To polyester or not to polyester

19 04 2016

Give our retail website, Two Sisters Ecotextiles, a look and let us know what you think.

We are pondering about whether to sell polyester fabrics – largely because people are insisting on it. And there is a lot of polyester being produced:

polyester production

But, when (or if) we sell polyester fabric or blends, we have determined that the fabric must be GRS Gold level certified polyester, because:

  1. GRS is to synthetics as GOTS is to natural fibers.  It is our assurance:
    1. that there is water treatment in place,
    2. that no toxic additives are used as process chemicals, and no finishes (such as fire retardants or stain repellants) are added to the fabric,
    3. and that workers have basic rights.
  2. GRS provides verified support for the amount of recycled content in a yarn. It provides a track and trace certification system that ensures that the claim a fabric is made from recycled polyester can be officially backed up. Today, the supply chains for recycled polyester are not transparent, and if we are told that the resin chips we’re using to spin fibers are made from bottles – or from industrial scrap or old fleece jackets  – we have no way to verify that.  Once the polymers are at the melt stage, it’s impossible to tell where they came from.  So the yarn/fabric could be virgin polyester or it could be recycled.   Many so called “recycled” polyester yarns may not really be from recycled sources at all because – you guessed it! – the  process of recycling is much more expensive than using virgin polyester.  Unfortunately not all companies are willing to pay the price to offer a real green product, but they sure do want to take advantage of the perception of green.   So when you see a label that says a fabric is made from 50% polyester and 50% recycled polyester – well, (until now) there was absolutely no way to tell if that was true. In addition,

The Global Recycle Standard (GRS), originated by Control Union and now administered by Textile Exchange (formerly Organic Exchange), is intended to establish independently verified claims as to the amount of recycled content in a yarn, with the important added dimension of prohibiting certain chemicals, requiring water treatment and upholding workers rights, holding the weaver to standards similar to those found in the Global Organic Textile Standard:

  • Companies must keep full records of the use of chemicals, energy, water consumption and waste water treatment including the disposal of sludge;
  • All prohibitied chemicals listed in GOTS are also prohibited in the GRS;
  • All wastewater must be treated for pH, temperature, COD and BOD before disposal (It’s widely thought that water use needed to recycle polyester is low, but who’s looking to see that this is true?  The weaving, however, uses the same amount of water (about 500 gallons to produce 25 yards of upholstery weight fabric) – so the wastewater is probably expelled without treatment, adding to our pollution burden)
  • There is an extensive section related to worker’s rights.

Polyester is much (much, much, much!) cheaper than natural fibers and it wears like iron – so you can keep your sofa looking good for 30 years. The real question is, will you actually keep that sofa for 30 years?

There is still a problem with the production of synthetics. Burgeoning evidence about the disastrous consequences of using plastic in our environment continues to mount. A new compilation of peer reviewed articles, representing over 60 scientists from around the world, aims to assess the impact of plastics on the environment and human health [1] But synthetics do not decompose: in landfills they release heavy metals, including antimony, and other additives into soil and groundwater. If they are burned for energy, the chemicals are released into the air.

Also please keep in mind, that, if you choose a synthetic, then you bypass the benefits you’d get from supporting organic agriculture, which may be one of our most potent weapons in fighting climate change, because:

    1. Organic agriculture acts as a carbon sink: new research has shown that what is IN the soil itself (microbes and other soil organisms in healthy soil) is more important in sequestering carbon that what grows ON the soil. And compared to forests, agricultural soils may be a more secure sink for atmospheric carbon, since they are not vulnerable to logging and wildfire. The Rodale Institute Farming Systems Trial (FST) soil carbon data (which covers 30 years) demonstrates that improved global terrestrial stewardship–specifically including regenerative organic agricultural practices–can be the most effective currently available strategy for mitigating CO2 emissions.
    2. It eliminates the use of synthetic fertilizers, pesticides and genetically modified organisms (GMOs) which is an improvement in human health and agrobiodiversity
    3. It conserves water (making the soil more friable so rainwater is absorbed better – lessening irrigation requirements and erosion)
    4. It ensures sustained biodiversity

We’re not great fans of synthetics: Polyester is made from crude oil, and is the terminal product in a chain of very reactive and toxic precursors.   The manufacturing process requires workers and our environment to be exposed to some or all of the chemicals produced during the manufacturing process. There is no doubt that the manufacture of polyester is an environmental and public health burden that we would be better off without.

