Synthetic Fibers: The Manufacturing Process and Risks to Human and Environment

Updated on January 5, 2019
Emmy ali profile image

Eman is a writer and textile engineer. She obtained her bachelor's degree in textile sciences from the Faculty of Applied Arts.

Synthetic Fiber

3D diagram showing the variants nylon 6 and nylon 6,6.
3D diagram showing the variants nylon 6 and nylon 6,6. | Source

Synthetic Fabrics

Synthetic fibers are man-made fibers. Most of the synthetic fibers are made from polymers produced by polymerization. Synthetic fibers are manufactured usually from oil, coal or natural gas.

The polymer is a chemical substance consisting of large molecules made from many smaller molecules: some polymers, such as nylon, are artificial. Proteins and DNA are natural polymers.

Sometimes cellulose (the main component of cotton fiber) and pulp of wood are used to make materials such as acetate and rayon (artificial silk).

Synthetic fabrics are the most prevalent in the world. China is the largest producer accounting for 70% of total global production. India is the second largest producer of synthetic fiber, but only 7.64% of global production comes from India while the European Union is the largest importer of synthetic filament fibers. The EU is followed by Turkey and the United States. Within the European Union, Germany and Italy are among the largest importers. There are many other importing countries such as the Middle East and African countries.

Although synthetic fibers are the most common and attractive, on the other hand, they are the most common fiber that causes diseases.

American Chemical Society has warned that synthetic fibers are ‘the biggest plastic pollution issue you haven’t heard of yet’.

Also, Swedish Chemicals Agency (Kemikalieinspektionen) has shown the risks of chemicals used in synthetic fabrics, especially in the finishing process and dyeing on humans and the environment.

History of Synthetic fibers

This poster is from the Swan Collection of Tyne & Wear Museums, held at the Discovery Museum in Newcastle upon Tyne.
This poster is from the Swan Collection of Tyne & Wear Museums, held at the Discovery Museum in Newcastle upon Tyne. | Source

In 1865, a French chemist Paul Schützenberger discovered cellulose acetate (acetate rayon) by the reaction of cellulose with acetic anhydride.

Around 1870, a French engineer Hilaire de Chardonnet invented the artificial silk which called Chardonnet silk.

In early 1880, the English inventor Josef Swan invented artificial fibers were drawn from cellulose liquid, formed by chemical modification, this fiber currently called semi-synthetic. The synthetic fibers produced by this process were chemically identical in their potential applications to Swan's carbon filament developed for his incandescent light bulb. Then Swan realized the fiber's ability to revolutionize the textile industry.

In 1905 the UK Company Courtaulds Fibers produced the first commercial viscose silk. In 1924 the name Rayon was adopted with the use of viscose in the viscous organic liquid used in the manufacture of rayon.

By 1894 the English chemist Charles Cross and his collaborators Edward Bevan and Clayton Beadle invented the viscose fiber which named by this name because of the highly viscous solution of xanthate produced from the reaction of carbon disulfide and cellulose in basic conditions.

The DuPont Rayon Plant

The DuPont rayon plant in Richmond in the 1930’s.
The DuPont rayon plant in Richmond in the 1930’s.

In 1905 the UK Company Courtaulds Fibers produced the first commercial viscose silk. In 1924 the name Rayon was adopted with the use of viscose in the viscous organic liquid used in the manufacture of rayon.

In the 1930s Wallace Carothers, an American researcher at the chemical firm DuPont developed nylon, the first synthetic fiber in the fully synthetic.

During 1941 the first polyester fibers were introduced by John Rex Winfield and James Tenant Dixon, British chemists who worked at the Calico Printers' Association. They produced the first polyester fiber known as the Dacron.

Around 1950, DuPont added acrylic fibers (plastic fibers) resembling wool.

In 1958, spandex or Lycra was invented by chemist Joseph Shivers at DuPont's Benger Laboratory in Waynesboro, Virginia. Lycra is stronger than natural rubber and used in the medical industries.

During 1965, Kevlar was developed by Stephanie Kwolek at DuPont. Kevlar is heat-resistant and used in bulletproof vests.

