivation and processing in Tanzania directly employs 120 000 people and the sisal industry benefits an estimated 2.1 million people.
  3. Natural fibers are a sustainable choice.
    1. Natural fibers will play a key role in the emerging “green” economy based on energy efficiency, the use of renewable feed stocks in bio-based polymer products, industrial processes that reduce carbon emissions and recyclable materials that minimize waste.  Natural fibers are a renewable resource, par excellence – they have been renewed by nature and human ingenuity for millennia. During processing, they generate mainly organic wastes and leave residues that can be used to generate electricity or make ecological housing material. And, at the end of their life cycle, they are 100% biodegradable.
    2. An FAO study estimated that production of one ton of jute fiber requires just 10% of the energy used for the production of one ton of synthetic fibers (since jute is cultivated mainly by small-scale farmers in traditional farming systems, the main energy input is human labor, not fossil fuels).
    3. Processing of some natural fibers can lead to high levels of water pollutants, but they consist mostly of biodegradable compounds, in contrast to the persistent chemicals, including heavy metals, released in the effluent from synthetic fiber processing. More recent studies have shown that producing one ton of polypropylene – widely used in packaging, containers and cordage – emits into the atmosphere more than 3 ton of carbon dioxide, the main greenhouse gas responsible for global warming. In contrast, jute absorbs as much as 2.4 tonnes of carbon per tonne of dry fiber.
    4. The environmental benefits of natural fiber products accrue well beyond the production phase. For example, fibers such as hemp, flax and sisal are being used increasingly as reinforcing in place of glass fibers in thermoplastic panels in automobiles. Since the fibers are lighter in weight, they reduce fuel consumption and with it carbon dioxide emissions and air pollution.
    5. But where natural fibers really excel is in the disposal stage of their life cycle. Since they absorb water, natural fibers decay through the action of fungi and bacteria – this releases the fixed CO2 in the fibers and closes the cycle; it also improves soil structure.  Synthetics present society with a range of disposal problems. In land fills they release heavy metals and other additives into soil and groundwater. Recycling requires costly separation, while incineration produces pollutants and, in the case of high-density polyethylene, 3 tonnes of carbon dioxide emissions for every tonne of material burnt. Left in the environment, synthetic fibers contribute, for example, to the estimated 640 000 tonnes of abandoned fishing nets and gear in the world’s oceans.
  4. Natural fibers are a high-tech choice.
    1. Natural fibers have intrinsic properties – mechanical strength, low weight and low cost – that have made them particularly attractive to the automobile industry.
      1. In Europe, car makers are using mats made from abaca, flax and hemp in press-molded      thermoplastic panels for door liners, parcel shelves, seat backs, engine shields and headrests.
        1. For consumers, natural fiber composites in automobiles provide better thermal and acoustic insulation than fiberglass, and reduce irritation of the skin and respiratory system. The low density of plant fibers also reduces vehicle weight, which cuts fuel consumption.
        2. For car manufacturers, the moulding process consumes less energy than that of fibreglass and produces less wear and tear on machinery, cutting production costs by up to 30%. The use of natural fibres by Europe’s car industry is projected to reach 100 000 tonnes by 2010. German companies lead the way. Daimler-Chrysler has developed a flax-reinforced polyester composite, and in 2005 produced an award-winning spare wheel well cover that incorporated abaca yarn from the Philippines. Vehicles in some BMW series contain up to 24 kg of flax and sisal. Released in July 2008, the Lotus Eco Elise (pictured above) features body panels made with hemp, along with sisal carpets and seats upholstered with hemp fabric. Japan’s carmakers, too, are “going green”. In Indonesia, Toyota manufactures door trims made from kenaf and polypropylene, and Mazda is using a bioplastic made with kenaf for car interiors.
    1. Worldwide, the construction industry is moving to natural fibres for a range of products, including light structural walls, insulation materials, floor and wall coverings, and roofing. Among recent innovations are cement blocks reinforced with sisal fibre, now being manufactured in Tanzania and Brazil. In India, a growing shortage of timber for the construction industry has spurred development of composite board made from jute veneer and coir ply – studies show that coir’s high lignin content makes it both stronger and more resistant to rotting than teak. In Europe, hemp hurd and fibres are being used in cement and to make particle boards half the weight of wood-based boards. Geotextiles are another promising new outlet for natural fibre producers. Originally developed in the Netherlands for the construction of dykes, geotextile nets made from hard natural fibres strengthen earthworks and encourage the growth of plants and trees, which provide further reinforcement. Unlike plastic textiles used for the same purpose, natural fibre nets – particularly those made from coir – decay over time as the earthworks stabilize.
  1. Natural fibers are a fashionable choice.
    John Patrick Organic Fall/Winter 2010
    1. Natural fibers are at the heart of a fashion movement that goes by various names: sustainable, green, uncycled, ethical, eco-, even eco-environmental. It focuses fashion on concern for the environment, the well-being of fiber producers and consumers, and the conditions of workers in the textile industry. Young designers now offer “100% carbon neutral” collections that strive for sustainability at every stage of their garments’ life cycle – from production, processing and packaging to transportation, retailing and ultimate disposal. Preferred raw materials include age-old fibres such as flax and hemp, which can be grown without agrochemicals and produce garments that are durable, recyclable and biodegradable. Fashion collections also feature organic wool, produced by sheep that have not been exposed to pesticide dips, and “cruelty-free” wild silk, which is harvested – unlike most silk – after the moths have left their cocoons.
    2. The Global Organic Textile Standard (GOTS)   sets strict standards on chemicals permitted in processing, on waste water treatment, packaging material and technical quality parameters, on factory working conditions and on residue testing.
    3. Sustainable fashion intersects with the “fair trade” movement, which offers producers in developing countries higher prices for their natural fibres and promotes social and environmental standards in fibre processing. Fair trade fashion pioneers are working with organic cotton producers’ cooperatives in Mali, hand-weavers groups in Bangladesh and Nepal, and alpaca producers in Peru. A major UK chain store launched in 2007 a fair trade range of clothing that uses cotton “ethically sourced” from farmers in the Gujarat region of India. It has since sold almost 5 million garments and doubled sales in the first six months of 2008.
    4. Another dimension of sustainable fashion is concern for the working conditions of employees in textile and garment factories, which are often associated with long working hours, exposure to hazardous chemicals used in bleaching and dyeing, and the scourge of child labor. The  Global Organic Textile Standard (GOTS), widely accepted by manufacturers, retailers and brand dealers, includes a series of “minimum social criteria” for textile processing, including a prohibition on the use of child labor, workers’ freedom of association and right to collective bargaining, safe and hygienic working conditions, and “living wages”.