But there is a great quantity of existing polyester on this Earth, and there is only so much farmland that is available for cotton and other fiber crops, even though we have enough land to grow all the food and fiber we like, at least in theory.[2]

The biggest drawback to polyester production is that it requires a lot of energy, which means burning fuel for power and contributing to climate change. But to put that in perspective, Linda Greer, director of the health program at the Natural Resources Defense Council, says you actually release more carbon dioxide burning a gallon of gas than producing a polyester shirt.

However factories where polyester is produced which do not have end-of-pipe wastewater treatment systems release antimony along with a host of other potentially dangerous substances like cobalt, manganese salts, sodium bromide, and titanium dioxide into the environment.

In theory, cotton is biodegradable and polyester is not. But the thing is, the way we dispose of clothing makes that irrelevant. For cotton clothes to break down, they have to be composted, which doesn’t happen in a landfill.

The bottom line is that while the rise of polyester is not good news for the planet, a big increase in cotton production wouldn’t be any better, according to many sources: Both fabrics are created in huge factory plants, both go trough multiple chemical processes to make the final product, and both will be shipped around the globe.         (https://www.sewingpartsonline.com/blog/411-cotton-vs-polyester-pros-cons/)

But we keep returning to one point: there are already polyester bottles in existence. World demand for polyester in 2014 was a bit more than 46 million tons.[3] Only a small percentage of that is used for bottles, but that’s still a lot of bottles – in the United States, more than 42 billion bottles of water (only water!) were produced in 2010.[4] Doesn’t it make sense to re-use some of these bottles?

Mulling over the possibilities. Let us know how you feel.

[1] “Plastics, the environment and human health”, Thompson, et al, Philosophical Transactions of the Royal Society, Biological Sciences, July 27, 2009

[2] Atkisson, Alan, “Food, Fuel and Fiber? The Challenge of Using the Earth to Grow Energy”, December 2008, worldchanging.com

[3] Carmichael, Alasdair “Man made Fibers Continue to Grow”, Textile World, http://www.textileworld.com/Issues/2015/_2014/Fiber_World/Man-Made_Fibers_Continue_To_Grow

[4] http://www.container-recycling.org/images/stories/BUfigures/figure-pngs-new/figure4.png

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Breast cancer and acrylic fibers

16 09 2010

Just in case you missed the recent report which was published in Occupational and Environmental Medicine [1], 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.

I found it interesting that the researchers justified their findings because “synthetic fibers are typically treated with several chemicals, such as flame retardants from the organophosphate family, delustering agents, and dyes, some of which have estrogenic properties and may be carcinogenic.”

These are the same organophosphate flame retardants and dyes that are used across the textile spectrum, and which are found in most textiles that we surround ourselves with each day.

But also let’s look at the fibers themselves.  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.(2)

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

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.

Of course, there are the usual caveats about the study, and those commenting on it said further studies were needed since chance or undetected bias could have played a role in the findings. In addition, according to Reuters, “the scientists said more detailed studies focusing on certain chemicals were now needed to try to establish what role chemical exposure plays in the development of breast cancer.”  So this is yet another area in which more research needs to be done.  No surprise there.