Kelvar

Golden yellow aramid fiber (Kevlar). The diameter of the filaments is about 10 µm. Melting point: none (does not melt). Decomposition temperature: 500-550 °C. Decomposition temperature in air: 427-482 °C (800-900 °F).
Golden yellow aramid fiber (Kevlar). The diameter of the filaments is about 10 µm. Melting point: none (does not melt). Decomposition temperature: 500-550 °C. Decomposition temperature in air: 427-482 °C (800-900 °F). | Source

Classification of Synthetic Fibers

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Synthetic Fabric

Stretching Polyester.
Stretching Polyester. | Source

Spinning of Synthetic Fiber

Manufacture Stages of Synthetic Fibers

Synthetic fibers can be manufactured in continuous filaments, which are infinite in length. A yarn can be made by assembling the filaments together continuously while producing threads.

An example of alkene polymerization, in which each styrene monomer's double bond reforms as a single bond plus a bond to another styrene monomer. The product is polystyrene.
An example of alkene polymerization, in which each styrene monomer's double bond reforms as a single bond plus a bond to another styrene monomer. The product is polystyrene. | Source

1- Polymerization is the reacting of small molecules together in a chemical reaction to form polymer chains. There are two types of polymerization: Condensation polymers are formed by the gradual reaction of functional groups of monomers, usually containing heterogeneous substances such as oxygen or nitrogen. An addition polymer is a mechanism in which monomers react to form a polymer without forming by-products. Addition polymerization processes are performed in the presence of catalysts.

2- Pumping: The molten polymer is pumped through a filter bed and then through small deep holes. Both units will lead to high-pressure drops along the flow direction of viscous liquids. There are two main devices used to pump liquids: centrifugal pumps and gear pumps. Centrifugal pumps are used to transport low viscosity liquids around in a process while gear pumps are used to pump highly viscous liquids at the controlled flow rate.

3- Filtration: It is cleaning the spinneret plate. The filtration process must be completed to very strict standards.

4- Spinning: The fibers are formed by extruding molten polymer through small holes in the spinneret plate. A plate may contain 1,000 or more holes. The filament thickness is not determined in linear dimensions but in terms of mass per length. There are three methods of spinning:

  • Melt spinning: In the spinning of molten polymers, such as polyester, nylon, and polypropylene. Once the molten polymer comes out of the spinneret hole, begins to cool down and also begins to stretch out. After application of finish, fibers are collected at high speed in a process known as spin drawing.
  • Dry spinning: In the process of dry spinning, solvents are used in which the polymer dissolves where a solvent evaporates after the solution (spine dope) leaves the spinneret. This process is followed by stretching, applying the finish and taking follow-up on the spindle or cutting into the staple. This process is more expensive than conventional melt spinning processes.
  • Wet spinning: This method is used for polymers that do not melt easily. The polymer dissolved in a solvent which extracted into a liquid (water) after the solution (spin dope) leaves the spinneret. The fibers are dried on large hot cylinders. The fibers are then sent to a cutter to cut fibers in lengths of 2.5-15 cm. The fibers produced by wet yarn include rayon, Kevlar, and acrylic fibers.

4- Drawing: Stretching, or drawing the filament is the process of pulling the long polymer chains to align along the longitudinal axis of fibers, grouping together and developing cohesion. During the drawing process, the polymer chains slide over each other as they are pulled to align along the longitudinal axis of the fibers.

Examples of textured yarns.

