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Rayon: Types, Manufacturing Process of each Type, and Fabric Care

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

Rayon

Viscose Rayon

Viscose Rayon

All rayon fabrics are made from cellulose, such as wood pulp or cotton linters, but the way rayon is made makes the difference in the final product. Rayon fabrics can imitate natural fibers such as cotton, wool, silk, and linen.

The US Environmental Protection Agency (U.S. EPA) estimates that textile waste occupies approximately 5% of all landfills. To reduce pollution from textiles, try to choose environmentally friendly fabrics. Since rayon is made from cellulose, it is biodegradable. However, its production process causes some negative environmental impacts due to the carbon disulfide used in manufacturing most rayon fabrics.

The major manufacturing countries of rayon are China, Indonesia, India, America, Brazil, and some European countries.

In 2018, the world's viscose production reached about 5.8 million tons. China was the largest producer with about 65% of the total global production.

Rayon cuprammonium (Bemberg Rayon) looks like a silk texture. This kind of rayon is currently produced in limited countries.

The US Environmental Protection Agency has banned the manufacture of cuprammonium silk.

A Viscose Rayon spinning machine on display at the science museum in london.

A Viscose Rayon spinning machine on display at the science museum in london.

History

Artificial silk was first introduced in 1664. It was suggested that synthetic threads could be spun from a material similar to that produced by silkworms to make silk. Many scientists often tried this in the following years but were unsuccessful. In 1855, the French Georges Audemarte managed to create a thread by dipping a needle into a viscous solution of mulberry bark pulp and gum rubber. While interesting from a scientific point of view, this process was not economically viable as it was too slow and demands skill and accuracy.

Rayon's first patent was in 1855 by Swiss chemist George Audemars. Rayon was displayed at the Paris Exhibition in 1889 by French chemist Hilaire de Chardonnier, known as the father of the rayon industry, because he built the first commercial production plant for Chardonnett silk in Besancon, France.

In 1905, the English company Courtaulds produced regenerating cellulose called viscose rayon. Around 1908 French chemist Louis-Henri patented cuprammonium rayon. Courtaulds formed a branch in America called American Viscose Company, which began producing rayon in 1910.

Around 1918 the acetate silk manufactured at the British Celanese plant in Derbyshire, England. Roughly 24% of the rayon produced in the world in the 21st century comes from Grasim of India.

In 1951, modal rayon was first developed in Japan, and this type of rayon is nearly similar to the viscose rayon.

In the 1980s, lyocell rayon was developed in Courtaulds Research as a non-polluting alternative.

Currently, many rayon silks include bamboo instead of wood pulp. Because bamboo is fast-growing. A disadvantage of this process is that most bamboo rayon is made through the most polluted viscose process.

Viscose Rayon Production Line

rayon-types-manufacturing-process-and-fabric-care

Types of Rayon and the Manufacturing Process of each Type

There are many types of rayon, including viscose, acetate, lyocell, and modal rayons. Each type has a manufacturing method that gives it the final shape.

1- Viscose Rayon

Viscose Rayon has silk-like aesthetics and keeps its rich bright colors.

Manufacturing Process of viscose

Soaking: The cellulose core is dipped in 17-20% aqueous sodium hydroxide (NaOH) at a temperature of 18-25°C in order to swell the cellulose fibers and convert the cellulose into alkaline cellulose.

Compression: The swollen alkali cellulose mass is compressed to a wet weight equivalent to 2.5 to 3.0 times the weight of the original core to obtain an accurate ratio of alkali to cellulose.

Shredding: Pressed alkali cellulose is shredded mechanically to produce fine, well-divided particles called crumbs.

Aging: The alkali cellulose is aged under controlled conditions of time and temperature (18-30°C) in order to depolymerize cellulose to the required degree of polymerization. During this stage, the average molecular weight of the original core is reduced by a factor of two to three. Cellulose is reduced to obtain a viscose solution of correct viscosity and cellulose concentration.

Xanthation formation: At this stage, the aged alkali cellulose crumbs are placed in basins to react with carbon disulfide under a temperature (20 to 30°C) to form cellulose xanthate.

Solubility: The crumbs are dissolved in a caustic solution. The large xanthine substitutes on cellulose drive the chains to separate, reducing the hydrogen bonds between the chains and allowing water molecules to dissolve and separate the chains, resulting in an insoluble cellulose solution. Because of the non-xanthate cellulose clumps in the crystalline regions, the crumb is not completely soluble because the cellulose xanthate solution has a very high viscosity.

Ripening: The viscose is allowed to stand for a while to ripen. Two important processes occur during ripening: redistribution and loss of xanthate groups. The reversible xanthation reaction allows some xanthate groups to revert to hydroxyl cellulose and free CS2. This free CS2 can interact with another hydroxyl on other parts of the cellulose chain. In this way, the crystalline regions are gradually divided and a more complete solution is achieved. The lost CS2 reduces the solubility of cellulose and facilitates the regeneration of cellulose after it has been formed into filaments.