But in the meantime, did you know that many popular fabrics are made of acrylic fibers?   One of the most popular is Sunbrella outdoor fabrics.     Sunbrella fabrics have been certified by GreenGuard Children and Schools because the chemicals used in acrylic production are bound in the polymer – in other words, they do not evaporate.   So Sunbrella fabrics do not contribute to poor air quality, (you won’t be breathing them in), but there is no guarantee that you won’t absorb them through your skin.  And you would be supporting the production of more acrylic, the production of which is not a pretty thing.

And what about backings on fabrics?  Many are made of acrylic.  Turn those fabric samples over and see if there is a plastic film on the back – it’s often made of acrylic.  Upholsterers like fabrics to be backed because it makes the process much easier and stabilizes the fibers.

So I don’t know about you, but I think I’ll avoid those synthetics for now – at least until we know where we stand.


[1] 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

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





What are PBDE’s and why should I be concerned?

21 07 2010

PBDE’s are chemical compounds that are used as flame retardants.  They can be found in almost anything that carries an electrical current or is highly flammable.  They’re in, for example, your TV, your computer, your cellphone,  your car, your toaster and your sofa. 

PBDE stands for polybrominated diphenyl ether – a compound which contains bromine atoms.  PBDE’s come in different forms, depending on the number and location of the bromine atoms.   There are 209 possible variations.  Often in the U.S. PBDE’s are marketed with trade names such as DE-60F or Saytex 102E (among others).  Variations of the polybrominated diphenyl ethers (PBDE’s)  include pentabrominated diphenyl ethers (pentaBDE’s); octabrominated diphenyl (octaBDE) and decabrominated diphenyl ethers (decaBDE’s).   Penta and Octa BDE’s are on the way out worldwide (are actually no longer produced in the US), but the chemical industry is waging a fierce fight to retain the use of the third major PBDE compound, Deca, which is the most widely used of the PBDE’s – about 50 million pounds a year in the U.S. alone.

PBDEs are released into the environment during manufacturing operations, as products containing these chemicals degrade, or when the products containing the PBDE’s  are disposed.

WHY SHOULD I BE CONCERNED?

SHORT ANSWER:   PBDE’s are everywhere, they accumulate and they spread.  And they’re really not good for us.

LONGER ANSWER:

Demand for flame retardants is up:  The average “escape time” that a person has to get out of a burning home has dropped from 17 minutes in 1975 to only 3 minutes today, according to a study by Underwriters Laboratories released in October 2007.  The reason for this is that plastics, from which so much of our consumer products are made, are made from oil, which is actually considered an accelerant in fires.  And synthetic fabrics (according to the UL study) produce hotter fires and more toxic smoke than natural fiber furnishings. The higher fire load of consumer products and home decorations has effectively made home fires so dangerous that fire alarms sounding will often not provide adequate time for occupants to escape. The flame retardants for plastics therefore have become more critical than ever before. Increasingly stringent fire codes and flammability requirements, especially in building materials and consumer products, are driving demand for flame retardants steadily higher.

PBDE use has increased 40% from 1992 to 2003, and is forecast to grow by at least 3% per year from 2011;   they are ubiquitous in consumer products.

Food is the major source of exposure for many contaminants, including DDT and PCBs.   But food doesn’t seem to be the culprit in this case: Since PBDEs are used as additive flame-retardantsand do not bind chemically to the polymers, they leach fromthe surface of the product and easily reach the environment.  In fact, The Environmental Working Group calculations show that dust is likely to be a more important PBDE exposure route for children than food, as PBDEs migrate from furniture and electronics into house dust.

And they don’t stay put:  Sit down on a foam cushion and you’re releasing countless, invisible PBDE particles. When the TV gets hot, still more escape and land in the dust in our homes. They rinse off our clothes in the laundry and run down the shower drain, winding up in sewage that’s applied to farm fields as fertilizer.

And what about all that plastic in the ocean gyres or in landfills?  It is slowly leaching PBDE’s.