How to buy a quality sofa – part 4: synthetic fibers

3 10 2012

So from last week’s post, you  know that you want a durable, colorfast fabric that will be lovely to look at and wonderful to live with.  What’s the best choice?  I’m so glad you asked.

You have basically two choices in fibers:  natural (cotton, linen, wool, hemp, silk)  or synthetic (polyester, acrylic, nylon, etc.).  Many fabrics today are made from blends of natural and synthetic fibers – it has been said that most sheet sets sold in the U.S. are cotton/poly blends.

Natural fibres breathe, wicking moisture from the skin, providing even warmth and body temperature;  they are renewable, and decay at end of life.  On the other hand, synthetics do not breathe,  trapping body heat and perspiration; they are based on crude oil, definitely a non-renewable resource and they do not decompose at end of life, but rather remain in our landfills, leaching their toxic monomers into our groundwater.  They are, however, cheap and durable.

I like to think that even without the health issues involved I’d choose to live with natural fibers, since they work so well with humans!  The fibers themselves present no health issues and they’re comfortable.  But they simply don’t last as long as synthetics. But I have begun to see the durability of synthetics as their Dorian Grey aspect, in other words they last so long that they’ve become a huge problem.  By not decomposing, they just break into smaller and smaller particles which leach their toxic monomers into our groundwater.

The impact on health (ours the the planet’s) is an issue that’s often overlooked when discussing the merits of natural vs. synthetic.   And it’s a complex issue, so this week we’ll explore synthetic fibers, and next week we’ll look at natural fibers.

The most popular synthetic fiber in use today is polyester.

At this point, I think it would be good to have a basic primer on polyester production, and I’ve unabashedly lifted a great discussion from Marc Pehkonen and Lori Taylor, writing in their website diaperpin.com:

Basic polymer chemistry isn’t too complicated, but for most people the manufacture of the plastics that surround us is a mystery, which no doubt suits the chemical producers very well. A working knowledge of the principles involved here will make us more informed users.

Polyester is only one compound in a class of petroleum-derived substances known as polymers. Thus, polyester (in common with most polymers) begins its life in our time as crude oil. Crude oil is a cocktail of components that can be separated by industrial distillation. Gasoline is one of these components, and the precursors of polymers such as polyethylene are also present.

Polymers are made by chemically reacting a lot of little molecules together to make one long molecule, like a string of beads. The little molecules are called monomers and the long molecules are called polymers.

Like this:

O + O + O + . . . makes OOOOOOOOOOOOOOOO

Depending on which polymer is required, different monomers are chosen. Ethylene, the monomer for polyethylene, is obtained directly from the distillation of crude oil; other monomers have to be synthesized from more complex petroleum derivatives, and the path to these monomers can be several steps long. The path for polyester, which is made by reacting ethylene glycol and terephthalic acid, is shown below. Key properties of the intermediate materials are also shown.

The polymers themselves are theoretically quite unreactive and therefore not particularly harmful, but this is most certainly not true of the monomers. Chemical companies usually make a big deal of how stable and unreactive the polymers are, but that’s not what we should be interested in. We need to ask, what about the monomers? How unreactive are they?

We need to ask these questions because a small proportion of the monomer will never be converted into polymer. It just gets trapped in between the polymer chains, like peas in spaghetti. Over time this unreacted monomer can escape, either by off-gassing into the atmosphere if the initial monomers were volatile, or by dissolving into water if the monomers were soluble. Because these monomers are so toxic, it takes very small quantities to be harmful to humans, so it is important to know about the monomers before you put the polymers next to your skin or in your home. Since your skin is usually moist, any water-borne monomers will find an easy route into your body.