Filtering: The viscose is filtered to remove unsolved substances that may disrupt the spinning process.

Degassing: The air bubbles trapped in the viscose must be removed prior to extrusion, otherwise, they may cause weak spots in the fine rayon filaments.

Spinning: A solution of viscose is measured through a spinneret into a bath containing sulfuric acid (to acidify sodium cellulose xanthate), sodium sulfate (to impart a high salt content to the bath which is useful in the rapid coagulation of viscose), and zinc sulfate (exchanged with sodium xanthate to form zinc xanthate). Once the cellulose xanthate is neutralized and acidified, rapid coagulation of the rayon filament occurs followed by the simultaneous expansion and decomposition of cellulose xanthate to regenerated cellulose.

2- Acetate Rayon

While viscose silk is a regenerated fiber, rayon acetate is a regenerated modified fiber.

Manufacturing Process of Acetate

Acetylation process: Pre-treated purified cotton linters are fed into a closed container containing a mixture of acetic anhydride, glacial acetic acid, and a small amount of concentrated sulfuric acid may be used. For every 100 kg of cotton linters, 300 kg of glacial acetic acid, and 500 kg of acetic anhydride. The closed container consists of a metal tank with a round door at the top. The door is closed after adding the mixture of chemicals and cotton linters. The motor with many blades rotates in the acetylation to mix the ingredients well. Acetylation reaction is an exothermic reaction. Heat is removed by circulating cold water through a jacket attached to the closed container. The acetylation reaction is completed in 7-8 hours at 25-30°C. Triacetate is formed at this stage as a suspension in an acetylated mixture called an acid dope.

Hydrolysis: The acid dope is stored in jars for the aging, after that acetic acid, water, and sulfuric acid are added and leave for 10-20 hours. During the ripening period, the partial conversion of the acetate groups into the hydroxy groups occurs. The mixture is then diluted with water and stirred continuously when white flakes of rayon acetate had precipitated. The flakes are placed in a centrifuge and the excess water is ejected from the cage through the holes. Then the flakes are dried.

Spinning Process: The dope is spun into a rayon acetate yarn by a dry spinning process. The dope is fed from the spinning tank into spinning cabinets. The dope exiting the spindle travels 2-5 meters vertically downwards to the feed roller, where it is directed to the bobbin much faster than the spinning speed. This lends a twist to the filaments.

Mattress with lyocell as cover material.

Mattress with lyocell as cover material.

3- Lyocell Rayon

Lyocell fiber has featured as an important class of regenerated cellulose. It is produced based on the N-methyl morpholine-N-oxide (NMMO) dissolution method. It has unique properties compared to viscose fiber. The NMMO technology supplies a simple and environmentally friendly way for producing regenerated cellulose fiber.

Manufacturing Process of Lyocell

The manufacturing process for lyocell basically consists of five-steps:

Dissolution: This step involves breaking down the pulp fibers and mixing it with the solvent. The cellulose is dissolved in an aqueous system containing NMMO to form a highly viscous dope. The dissolving of the pulp of the lyocell is much simpler than that of the viscose process, as the dissolution of the dissolved pulp consists of the mercerization phase (soaking with sodium hydroxide), aging, and xanthation using carbon disulfide.

Filtration: The formed dope is filtered to remove coarse ingredients.

Spinning regeneration: The dope is extruded through the spinneret nozzle into an air gap, and then regenerated in a coagulation bath.

Washing: The resulting lyocell fibers are washed and the remaining NMMO recovered and recycled.

Finishing: This step is including bleaching, finishing, and drying.

4- The Modal Rayon

The modal rayon also is known as HWM rayon. This type of rayon is used in consumer textiles. The basic material for modal rayon is cellulose from hardwood trees such as oak and birch.

Manufacturing Process of Modal

Harvesting of trees: Trees like oak are split into small pieces roughly the size of a postage stamp and then transported onto the manufacturing floor. Then, these chips are purified to extract their cellulose content.

Steeping the sheets: The extracted cellulose is formed into sheets. These sheets are then dipped in baths of sodium hydroxide. Lower concentrations of NaOH are used to create modal rayon compared to concentrations of viscose silk, resulting in less toxic waste production.

Breaking into crumbs: After soaking is completed, the sheets are divided into crumbs. These crumbs are directly submerged in carbon disulfide, which turns the white crumbs into an orange substance called sodium cellulose xanthate. At this stage, tree-derived cellulose can no longer be considered a purely organic matter.

Forming into yarn: After that, cellulose xanthate is dipped in caustic soda again to create a syrup solution. The modal rayon production process once again bypasses the aging process that usually occurs at this stage. This syrup is immediately forced through a spinneret to form fibers.