These chemicals have characteristics that make them intrinsically hazardous to humans and other animals:  they are stable (persistent), they are fat seeking and they have the potential to act as endocrine disruptors.  What is meant by these sorta innocuous sounding terms is:

  1. persistent:  they bioaccumulate, or build up, in fish and cats and Orcas and foxes – and people.  Our bodies cannot get rid of these contaminates, so our levels just increase over time.  We eat PBDEs when they contaminate our food, particularly meat and dairy products. They latch on to dust and other particles, so we breathe them in, or ingest them when dust settles on food or when children stuff their fingers into their mouths. Scientists look for PBDEs in breast milk because the chemicals stick to fat. In 1999, Swedish researchers reported that PBDE levels in women’s breast milk had increased 60-fold between 1972 and 1997.  Similar dramatic increases were documented in California harbor seals, ringed seals from the Arctic, gull eggs from the Great Lakes and human blood from Norway.   PBDE pollution has been found essentially everywhere scientists have looked: in the tissues of whales, seals, birds and bird eggs, moose, reindeer, mussels, eels, and fish; in human breast milk, hair, fat and blood; in hot dogs and hamburgers and the cheese we put on them;  in twenty different countries and remote areas such as the North Sea, the Baltic Sea and the Arctic Ocean, on top of mountains and under the sea.
  2. fat seeking: this causes them to magnify up the food chain, increasing in concentration at each successively higher  level. Once PBDE’s are released into the environment, they invariably find their way into humans, including pregnant women, where they pass  to the developing fetus in utero or through the breast milk to the nursing infant.  As evidence of fetal exposure, the infant at birth has levels of PBDE’s that are up to 25% of maternal levels.  And researchers have found that children’s PBDE levels are about 2.8 times higher than their mothers. Research in animals shows that exposure to brominated fire retardants in-utero or during infancy leads to more significant harm than exposure during adulthood, and much lower levels of PBDEs are needed to cause harm to infants and children than to adults.
  3. endocrine disruptors: Many of the known health effects of PBDEs are thought to stem from their ability to disrupt the body’s thyroid hormone balance, which plays an essential role in brain development.  Laboratory animals showed deficits in learning and memory with exposure to PBDE’s.   Studies of mice showed that a single exposure to PBDEs caused permanent behavioral aberrations that worsened as the mice got older.  One study, for instance, found that women whose levels of T4 measured in the lowest 10 percent of the population during the first trimester of pregnancy were more than 2.5 times as likely to have a child with an IQ of less than 85 (in the lowest 20 percent of the range of IQs) and five times as likely to have a child with an IQ of less than 70, meeting the diagnosis of “mild retardation.”
    1. In addition to their effects on thyroid hormones and neurological development, PBDEs have been linked to a gamut of other health impacts in laboratory animals, from subtle to dramatic.  In-utero exposures have  been associated with serious harm to the fetus, including limb malformation, enlarged hearts, bent ribs,  delayed bone hardening, and lower weight gain. The malformations of the fetus were consistently seen at levels much lower than doses harmful to the mouse mothers.
    2. Only one commercial PBDE mixture has been tested for its ability to cause cancer, in a single study more than 15 years ago. High doses of Deca given to rats and mice caused liver, thyroid and pancreas tumors.

What does all of that mean, exactly?  

Personal choices can make a difference. Buying furniture, fabric, cell phones or computers made without PBDEs is definitely a vote for a non-toxic future. But personal choices can only go so far – and the crisis is great.   PBDEs, like other contaminant issues, are at least as much a social as a personal issue and challenge. You can help your kids not only with your buying habits, but also by modeling social action for environmental change, and by campaigning for a non-toxic future, the kind of future where mother’s milk will regain its purity.





Man-made synthetic fibers

7 07 2010

For millennia mankind depended on the natural world to supply its fiber needs.  But scientists, as a result of extensive research, were able to replicate naturally occurring animal and plant fibers by creating fibers from synthetic chemicals. In the literature, it is often noted that there are three kinds of man-made fibers: those made by “transformation of natural polymers” (also called regenerated cellulosics), those made from synthetic polymers and those made from inorganic materials (These include the fibers made of glass, metal, ceramics and carbon.) But by far the largest group of man made synthetic fibers being produced today are made from synthetic polymers, so we’ll concentrate on those in this post.