Polyester is the terminal product in a chain of very reactive and toxic precursors. Most are carcinogens; all are poisonous. And even if none of these chemicals remain entrapped in the final polyester structure (which they most likely do), the manufacturing process requires workers and our environment to be exposed to some or all of the chemicals shown in the flowchart above. There is no doubt that the manufacture of polyester is an environmental and public health burden that we would be better off without.

What does all of that mean in terms of our health?  Just by looking at one type of cancer, we can see how our lives are being changed by plastic use:

  • The connection between plastic and breast cancer was first discovered in 1987 at Tufts Medical School in Boston by research scientists Dr. Ana Soto and Dr. Carlos Sonnenschein. In the midst of their experiments on cancer cell growth, endocrine-disrupting chemicals leached from plastic test tubes into the researcher’s laboratory experiment, causing a rampant proliferation of breast cancer cells. Their findings were published in Environmental Health Perspectives (1991)[1].
  • Spanish researchers, Fatima and Nicolas Olea, tested metal food cans that were lined with plastic. The cans were also found to be leaching hormone disrupting chemicals in 50% of the cans tested. The levels of contamination were twenty-seven times more than the amount a Stanford team reported was enough to make breast cancer cells proliferate. Reportedly, 85% of the food cans in the United States are lined with plastic. The Oleas reported their findings in Environmental Health Perspectives (1995).[2]
  • Commentary published in Environmental Health Perspectives in April 2010 suggested that PET might yield endocrine disruptors under conditions of common use and recommended research on this topic. [3]

These studies support claims that plastics are simply not good for us – prior to 1940, breast cancer was relatively rare; today it affects 1 in 11 women.  We’re not saying that plastics alone are responsible for this increase, but to think that they don’t contribute to it is, we think, willful denial.  After all, gravity existed before Newton’s father planted the apple tree and the world was just as round before Columbus was born.

Polyester fabric is soft, smooth, supple – yet still a plastic.  It contributes to our body burden in ways that we are just beginning to understand.  And because polyester is highly flammable, it is often treated with a flame retardant, increasing the toxic load.  So if you think that you’ve lived this long being exposed to these chemicals and haven’t had a problem, remember that the human body can only withstand so much toxic load – and that the endocrine disrupting chemicals which don’t seem to bother you may be affecting generations to come.

And then there is acrylic.  The key ingredient of acrylic fiber is acrylonitrile, (also called vinyl cyanide). It is a carcinogen (brain, lung and bowel cancers) and a mutagen, targeting the central nervous system.  According to the Centers for Disease Control and Prevention, acrylonitrile enters our bodies through skin absorption, as well as inhalation and ingestion.  So could the acrylic fibers in our acrylic fabrics be a contributing factor to these results?

Acrylic fibers are just not terrific to live with anyway.  Acrylic manufacturing involves highly toxic substances which require careful storage, handling, and disposal. The polymerization process can result in an explosion if not monitored properly. It also produces toxic fumes. Recent legislation requires that the polymerization process be carried out in a closed environment and that the fumes be cleaned, captured, or otherwise neutralized before discharge to the atmosphere.(4)

Acrylic is not easily recycled nor is it readily biodegradable. Some acrylic plastics are highly flammable and must be protected from sources of combustion.

Just in case you missed the recent report which was published in Occupational and Environmental Medicine [5], a Canadian study found that women who work with some common synthetic materials could treble their risk of developing breast cancer after menopause. The data included women working in textile factories which produce acrylic fabrics – those women have seven times the risk of developing breast cancer than the normal population, while those working with nylon fibers had double the risk.

What about nylon?  Well, in a nutshell, the production of nylon includes the precursors benzene (a known human carcinogen) and hydrogen cyanide gas (extremely poisonous); the manufacturing process releases VOCs, nitrogen oxides and ammonia.  And finally there is the addition of those organophosphate flame retardants and dyes.

[1] http://www.bu-eh.org/uploads/Main/Soto%20EDs%20as%20Carcinogens.pdf

[2] http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info:doi/10.1289/ehp.95103608

[3] Sax, Leonard, “Polyethylene Terephthalate may Yield Endocrine Disruptors”,
Environmental Health Perspectives, April 2010, 118 (4): 445-448

(4) ) http://www.madehow.com/Volume-2/Acrylic-Plastic.html

(5) Occupational and Environmental Medicine 2010, 67:263-269 doi: 10.1136/oem.2009.049817 (abstract: http://oem.bmj.com/content/67/4/263.abstract) SEE ALSO: http://www.breastcancer.org/risk/new_research/20100401b.jsp AND http://www.medpagetoday.com/Oncology/BreastCancer/19321





How to buy a “quality” sofa – part 4, fabric

26 09 2012

This week we’ll begin to talk about the fabric used in your sofa – which we (of course) think is a very complicated and important topic! One thing to remember is that there is much more fabric used in constructing an upholstered piece of furniture than just the decorative fabric that you see covering the piece – a typical “quality” sofa also uses about 20 yards of decorative fabric, plus 20 yds of lining fabric, 15 yds of burlap and 10 yds of muslin, for a total of 65 yards of fabric!