Source

Methods of Textured Yarns

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5- Texturing is the formation of curl, coils, and loops along the length of filaments to increase porosity, smoothness, and flexibility, from the methods of textured yarns :

  • Gear crimping: In order for staple fibers to be spun in yarns, they must have a crimp, similar to that of wool. This wrinkle may be mechanically inserted by passing the filament between gears or chemically by controlling the coagulation to create fibers with an asymmetrical cross-section, with one side with a thick-skinned, almost soft and the other thin-skinned and serrated. When wet, the fibers swell to a large extent on the skin-thin side rather than the thick-skinned side, causing the wrinkle.
  • Stuffing: Fiber yarns woven from very large bundles of fibers called a tow are typically zigzagged by feeding two of the tows in a stuffer box, where the tows are folded and pressed against each other to form a plug of the yarn. The plug can be heated by steam and when cooling, the filaments are curled.
  • Air-Jet: This method is performed by feeding yarns over a high-speed jet of air that forces the filament into loops. The textured yarns in this process contain a large number of very fine filaments, however, increasing the likelihood of tangled.
  • Knit de knit: This texturing produces a wavy shape like a knitted-loop. In this process, the yarn is knitted into a tubular fabric. The cloth is then heat set and subsequently unraveled to produce textured yarn.

False Twist Method

Source
  • False Twist: During this method, the filaments are twisted and heated, and then untwisted when cold, thus preserving the heat-set spiral shape of the Twist.

6- Finishing and dyeing: During the final process, synthetic fibers are processed with many chemicals to develop and improve their appearance. The dyes can be added to the molten solution before spinning the fibers. Fiber is usually dyed after spinning by pigments dissolved in boiling water baths. Synthetic fibers have a very coherent and intertwined structure because the molecular chains are regular and have a high degree of crystallization. The dye molecules settle in the spaces between the molecular chains. Depending on the nature of the synthetic fiber material, space varies in size from one type to another and notes that all synthetic fibers consist of materials that are not water-loving. Therefore, the dyeing rate depends on the internal structure of the fibers. We find that the dyeing rate is low in the case of synthetic fibers compared to other natural fibers so the time of dyeing is longer. To overcome this, auxiliary materials are added to the dye bath to help penetrate the fibers. Also increasing the temperature and pressure of some dyes increases the dyeing rate. For example, when dyeing polyester, a benzophenone (organic compound) is used to transfer or carry dyes into fibers under pressure. The carrier is used in a quantity of 0.05 to 1.2% by weight based on the dyeing solution. The popular dyes of synthetic fibers:

  • Disperse dyes are the only non-soluble dyes in the water that dyes polyester fibers and acetate. The disperse dye molecule is based on the azobenzene molecule or anthraquinone with an amine, nitro, or hydroxyl groups.
  • Fiber reactive dye can react with fiber directly. The chemical reaction takes place between the dye and the molecules of the fiber, making dye part of the fibers. These dyes are also used for dyeing natural fibers such as cotton and silk.
  • Basic dyes are also known as cationic dyes that act as bases when dissolved in water; they form a colorful cationic salt, which can react with anionic sites on fibers. Basic dyes produce bright, high-value parts on textile.
  • Acid dye is a dye that is usually applied to the fabric at low pH. They are mainly used for dyeing woolen fabrics. They are effective in dyeing nylon synthetic fibers.
  • Azo dyes are organic compounds carrying the functional group R−N=N−R′, where R and R' are usually aryls. Azo dyes are widely used for textile treatment.

Manufacturing of Synthetic Fiber

Synthetic Fabric

Uses of Synthetic Fiber

Synthetic fibers such as Polyester used in making coats, jackets, and ropes. Rayon used in bed sheets and carpets. Nylon is used in making seatbelts, ropes, and fishing nets. Spandex used in sportswear, belts bra straps, swimwear, shorts, gloves, skinny jeans, socks, underwear, and home furnishings such as microbead pillows.

Synthetic Fabric

Source

Risks of Synthetic Fibers to Human

Textile dermatitis is a skin reaction usually characterized by inflammation, redness, and itching in the skin after direct contact with synthetic fibers. There are two types of textile dermatitis: allergic and irritant. The allergic textile stimulates the immune system to a strange substance that penetrates the skin. The development of the allergic reaction occurs in two stages, the sensitization stage when the immune system recognizes the substance and mobilizes the response and the stage of induction when the immune system causes an allergic reaction which means the symptoms of allergic fiber dermatitis develop over time and not when the first contact with allergens. Irritant textile dermatitis occurs due to a substance that causes direct skin irritation and can occur when the first exposure of a substance. Epidemiological studies of textile dermatitis have indicated a significant number of patients with textile allergic. Textile dermatitis occurs mostly among consumers as upper body lesions, caused by wearing tight clothing from synthetic fibers. However, occupational exposure may also be a problem, especially hand lesions of wearing work gloves.