Man made  fibers from synthetic polymers  are created using polymerization of various chemical inputs to create polymers.  Polymerization is the process of combining many small molecules into a large molecule – a polymer.    Polymers are simply large molecules composed of repeating structural units.  Polymers used for synthetic fibers are produced from intermediates (which in turn have been produced from crude oil) and applying a catalyst.  Key intermediates are p-Xylene, teraphtalic acid, ethylene glycol and acrylonitrile;  catalysts – manganese, cobalt and antimony oxide –  are used to control the processes.

Polymers are the building blocks of synthetic fibers – and of many other things.   They are the basis of life and play an essential and ubiquitous role in our everyday life, ranging from familiar synthetic plastics to natural biopolymers such as DNA and proteins that are essential for life.  Natural polymeric materials such as shellac, amber and natural rubber have been in use for centuries. Biopolymers, such as proteins and nucleic acids, play crucial roles in biological processes. A variety of other natural polymers exist, such as cellulose, which is the main constituent of cotton and wood.

Synthetic polymers include vulcanized rubber, Bakelite and neoprene (and many more) in addition to polymers used in fibers:   polyester, nylon, polystyrene, polyethylene, PVC, and polyacrylonitrile (known as acrylic).

Synthetic fibers account for about half of all fiber usage, with applications in every field of fiber and textile technology.  Four synthetic fibers – nylon, polyester, acrylic and polyolefin – dominate the market. These four account for approximately 98% by volume of global synthetic fiber production.  But make no mistake, polyester is king:   polyester alone accounted for around 80% of the global market share of man made fibers.[1] Polyester has become the fiber of choice (sometimes blended with cotton) in garment production.  As recently as 1990, world polyester production totaled 20 billion pounds.  In 2002, production had more than doubled to 46 billion pounds – and was 61.5 billion pounds in 2009. [2] Polyester fiber consumption increased at an annual growth rate of 6.2% between 1998 and 2008,[3] although demand has recently moderated as a result of the global economic slowdown.

The raw materials used in synthetic production are mainly produced by large chemical companies which are sometimes integrated down to the crude oil refinery where p-Xylene is the base material used to produce other intermediaries.  For example p-Xylene is used to produce teraphtalic acid.   Major producers of teraphtalic acid include:

  • BP
  • Reliance (India-based Reliance just bought Trevira GmbH&Co)
  • Eastman Chemicals
  • Mitsui
  • Sinopec
  • SK-Chemicals

Among the world’s largest polyester producers are the following companies:

  • DuPont
  • Eastman
  • Invista
  • Wellman
  • M&G Group
  • Mitsui
  • Mitsubishi
  • Reliance
  • Teijin
  • Toray
  • Hyosung
  • Huvis
  • Jiangsu Hengli Chemical Fiber
  • Jiangsu Sanfangxian Industry
  • NanYa Plastics

Synthetic fiber production has definitely moved to Asian countries.   As stated in Textile World :   “the critical mass of fiber manufacturing from the industrialized West to the developing East is a study in comparative economics and social realities.”  In 1990, China represented barely 8% of total man-made production; by 2002 it produced almost 30% (almost a tie with the US and Europe).   India is also making a pitch to be a player: From a virtually nonexistent position in 1990 to currently 5%, with programs in place to expand this further.   According to Textile World, the world of polyester production has begun to resemble a monopoly, led by China.  “The speed with which Asia has dominated fiber production is astounding. The commitment is complete, and the world man-made fiber industry will never be the same – and that’s not necessarily a bad thing. It is obvious that production asset investments of the recent decade are world-class in efficiency and quality – with the world consumer receiving the benefits. The industrialized world must move on to a higher-return economy and let the developing world be satisfied by lower returns on investment, either through lower labor or local funds costs; or government-subsidized manufacturing aimed at employment, and/or accumulation of strong currencies to be used for continued economic development. Either way, the new nexus of the man-made fiber business is Asia.”