So what do people look for in an upholstery fabric?

After color, fabric durability is probably top of everybody’s list.  Durability translates into most people’s minds as “heft” – in other words, a lightweight cotton doesn’t usually come to mind. But more important in evaluating durability than the weight of the fabric is the length of the fibers.  Cotton as a fiber is much softer and of shorter lengths than either hemp or linen, averaging 0.79 -1.30 inches in length.  Hemp’s average length is 8 inches, but can range up to 180 inches in length. In a study done by Tallant et. al. of the Southern Regional Research Laboratory,  “results indicate that increases in shortfibers are detrimental to virtually all yarn and fabric properties and require increased roving twist for efficient drafting during spinning. A 1% increase in fibers shorter than 3/8 in. causes a strength loss in yarns of somewhat more than 1%.”[1]    In fact, the US textile industry has  advocated obtaining the Short Fiber Content (SFC) for cotton classification.  SFC is defined as the percentage of fibers shorter than ½ inch.  So a lower cost sofa upholstered in cotton fabric, even one identified as an upholstery fabric, could have been woven of short fiber cotton, a cheaper alternative to longer fiber cotton and one which is inherently less durable.

Patagonia, the California manufacturer of outdoor apparel, has conducted  tests on both hemp and other natural fibers, with the results showing that hemp has eight times the tensile strength and four times the durability of other natural fibers.   Ecolution had a hemp twill fabric tested for tensile and tear strength, and compared the results with a 12-oz cotton denim.  Hemp beat cotton every time:   Overall, the 100% hemp fabric had 62% greater tear strength and 102% greater tensile strength. [2]   And polyester trumps them both – but that’s a whole different ballgame, and we’ll get to that eventually.

There is a high correlation between fiber strength and yarn strength.  People have used silk as an upholstery fabric for hundreds of years, and often the silk fabric is quite lightweight;  but silk is a very strong fiber.

In addition to the fiber used, yarns are given a twist to add strength. This is called Twist Per Inch or Meter (TPI or TPM) – a tighter twist (or more turns per inch) generally gives more strength.  These yarns are generally smooth and dense.

So that brings us to weave structure.  Weave structures get very complicated, and we can refer you to lots of references for those so inclined  to do more research (see references listed at the end of the post).

But knowing the fibers, yarn and weave construction still doesn’t answer people’s questions – they want some kind of objective measurement.  So in order to objectively compare fabrics,  tests to determine wear were developed (called abrasion tests), and many people today refer to these test results as a way to measure fabric durability.

Abrasion test results are supposed to forecast how well a fabric will stand up to wear and tear in upholstery applications.  There are two tests generally used:  Martindale  and Wyzenbeek (WZ).  Martindale is the preferred test in Europe; Wyzenbeek is preferred in the United States.  There is no correlation between the two tests, so it’s not possible to estimate the number of cycles that would be achieved on one test if the other were known:

  • Wyzenbeek (ASTM D4157-02):  a piece of cotton duck  fabric or wire mesh is rubbed in a straight back and forth motion on a      piece of fabric until “noticeable wear” or thread break is evident.  One back and forth motion is called a “double rub” (sometimes written as “dbl rub”).
  • Martindale (ASTM D4966-98):  the abradant in this test is worsted wool or wire screen, the fabric specimen is a circle or round      shape, and the rubbing is done in a figure 8, and not in a straight line as in Wyzenbeek.  One circle 8 is a cycle.

The Association for Contract Textiles performance guidelines lists the following test results as being suitable for commercial fabrics:

Wyzenbeek Martindale
General contract 15,000 20,000
Heavy duty contract 30,000 40,000

According to the Association for Contract Textiles, end use examples of “heavy duty contract” where 30,000 WZ results should be appropriate are single shift corporate offices, hotel rooms, conference rooms and dining areas.  Areas which would require higher than 30,000 WZ are: 24 hour facilities (like transportation terminals, healthcare emergency rooms, casino gambling areas,  and telemarketing offices) and theatres, stadiums, lecture halls and fast food restaurants.

Sina Pearson, the textile designer, has been quoted in the Philadelphia Inquirer as saying that 6,000 rubs (Wyzenbeek) may be “just fine” for residential use”[3]   The web site for Vivavi furniture gives these ratings for residential use:

Wyzenbeek
from to
Light use 6,000 9,000
Medium use 9,000 15,000
Heavy use 15,000 30,000
Maximum use >30,000

Theoretically, the higher the rating (from either test) the more durable the fabric is purported to be.  It’s not unusual for designers today to ask for 100,000 WZ results.  Is this because we think more is always better?  Does a test of 1,000,000 WZ guarantee that your fabric will survive years longer than one rated only 100,000 WZ?  Maripaul Yates, in her guidebook for interior designers, says that “test results are so unreliable and the margin of error is so great that its competency as a predictor of actual wear is questionable.”[4]  The Association for Contract Textiles website states that “double rubs exceeding 100,000 are not meaningful in providing additional value in use.  Higher abrasion resistance does not necessarily indicate a significant extension of the service life of the fabric.”