Hazardous chemicals used in the manufacture of synthetic fibers:

Polyester fibers are manufactured from both dihydric alcohol and terephthalic acid. Both are highly toxic and are not completely removed after the manufacturing process, resulting in easy access to the body through the wet skin, causing dermatitis in addition to respiratory infections.

Rayon is made from recycled wood pulp processed by carbon disulfide, sulfuric acid, ammonia, acetone, and caustic soda to withstand regular washing. Carbon dioxide emitted from Rayon's filaments can cause a headache, nausea, muscle pain and insomnia.

According to the Centers for Disease Control and Prevention, acrylonitrile enters our bodies through the skin by wearing garments made from acrylic fabric. Acrylonitrile is toxic in low doses. It is classified as a Category 2B carcinogen (possibly carcinogenic) by the International Agency for Research on Cancer. Acrylic is one of the causes of breast cancer in women. If the process of manufacturing acrylic is not carefully monitored it can lead to the explosion. Acrylic fibers are highly flammable.

Nylon relies on petroleum and receives many chemical treatments using caustic soda, sulfuric acid, and formaldehyde during manufacturing as well as bleaching and softening factors such as chloroform, pentane, limonene, and terpineol. Even after the manufacturing process, the fiber still retains toxins that can be harmful. Diseases associated with repeated wear of nylon clothes: allergy skin, dizziness, headache, spinal pain.

Spandex is manufactured by polyurethane dissolved in a dimethylformamide, dimethylacetamide or dimethyl sulfoxide. These strong chemicals make spandex wear for a long time cause skin allergies, impetigo, and folliculitis.

The risk of textile dyes:

A large European multi-center study found that 3.6% of the patients tested had a contact allergy to disperse dyes assessed as clinically relevant in one-third of cases and among these Disperse Blue 124, Disperse Blue 106, and Disperse Yellow 3.

Disperse dyes easily rub off from the fabric and migrate to the skin.

Another study found that about 25% of patients diagnosed as allergic to disperse dyes did not react with the dye molecule but with other substances in the dye. This suggests that commercial textile dyes may contain allergens that are not known to be identified. There are reports of epidemiological studies also reported that patients with textile dermatitis due to some reactive dyes, basic dyes, and acid dyes.

Cancer has been mainly linked to exposure to cancerous aryl amines which can be formed as a product of the division of azo dyes.

Hazardous chemicals used in the finishing process:

During the finishing process of textiles to improve the texture and quality of the fabric, many finishing resins release formaldehyde which can be emitted from the fabric and cause dermatitis. Many EU countries have national regulations on formaldehyde in textiles in order to reduce risks to human health. However, there are some reports indicating that there are still concerns about the release of formaldehyde fabric finishing resins. Epidemiological studies show that 2.3-8.2% of all textile dermatitis patients are sensitive to formaldehyde and a study shows that formaldehyde sensitivity is more common among people who have been exposed at work. Statistics from the European Union Rapid Alert System for the exchange of information on products that pose a serious health risk to consumers show that formaldehyde accounts for about 3% of all notifications of hazardous substances in textiles.

Water Pollution

Risks of Synthetic Fibers to the Environment

Synthetic fibers produced from petroleum such as polyester and nylon pose a significant risk to the environment because they are non-biodegradable.

Synthetic fiber industry is responsible for more than 20% of industrial water pollution in the world because the production of these fibers requires a lot of water, and contaminated water is pumped back after use into the oceans, seas, and rivers causing serious danger to aquatic organisms.

Nylon production emits nitrous oxide, which is very dangerous to the ozone layer 300 times more than carbon dioxide.

A study at the University of Plymouth in the UK analyzed what happened when a number of synthetic fabrics were washed at different temperatures in household washers, using different combinations of detergents, to determine the amount of microfibers shed. The researchers found that an average wash load of 6 kg could release an estimated 137,951 microfibers of polyester blended with cotton, 496,030 fibers of polyester and 728,789 of acrylics.