Since polyester is the king of synthetics (and because the data is available!) let’s look at how polyester is formed.

 

POLYMERIZATION:
First, the polymer is created; in the case of polyester, the polymer is made by heating either dimethyl teraphthalate (DMT)  or terephthalic acid (TPA) with ethylene glycol in the presence of a catalyst (ususally antimony) at 536 º F for 30 minutes at atmospheric pressure and then for 10 hours under vacuum. The excess of ethylene glycol is distilled off.  The resulting chemical, a monomer (single, non-repeating molecule) alcohol, is combined with terephthalic acid and raised to a temperature of 472°F (280°C). Newly-formed polyester, which is clear and molten, is extruded through a slot to form long ribbons.

DRYING: After the polyester emerges from polymerization, the long molten ribbons are allowed to cool until they become brittle. The material is cut into tiny chips and completely dried to prevent irregularities in consistency.

SPINNING:  Fibers are classified according to the type of spinning that the polymer undergoes: this can be melt spinning, dry spinning or wet spinning:

  1. Melt spinning is the simplest of these three methods:   In melt spinning, the polymer chips are melted at 500 – 518ºF to form a syrup-like solution.  The solution is put in a metal container called a spinneret and forced through its tiny holes. The number of holes in the spinneret determines the size of the yarn, as the emerging fibers are brought together to form a single strand. Melt spinning is used with polymers such as nylon, polyethylene, polyvinyl chloride, cellulose triacetate, and polyethylene terephthalate, and in the multifilament extrusion of polypropylene.
  2. Dry spinning:  the polymer is first dissolved in a solvent. The polymer solution  is then extruded through the spinnerets. The solvent is evaporated with hot air and collected for reuse. The fiber then passes over rollers, and is stretched to orient the molecules and increase the fiber strength. Cellulose acetate, cellulose triacetate, acrylic, modacrylic, aromatic nylon, and polyvinyl chloride are made by dry spinning.
  3. In wet spinning, the polymer solution (i.e., polymer dissolved in a solvent as in dry spinning) is spun into a coagulating solution to precipitate the polymer. This process has been used with acrylic, modacrylic, aromatic nylon, and polyvinyl chloride fibers.

For each pound of fiber produced with solvent spinning processes (dry or wet), a pound of polymer is dissolved in about 3 pounds of solvent.  So the capture and recovery of these solvents is an integral part of the solvent spinning process.  At present, most solvents are recovered, however emissions from the spinning operation are a significant consideration.  But air pollution emissions from polyester fiber production also include polymer dust from drying operations, volatilized residual monomer, fiber lubricants (in the form of fume or oil smoke) and the burned polymer and combustion products from cleaning the spinning equipment.

At the spinning stage, other chemicals may be added to the solution to achieve various effects such as making the material flame retardant, antistatic, or colorful (by adding dye chemicals).  Because these fibers are created from crude oil, they’re highly flammable (in fact, they’re considered an accelerant)  and pose a great threat for fire injury.  The development of a durable flame retardant for synthetics was key in the safe consumer use of synthetic fibers.