And of course, any company can skew results in their favor.  This is an image I found on Google images, with abrasion test results from a company selling leather motorcycle clothing.  They did say that “leather will sometimes score up to 100,000 cycles or so on the Wyzenbeek test, but testing to destruction (over 50k cycles) doesn’t always prove much.”  No comment on these results !

There are, apparently, many ways to tweak test results. We’ve been told if we don’t like the test results from one lab, we can try Lab X, where the results tend to be better.  The reasons that these tests produce inconsistent results are:

  1. Variation in test methods:       Measuring the resistance to abrasion is very complex.  Test results are affected by many factors that include the properties and dimensions of  the fibers; the structure of the yarns; the construction of the fabrics;  the type, kind and amount of treatments added to the fibers, yarns, or      fabric; the time elapsed since the abradant was changed;  the type of  abradant used; the tension of the specimen being tested,the pressure between the abradant and the specimen…and other variables.
  2. Subjectivity:    The  measurement of the relative amount of abrasion can be affected by the method of evaluation and is often influenced by the judgment of the operator.  Cycles to rupture, color change, appearance change and so forth are highly variable parameters and subjective.
  3. Games Playing:     Then there is, frankly, dishonest collusion between the tester and the testee.  There are lots of games that are played. For instance, in Wyzenbeek, the abradant, either cotton duck or a metal screen, must be replaced every million double rubs. If your fabric is tested at the beginning of that abradant’s life versus the end of its life, well.. you can see the games. Also, how much tension the subject fabric is under –  the “pull” of the stationary anchor of the subject fabric, affects the  rating.

In the final analysis, if you have doubts about the durability of a fabric,  will any number of test results convince you otherwise?  Also, if your heart is set on a silk  jacquard, for example, I bet it would take a lot of data to sway you from your heart’s desire.  Some variables just trump the raw data.

REFERENCES FOR WEAVE STRUCTURE:

1.  Peirce, F.T., The Geometry of Cloth Structure, “The Journal of the Textile Institute”, 1937: pp. 45 – 196

2. Brierley, S. Cloth Settings Reconsidered The Textile Manufacturer 79 1952: pp. 349 – 351.

3. Milašius, V. An Integrated Structure Factor for Woven Fabrics, Part I: Estimation of the Weave The Journal of the Textile Institute 91 Part 1 No. 2 2000: pp. 268 – 276.

4. Kumpikaitė, E., Sviderskytė, A. The Influence of Woven Fabric Structure on the Woven Fabric Strength Materials Science (Medžiagotyra) 12 (2) 2006: pp. 162 – 166.

5. Frydrych, I., Dziworska, G., Matusiak, M. Influence of Yarn Properties on the Strength Properties of Plain Fabric Fibres and Textile in Eastern Europe 4 2000: pp. 42 – 45.

6. ISO 13934-1, Textiles – Tensile properties of fabrics – Part 1: Determination of Maximum Force and Elongation at Maximum Force using the Strip Method, 1999, pp. 16.


[1] Tallant, John, Fiori, Louis and Lagendre, Dorothy, “The Effect of the Short Fibers in a Cotton on its Processing Efficiency and Product Quality”, Textile Research Journal, Vol 29, No. 9, 687-695 (1959)

[3] ‘How will Performance Fabrics Behave”, Home & Design,  The Philadelphia Inquirer, April 11, 2008.

[4] Yates, Maripaul, “Fabrics: A Guide for Interior Designers and Architects”, WW. Norton and Company.





The case for natural fibers

26 06 2012

I’m going to be taking a few weeks off,  and thought I’d recycle some of our old posts.  So if you think you’ve seen these before – you have.   But the issues remain important and it doesn’t hurt to remind you.    I’ve updated the topics a bit if necessary.

Since the 1960s, the use of synthetic fibers has increased dramatically,  causing the natural fiber industry to lose much of its market share.  Polyester – especially recycled polyester – became the fabric of choice in the United States.   It was cheap, and oil was plentiful.  But with with dawning realization that the party might be over, polyester prices – and those of other synthetics – will reflect climbing oil prices, so the price of synthetics may equal those of natural fibers.

International Forum for Cotton Promotion

Natural fibers  have a history of being considered the highest quality fibers, valued for their comfort, soft hand and versatility.  They also carry a certain cachet:  cashmere, silk taffeta and 100% pure Sea Island cotton convey different images than does 100% rayon,  pure polyester or even Ultrasuede, don’t they?  And natural fibers, being a bit of an artisan product, are highly prized especially in light of campaigns by various trade associations to brand its fiber:   “the fabric of our lives” from Cotton, Inc. and merino wool with the pure wool label are two examples. 

Preferences for natural fibers seem to be correlated with income; in one study, people with higher incomes preferred natural fibers by a greater percentage than did those in lower income brackets.   Cotton Incorporated funded a study that demonstrated that  66% of all women with household incomes over $75,000 prefer natural fibers to synthetic.