In that case, one of the considerations guiding policy intervention was the lack of clear societal benefit from incorporating microplastic particles into the cosmetics, coupled with concerns about environmental impacts. The societal benefits of textiles are without question and so any voluntary or policy intervention should be directed toward reducing emissions either via changes in textile design or filtration of effluent, or both.

— Professor Thompson, who leads the International Marine Litter Research Unit at Plymouth University.

The Story of Microfibers

In the next video, Bryan Clement, director of the Hippocrates Institute in West Palm Beach, Florida, discusses the dangers of chemicals in synthetic fabrics.

The Risks of Chemicals in Clothing

Fabrics

Solution to Reduce the Risk of Synthetic Fiber

After knowing the chemicals that used in the synthetic fibers from the beginning of manufacturing until the final processes and the great risk caused to humans and the environment, we should avoid these fibers as much as we can. I think the solution to reduce the production of chemical fibers is to return to nature and revive the production of natural fibers. On the other hand, consumers should try as much as possible to buy natural fibers such as cotton, linen, natural wool and other natural fabrics instead of synthetic fabrics.

Sources

Questions & Answers

  • What are some of the uses of synthetic fibers?

    Synthetic fibers such as Polyester is used in making ropes, jackets, raincoats, and nets.

    Nylon is used in ropes, parachutes, and fishing nets. Also, used in making seat belts, sleeping bags, socks, ropes, etc...

    Sometimes Rayon is mixed with wool to make carpet and mixed with cotton to make bedsheets...

Comments

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    • Emmy ali profile imageAUTHOR

      Eman Abdallah Kamel 

      8 months ago from Egypt

      Thank you, Mr. Holland, for these kind words. I hope we all go back to natural fibers away from synthetic as much as possible. I always appreciate your visit.

    • billybuc profile image

      Bill Holland 

      8 months ago from Olympia, WA

      I apologize for missing this article. I wonder if I'm getting notifications of your Hubs. Be that as it may, this was fascinating and very well-researched. I no longer buy synthetics....all natural for this boy. Every little bit helps, right?

    • Emmy ali profile imageAUTHOR

      Eman Abdallah Kamel 

      9 months ago from Egypt

      I agree with you, Linda. It is difficult to completely dispense with synthetic fibers because of they are the most common and least expensive but at least we try to be our clothes of natural fibers, especially the clothes of kids and newborn. I appreciate your visit.

    • lindacee profile image

      Linda Chechar 

      9 months ago from Arizona

      Thanks for this informational article, Emmy. I hadn't really thought about the dangers of synthetic fibers regarding health and environmental issues. Unfortunately, most of my clothing and furnishings are man-made textiles or at least a blend of natural fibers and synthetics. It will be difficult and expensive for me to make the move from synthetics to organic fabrics. You've given me a lot to think about!

    • Emmy ali profile imageAUTHOR

      Eman Abdallah Kamel 

      10 months ago from Egypt

      Thanks, Liz, synthetic fibers that are manufactured from plastic recycling are already worrying because of the diseases they cause to humans as well as risks to the environment. I appreciate your comment.

    • Eurofile profile image

      Liz Westwood 

      10 months ago from UK

      This is an interesting article. I was once at a woodland/eco park and saw an exhibition on recycling which seemed to suggest that fleece material clothing is made from recycling other products. Your article come up with some worrying information. In my youth Courtaulds was a well-known company in the UK.

    • Emmy ali profile imageAUTHOR

      Eman Abdallah Kamel 

      10 months ago from Egypt

      Thanks, Linda. In fact, synthetic fibers are alarming because they pose significant risks to humans and the environment. I always appreciate your visit.

    • AliciaC profile image

      Linda Crampton 

      10 months ago from British Columbia, Canada

      This is a great resource for people interested in synthetic fibers. The section on the risks of synthetic fibers to humans was eye-opening and worrying. Thank you for sharing the information.

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