It is at the spinning stage that the two varieties of polyester fibers are created: filament and staple fibers:

  • FILAMENT:  When polyester emerges from the spinneret, it is soft and easily elongated up to five times its original length.  To create filament, the fibers are stretched.  The stretching forces the random polyester molecules to align in a parallel formation. This increases the strength, tenacity, and resilience of the fiber. This time, when the filaments dry, the fibers become solid and strong instead of brittle.   Stretched, or drawn,  fibers may vary greatly in diameter and length, depending on the characteristics desired of the finished material. Also, as the fibers are drawn, they may be textured or twisted to create softer or duller fabrics. After the polyester yarn is drawn, it is wound on large bobbins or flat-wound packages, ready to be woven into material.
  • STAPLE:  To create staple fiber, the spinneret has many more holes than when the production is filament fiber.  The rope like bundles of polyester that emerge are called tow.
    • Newly-formed tow is quickly cooled in cans that gather the thick fibers. Several lengths of tow are gathered and then drawn on heated rollers to three or four times their original length.
    • CRIMPING: Drawn tow is then fed into compression boxes, which force the fibers to fold like an accordion, at a rate of 9-15 crimps per inch (3-6 per cm). This process helps the fiber hold together during the later manufacturing stages.
    • SETTING: After the tow is crimped, it is heated at 212-302°F (100-150°C) to completely dry the fibers and set the crimp. Some of the crimp will unavoidably be pulled out of the fibers during the following processes.
    • CUTTING:  Following heat setting, tow is cut into shorter lengths. Polyester that will be blended with cotton is cut in 1.25-1.50 inch (3.2-3.8 cm) pieces; for rayon blends, 2 inch (5 cm) lengths are cut. For heavier fabrics, such as carpet, polyester filaments are cut into 6 inch (15 cm) lengths.

By and large, synthetic fibers are used for their utility in specific markets.

Polyester is difficult and expensive to dye, but has attributes that make it ideal for blending with cotton and other natural fibers.  Easy care of the permanent press fabric made polyester doubleknits extremely popular in the late 1960s.


However, polyester has suffered an “image problem” since that time, and clothes made out of polyester were often devalued and even ridiculed.  Polyester has the advantage of being very cheap to produce, but it is a much less attractive fiber to live with when compared to the inherent breathability, moisture absorption capabilities and heat moderation inherent in natural fibers.  Polyesters have the advantage in wash-and-wear properties, wrinkle resistance – and in durability.   Manufacturers tried to make polyester easier to use in garments by blending polyester with cotton, wool or other natural fibers.   Several new forms of polyester introduced in the early 1990s may help revitalize the image of polyester. A new form of polyester fiber, called microfiber, was introduced to the public in 1991.  Microfibers have diameters that are less than typical fibers; they are about half the diameter of fine silk fiber, one-quarter the diameter of fine wool, and one hundred times finer than human hair. Microfibers allow a fabric to be woven that is lightweight and strong. They can be tightly woven so that wind, rain, and cold do not easily penetrate. Rainwear manufactures use microfibers for this reason. They also have the ability to allow perspiration to pass through them. In addition, microfibers are very flexible because their small fibers can easily slide back and forth on one another. The first fabric made from microfiber was Ultrasuade, in which short polyester microfibers were imbedded into a polyurethane base. Today, microfibers are manufactured primarily from polyesters, nylon, and acrylic fibers. They are used under various trade names to make a variety of products, such as clothing, hosiery, bedding, and scarves.

Textile researchers at North Carolina State University are developing a form of polyester that may be as strong as Kevlar, a superfiber material used to make bulletproof vests.

Nylon, the granddaddy of man-made fibers, seems to be losing share to polyester, overwhelmed by sheer volume if not performance. In carpets, staple nylon gradually is being replaced by filament; tires increasingly use polyester over nylon; and many woven industrial and apparel fabrics seem to favor polyester. Nylon’s dyeability is an advantage, but not sufficiently so to overcome the supply and variants available in polyester.

Acrylic gradually is losing the price battle with polyester and increasingly is relegated to bulk and wool-substitute end-uses.


[1]http://www.officialwire.com/main.php?action=posted_news&rid=137418

[2] Luke, John; Fiber World: A Polyester Saga Geography and All; Textile World; http://www.textileworld.com/Articles/2004/September/Fiber_World/A_Polyester_Saga_Geography_And_All.html

[3] http://www.officialwire.com/main.php?action=posted_news&rid=137418