What are the reasons, according to the United Nations, that make natural fibers so important?  As  the UN website, Discover Natural Fibers says:

  1. Natural fibers are a healthy choice.
    1. Natural fiber textiles absorb perspiration and release it into the air, a process called “wicking” that creates natural ventilation. Because of their more compact molecular structure, synthetic fibers cannot capture air and “breathe” in the same way. That is why a cotton T-shirt is so comfortable to wear on a hot summer’s day, and why polyester and acrylic garments feel hot and clammy under the same conditions. (It also explains why sweat-suits used for weight reduction are made from 100% synthetic material.) The bends, or crimp, in wool fibers trap pockets of air which act as insulators against both cold and heat – Bedouins wear thin wool to keep them cool. Since wool can absorb liquids up to 35% of its own weight, woollen blankets efficiently absorb and disperse the cup of water lost through perspiration during sleep, leaving sheets dry and guaranteeing a much sounder slumber than synthetic blankets.
    2. The “breathability” of natural fiber textiles makes their wearers less prone to skin rashes, itching and allergies often caused by synthetics. Garments, sheets and pillowcases of organic cotton or silk are the best choice for children with sensitive skins or allergies, while hemp fabric has both a high rate of moisture dispersion and natural anti-bacterial properties.   Studies by Poland’s Institute of Natural Fibers have shown that 100% knitted linen is the most hygienic textile for bed sheets – in clinical tests, bedridden aged or ill patients did not develop bedsores. The institute is developing underwear knitted from flax which, it says, is significantly more hygienic than nylon and polyester. Chinese scientists also recommend hemp fiber for household textiles, saying it has a high capacity for absorption of toxic gases.
  2. Natural fibers are a responsible choice.
    1. Natural fibers production, processing and export are vital to the economies of many developing countries and the livelihoods of millions of small-scale farmers and low-wage workers. Today, many of those economies and livelihoods are under threat: the global financial crisis has reduced demand for natural fibers as processors, manufacturers and consumers suspend purchasing decisions or look to cheaper synthetic alternatives.
    2. Almost all natural fibers are produced by agriculture, and the major part is harvested in the developing world.
      1. For example, more than 60% of the world’s cotton is grown in China, India and Pakistan. In Asia, cotton is cultivated mainly by small farmers and its sale provides the primary source of income of some 100 million rural households.
      2. In India and Bangladesh, an estimated 4 million marginal farmers earn their living – and support 20 million dependents – from the cultivation of jute, used in sacks, carpets, rugs and curtains. Competition from synthetic fibers has eroded demand for jute over recent decades and, in the wake of recession, reduced orders from Europe and the Middle East could cut jute exports by 20% in 2009.
      3. Silk is another important industry in Asia. Raising silkworms generates income for some 700 000 farm households in India, while silk processing provide jobs for 20 000 weaving families in Thailand and about 1 million textile workers in China. Orders of Indian silk goods from Europe and the USA are reported to have declined by almost 50% in 2008-09.
      4. Each year, developing countries produce around 500 000 tonnes of coconut fiber – or coir – mainly for export to developed countries for use in rope, nets, brushes, doormats, mattresses and insulation panels. In Sri Lanka, the single largest supplier of brown coir fiber to the world market, coir goods account for 6% of agricultural exports, while 500 000 people are employed in small-scale coir factories in southern India.
      5. Across the globe in Tanzania, government and private industry have been working to revive once-booming demand for sisal fiber, extracted from the sisal agave and used in twine, paper, bricks and reinforced plastic panels in automobiles. Sisal cultivation and processing in Tanzania directly employs 120 000 people and the sisal industry benefits an estimated 2.1 million people. However, the global slowdown has cut demand for sisal, forced a 30% cut in prices, and led to mounting job losses.
  3. Natural fibers are a sustainable choice.
    1. Natural fibers will play a key role in the emerging “green” economy based on energy efficiency, the use of renewable feed stocks in bio-based polymer products, industrial processes that reduce carbon emissions and recyclable materials that minimize waste.  Natural fibers are a renewable resource, par excellence – they have been renewed by nature and human ingenuity for millennia. They are also carbon neutral: they absorb the same amount of carbon dioxide they produce. During processing, they generate mainly organic wastes and leave residues that can be used to generate electricity or make ecological housing material. And, at the end of their life cycle, they are 100% biodegradable.
    2. An FAO study estimated that production of one ton of jute fiber requires just 10% of the energy used for the production of one ton of synthetic fibers (since jute is cultivated mainly by small-scale farmers in traditional farming systems, the main energy input is human labor, not fossil fuels).
    3. Processing of some natural fibers can lead to high levels of water pollutants, but if the processing is done to Global Organic Textile Standards, it consists mostly of biodegradable compounds, in contrast to the persistent chemicals, including heavy metals, released in the effluent from synthetic fiber processing.
    4. The environmental benefits of natural fiber products accrue well beyond the production phase. For example, fibers such as hemp, flax and sisal are being used increasingly as reinforcing in place of glass fibers in thermoplastic panels in automobiles. Since the fibers are lighter in weight, they reduce fuel consumption and with it carbon dioxide emissions and air pollution.