Finishing: The fibers are then dipped in sulfuric acid, then stretched and formed into yarns. Then the resulting strands are washed, bleached, rinsed, dried, and loaded onto reels. During this stage, the modal yarn is ready for pre-shrinking, fireproof, wrinkle-proof, or a number of other treatments that can be applied before it is woven into the fabric.

Rayon Fabrics

Rayon Fabrics

Properties of Rayon

  • Rayon is soft, comfortable to the skin, and is resistant to abrasion. Like other cellulosic fibers, it is not elastic, which means it will wrinkle.
  • Rayon withstands lower ironing temperatures than cotton. It may be attacked by termites and silverfish, but is generally resistant to insect damage. Rayon is prone to rot.
  • Rayon fibers have the ability to blend easily with many fibers to reduce costs, or for luster, softness, and absorbency.
  • Rayon has moderate resistance to acids and alkalis. In general, the fibers themselves are not damaged by bleaching; however, the color of the dyes used in the fabric may change.
  • Viscose Rayon has silk-like aesthetics and keeps its rich bright colors. It is more moisture absorbent than cotton, dyed easily with bright colors, and does not produce static electricity.

Uses of Rayon

Rayon fibers are used to make shirts, blouses, dresses, jackets, underwear, scarves, suits, socks, towels, and hats.

Some rayon fibers are used for furnishings including bed sheets, blankets, curtains, and upholstery.

rayon-types-manufacturing-process-and-fabric-care

Tips to Care for Rayon Fabrics

  1. Some rayon manufacturing processes produce durable, fast-color fabrics that can be machine washable. But other processes produce a fabric that is best handled with care to prevent damage to the garment. This can be found out from the care label.
  2. While washing in the washing machine, turn the rayon clothes inside out and wash them in cold water on the delicate cycle with a low spin cycle.
  3. It is best not to dry rayon fabrics in the washing machine as they may be damaged. If you must, dry it on the lowest possible temperature cycle.
  4. During ironing, use medium heat as high temperatures can burn cellulosic fibers. Always iron on the wrong side of the fabric. For added protection, use a zip-cloth between the iron and the rayon fabric.
  5. When storing rayon fabrics, it is preferable to use materials that are resistant to moths and mildew.

Sources

https://www.ijera.com/papers/Vol2_issue5/DN25675680.pdf. Viscose Rayon: A Legendary Development in the Manmade Textile.

https://www.researchgate.net/publication/324597489_Regenerated_cellulose_by_the_lyocell_process_a_brief_review_of_the_process_and_properties.

https://www.patagonia.com/on/demandware.static/Sites-patagonia-us-Site/Library-Sites-PatagoniaShared/en_US/PDF-US/bamboo_rayon.pdf. Bamboo and Rayon.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2020 Eman Abdallah Kamel

Comments

Eman Abdallah Kamel (author) from Egypt on October 08, 2020:

Thank you very much, Liza. I appreciate your visit.

Liza from USA on October 08, 2020:

I remember when I was a kid, my mother used rayon fabric to sew to make a dress for my sister and me. My mother is a great seamstress. Thanks for sharing an educational article about the fabric, Eman. I enjoyed reading it.

Eman Abdallah Kamel (author) from Egypt on September 19, 2020:

I'm so glad that you liked the article, Chrish. Thanks for your kind comments.

Eman Abdallah Kamel (author) from Egypt on September 19, 2020:

It is my pleasure, Linda. Thanks for reading the article and comment.

Chrish Canosa from Manila Philippines on September 19, 2020:

Very interesting and helpful article Eman. I have been searching the right fur cloth for my stufed toys making (made of recycled shreded plastics) I have received my first order and I was disappointed for it is not the quality I expect. Hopefully the next one isn't a waste

I hope you have a fantastic day!

Linda Crampton from British Columbia, Canada on September 18, 2020:

Thank you for sharing so many facts about rayon, Eman. Your articles are very informative.

Eman Abdallah Kamel (author) from Egypt on September 18, 2020:

Thanks, Linda, for reading the article and comment.

Linda Chechar from Arizona on September 18, 2020:

Your great article about rayon fabric!

Eman Abdallah Kamel (author) from Egypt on September 18, 2020:

I am really glad, Lorna, that you liked the article. I also love to read history and always try to focus on the historical aspect of the article.

Thanks for reading the article and comment.

Lorna Lamon on September 18, 2020:

I enjoyed reading this excellent and informative article and in particular the historical past. I always learn something new from your articles Eman - thank you for sharing.

Eman Abdallah Kamel (author) from Egypt on September 18, 2020:

Thank you very much, Ankita, for reading the article and comment. I am so glad you enjoyed the article.

Ankita B on September 18, 2020:

Excellent article. It was truly informative and well structured. Thank you for sharing.