    5. But where natural fibers really excel is in the disposal stage of their life cycle. Since they absorb water, natural fibers decay through the action of fungi and bacteria. Natural fiber products (processed organically)  can be composted to improve soil structure, or incinerated with no emission of pollutants and release of no more carbon than the fibers absorbed during their lifetimes. Synthetics present society with a range of disposal problems. In land fills they release heavy metals and other additives into soil and groundwater. Recycling requires costly separation, while incineration produces pollutants and, in the case of high-density polyethylene, 3 tonnes of carbon dioxide emissions for every tonne of material burnt. Left in the environment, synthetic fibers contribute, for example, to the estimated 640 000 tonnes of abandoned fishing nets and gear in the world’s oceans.
  4. Natural fibers are a high-tech choice.
    1. Natural fibers have intrinsic properties – mechanical strength, low weight  – that have made them particularly attractive to the automobile industry.
      1. In Europe, car makers are using mats made from abaca, flax and hemp in press-molded      thermoplastic panels for door liners, parcel shelves, seat backs, engine shields and headrests.
        1. For consumers, natural fiber composites in automobiles provide better thermal and acoustic insulation than fiberglass, and reduce irritation of the skin and respiratory system. The low density of plant fibers also reduces vehicle weight, which cuts fuel consumption.
        2. For car manufacturers, the moulding process consumes less energy than that of fibreglass and produces less wear and tear on machinery, cutting production costs by up to 30%.  German companies lead the way. Daimler-Chrysler has developed a flax-reinforced polyester composite, and in 2005 produced an award-winning spare wheel well cover that incorporated abaca yarn from the Philippines. Vehicles in some BMW series contain up to 24 kg of flax and sisal. Released in July 2008, the Lotus Eco Elise (pictured above) features body panels made with hemp, along with sisal carpets and seats upholstered with hemp fabric. Japan’s carmakers, too, are “going green”. In Indonesia, Toyota manufactures door trims made from kenaf and polypropylene, and Mazda is using a bioplastic made with kenaf for car interiors.
    1. Worldwide, the construction industry is moving to natural fibres for a range of products, including light structural walls, insulation materials, floor and wall coverings, and roofing. Among recent innovations are cement blocks reinforced with sisal fibre, now being manufactured in Tanzania and Brazil. In India, a growing shortage of timber for the construction industry has spurred development of composite board made from jute veneer and coir ply – studies show that coir’s high lignin content makes it both stronger and more resistant to rotting than teak. In Europe, hemp hurd and fibres are being used in cement and to make particle boards half the weight of wood-based boards. Geotextiles are another promising new outlet for natural fibre producers. Originally developed in the Netherlands for the construction of dykes, geotextile nets made from hard natural fibres strengthen earthworks and encourage the growth of plants and trees, which provide further reinforcement. Unlike plastic textiles used for the same purpose, natural fibre nets – particularly those made from coir – decay over time as the earthworks stabilize.
  1. Natural fibers are a fashionable choice.
    John Patrick Organic Fall/Winter 2010
    1. Natural fibers are at the heart of a fashion movement that goes by various names: sustainable, green, uncycled, ethical, eco-, even eco-environmental. It focuses fashion on concern for the environment, the well-being of fiber producers and consumers, and the conditions of workers in the textile industry. Young designers now offer “100% carbon neutral” collections that strive for sustainability at every stage of their garments’ life cycle – from production, processing and packaging to transportation, retailing and ultimate disposal. Preferred raw materials include age-old fibres such as flax and hemp, which can be grown without agrochemicals and produce garments that are durable, recyclable and biodegradable. Fashion collections also feature organic wool, produced by sheep that have not been exposed to pesticide dips, and “cruelty-free” wild silk, which is harvested – unlike most silk – after the moths have left their cocoons.
    2. The Global Organic Textile Standard (GOTS)   sets strict standards on chemicals permitted in processing, on waste water treatment, packaging material and technical quality parameters, on factory working conditions and on residue testing.
    3. Sustainable fashion intersects with the “fair trade” movement, which offers producers in developing countries higher prices for their natural fibres and promotes social and environmental standards in fibre processing. Fair trade fashion pioneers are working with organic cotton producers’ cooperatives in Mali, hand-weavers groups in Bangladesh and Nepal, and alpaca producers in Peru. A major UK chain store launched in 2007 a fair trade range of clothing that uses cotton “ethically sourced” from farmers in the Gujarat region of India. It has since sold almost 5 million garments and doubled sales in the first six months of 2008.
    4. Another dimension of sustainable fashion is concern for the working conditions of employees in textile and garment factories, which are often associated with long working hours, exposure to hazardous chemicals used in bleaching and dyeing, and the scourge of child labor. The recently approved (November 2008) Global Organic Textile Standard, widely accepted by manufacturers, retailers and brand dealers, includes a series of “minimum social criteria” for textile processing, including a prohibition on the use of child labor, workers’ freedom of association and right to collective bargaining, safe and hygienic working conditions, and “living wages”.




Eucalyptus fiber by any other name

2 03 2012

Fibers are divided into three main categories:

  • Natural – like flax, wool, silk and cotton
  • Manufactured – made from cellulose or protein
  • Synthetic – made from synthetic chemicals

The difference between “manufactured” and “synthetic” fibers is that the manufactured fibers are derived from naturally-occurring cellulose or protein, while synthetic fibers are not.  And  manufactured fibers are unlike  natural fibers because they require extensive processing (or at least more than is required by natural fibers) to become the finished product.  The category of “manufactured” fibers is often called “regenerated cellulose” fibers.  Cellulose is a carbohydrate and the chief component in the walls of plants.

Rayon is the oldest manufactured fiber, having been in production since the 1880s in France, where it was originally developed as a cheap alternative to silk.   Most rayon production begins with wood pulp, though any plant material with long molecular chains is suitable.

There are several chemical and manufacturing techniques to make rayon, but the most common method is known as the viscose process. In the viscose process, cellulose is treated with caustic soda (aka: sodium hydroxide) and carbon disulfide, converting it into a gold, highly viscous  liquid about the color and consistency of honey.  This substance gives its name to the manufacturing process, called the viscose process.

The viscous fluid is allowed to age, breaking down the cellulose structures further to produce an even slurry, and is then filtered to remove impurities.  Then the mixture is forced through fine holes, called a spinerette, directly into a chemical bath where it hardens into fine strands. When washed and bleached these strands become rayon yarn.

Although the viscose process of making rayon from wood or cotton has been around for a long time, it wasn’t until 2003 that a method was devised for using bamboo for this process.(3)  Suddenly, bamboo was the darling of marketers, and the FTC had to step in to remind manufacturers to label their products as “bamboo viscose” rather than simply bamboo.

Now we hear about fabrics made from  eucalyptus, or soy.  But it’s the same story – the fibers are created using the viscose process.  Because the FTC did not specifically name these two substances in their proclamation regarding bamboo,   marketers can claim fabrics are  “made from eucalyptus”.    The reality is that the viscose process can produce fibers from any cellulose or protein source – chicken feathers, milk and even bacteria have been used (rayon comes specifically from wood or cotton).  But those inputs are not nearly as exciting to the marketers as eucalyptus or soy, so nobody has been advertising fibers made from bacteria.

After the brouhaha about bamboo viscose hit the press, many people did a quick scan of viscose and declared it “unsafe” for the environment.  The reason the viscose process is thought to be detrimental to the environment is based on the process chemicals used. Though sodium hydroxide is routinely used in the processing of organic cotton, and is approved by the Global Organic Textile Standard (GOTS), carbon disulfide can cause nervous system damage with chronic exposure.  And that “chemical bath” to harden the threads?  Sulfuric acid.  But these chemicals do not remain as a residue on the fibers – the proof of this is that almost all of the viscose produced can be (and often is) Oeko Tex certified (which certifies that the finished fiber has been tested for any chemicals which may be harmful to a person’s health and contains no trace of these chemicals.)

The environmental burden comes in disposing of these process chemicals: the sodium hydroxide (though not harmful to humans) is nevertheless harmful to the environment if dumped into our rivers as untreated effluent. Same with carbon disulfide  and, certainly, sulfuric acid.  And there are emissions of these chemicals as well, which contribute to greenhouse gasses.  And the reason that these fibers can be Oeko Tex certified:  Oeko Tex certifies only the final product, i.e.,the fibers or the fabric.  They do not look at the production process, which is where the majority of the environmental burden is found.  And then of course there is the weaving of these viscose fibers into fabric – if done conventionally, the environmental burden is devastating (in terms of chemical and water use) and the fabric itself probably contains many chemicals known to be harmful to our health.

Certainly the standard viscose production process is definitely NOT environmentally friendly, but then there is Tencel ® and Modal ®.   These fibers are manufactured by the Austrian company Lenzing, which  advertises its environmentally friendly production processes, based on closed loop systems.  Lyocell is the generic name for the fibers produced by Lenzing, which are not produced by the traditional viscose process but rather by solvent spinning.

According to Lenzing:

  • There is an almost complete recovery of the solvent, which both minimizes emissions and conserves resources.  Lenzing uses  a new non-toxic solvent (amine oxide) and the cellulose is dissolved in N-Methylmorpholine N-oxide rather than sulfuric acid. Water is also evaporated, and the resulting solution filtered and extruded as filaments through spinnerets into an aqueous bath. Over 99% of the solvent can washed from the fiber and purified for re-use. The water is also recycled.
  •  The by products of production, such as acetic acid, xylose and sodium sulphate are key ingredients in the food and glass industry. Remaining materials are used as energy for the Lenzing process.
  • Tencel ® is made from eucalyptus, which is grown on marginal land unsuitable for food crops; these trees are grown with a minimum of water and are grown using sustainable forestry initiatives.
  • The final fibers are biodegradable and can decompose in soil burial or in waste water treatment plants.

So Lenzing fibers can be considered a good choice if you’re looking for a sustainable fiber – in fact there is a movement to have Lenzing Tencel® eligible for GOTS certification, which we support, because the production of these fibers conforms with the spirit of GOTS.  They already have the EU Flower certification.

But Lenzing does not make fabrics – it sells yarns to mills and others which use the yarns to make fabric and other goods.

So  we’re back to the beginning again, because people totally forget about the environmental impact in the weaving of fibers into fabric, where the water and chemical use is very high –  if done conventionally, the environmental burden is devastating  and the finished fabric itself probably contains many chemicals which are outlawed in other products.

It’s critically important to look at both the fiber as well as the weaving in order to make a good choice.