Rayon, a semi-synthetic material, originates from natural sources like wood and agricultural products through the regeneration of cellulose. This fabric, also called viscose, shares cellulose’s molecular structure. Rayon, available in diverse types and grades, can replicate the feel and texture of other natural fibres like silk, wool, cotton, and linen. It’s frequently termed artificial silk when it resembles silk.
This adaptable fibre finds use in creating textiles for clothing and various other applications. In rayon production, cellulose undergoes solubilization, enabling the transformation of fibres into their desired shapes. Three common solubilization methods include the cuprammonium process, which uses ammoniacal solutions of copper salts; the viscose process, the most prevalent method, involving alkali and carbon disulfide; and the Lyocell process, which relies on amine oxide.
While the Lyocell process circumvents the neurotoxic carbon disulfide found in the viscose process, it tends to be more expensive. As a result, rayon’s sustainability as an eco-friendly fabric option for outdoor enthusiasts remains a topic of ongoing discussion.
From cellulose to comfort: the Rayon production techniques
Cellulose undergoes dissolution and conversion back into insoluble fibrous cellulose to create rayon. The cuprammonium method, viscose method, and lyocell process serve as the predominant techniques for this regeneration process.
Employed for over a century, these methods showcase their enduring presence in the textile industry.
The cuprammonium methods
Swiss chemist Matthias Eduard Schweizer (1818-1860) found that tetraamine copper dihydroxide could dissolve cellulose. In 1897, Max Fremery and Johann Urban developed a technique to create carbon fibres for use in light bulbs. The production of cuprammonium rayon for textiles commenced in 1899 at Vereinigte Glanzstoff Fabriken AG in Oberbruch near Aachen. In 1904, J.P. Bemberg AG made significant improvements that rendered artificial silk a viable alternative to genuine silk.
Cuprammonium rayon shares similar properties with viscose. During production, cellulose combines with copper and ammonia, forming Schweizer’s reagent. Owing to the adverse environmental effects of this method, some countries, including the United States, have ceased manufacturing cuprammonium rayon. Although considered a historical process, one company in Japan continues to produce cuprammonium rayon.
Another solvent used in this fabric’s production is tetraamminecopper(II) sulfate.
The viscose method
English chemist Charles Frederick Cross, along with his colleagues Edward John Bevan and Clayton Beadle, patented their artificial silk in 1894. They named the material “viscose” due to the highly viscous solution involved in its production. The process relied on the reaction of cellulose with a strong base and subsequent treatment with carbon disulfide to create a xanthate derivative. The xanthate is later converted back into cellulose fibre.
The UK-based Courtaulds Fibres manufactured the first commercial viscose rayon in November 1905. They established an American division called American Viscose (later known as Avtex Fibers) in 1910 to produce their formulation in the United States. The term “rayon” was coined in 1924, with “viscose” referring to the viscous organic liquid used in producing both rayon and cellophane. In Europe, however, the fabric itself became known as “viscose“, which the US Federal Trade Commission (FTC) has deemed an acceptable alternative name for rayon.
The viscose method uses wood as a cellulose source, while other rayon production techniques require lignin-free cellulose. This makes viscose more cost-effective, so it has traditionally been used on a larger scale than other methods. However, the original viscose process generated significant amounts of contaminated wastewater. Modern technologies have reduced water usage and improved wastewater quality. Until the 1930s, rayon was only produced as a filament fibre, but subsequent developments enabled the utilization of “broken waste rayon” as a staple fibre.
Structurally modified viscose
The physical properties of rayon remained consistent until the 1940s, when high-tenacity rayon was developed. Further advancements led to the creation of high-wet-modulus rayon (HWM rayon) in the 1950s, with research in the UK largely centred around the government-funded British Rayon Research Association.
High-tenacity rayon, a modified version of viscose, boasts nearly double the strength of HWM rayon and is commonly utilized for industrial purposes such as tire cords.
Around 1935, industrial applications of rayon surfaced, with the material replacing cotton fibres in tires and belts. Industrial rayon variants displayed a distinct set of properties, with tensile strength and elastic modulus being of utmost importance.
Modal, a genericized trademark of Lenzing AG, refers to a type of (viscose) rayon that is stretched during production to align the molecules along the fibres. Two forms of Modal are available: “polynosics” and “high wet modulus” (HWM).
HWM rayon, an enhanced form of viscose, exhibits increased strength when wet and can undergo mercerization similar to cotton. Known as “polynosic,” HWM rayons are dimensionally stable, resistant to wear, and maintain a soft, silky feel without shrinking or losing shape when wet. The trade name Modal is sometimes used to identify them.
Often used solo or blended with other fibres like cotton or spandex, Modal appears in clothing and household items such as pyjamas, underwear, bathrobes, towels, and bedsheets. Resistant to damage from tumble-drying, Modal exhibits less pilling than cotton due to its fibre properties and decreased surface friction. Derived from spinning beech-tree cellulose, Modal serves as a more environmentally friendly alternative to cotton, consuming 10–20 times less water on average during production.
The lyocell process is based on dissolving cellulose products in a solvent called N-methyl morpholine N-oxide (NMMO). This method is not as widespread, primarily due to its higher cost compared to the viscose process.
Originating from cellulose, the lyocell process employs dry jet-wet spinning and was developed by the now-defunct American Enka Company and Courtaulds Fibres. Lenzing’s Tencel serves as an example of a lyocell fibre.
A key distinction between the lyocell and viscose processes is that the former does not involve the highly toxic carbon sulfide. The term “Lyocell” has evolved into a genericized trademark used to describe the lyocell process for creating cellulose fibres.
Materials that are closely related to regenerated cellulose are not, in fact, regenerated cellulose themselves but rather esters of cellulose. These cellulose derivatives share similarities with regenerated cellulose but possess distinct chemical structures and properties.
Nitrocellulose is a cellulose derivative that is soluble in organic solvents. Its primary applications include being utilized as an explosive or as a lacquer. Notably, many early plastics, such as celluloid, were manufactured from nitrocellulose due to its unique properties and versatility.
Cellulose acetate bears many similarities to viscose rayon and was once regarded as the same textile. However, there are key differences between the two materials.
While rayon is heat-resistant, acetate is susceptible to melting. Special care must be taken when laundering acetate, either through hand-washing or dry cleaning, as acetate garments can disintegrate when exposed to heat in a tumble dryer.
Nowadays, it is mandatory to distinguish between the two fabrics on garment labels, ensuring consumers are aware of the specific material used.
Cellophane is typically produced using the viscose process, similar to rayon. However, instead of being formed into fibres, the material is dried into thin, transparent sheets, resulting in its distinctive appearance and properties.
Rayon’s major properties
Rayon is a versatile fibre, often praised for possessing comfort properties similar to those of natural fibres. Its drape and slipperiness can resemble nylon, while its texture can mimic silk, wool, cotton, and linen. Easily dyed in various colours, rayon fibres boast softness, smoothness, coolness, and high absorbency. While rayon may not consistently insulate body heat, its cool and sometimes slightly slimy feel makes it ideal for hot and humid climates.
Regular viscose rayons have low durability and appearance retention, particularly when wet, and exhibit the least elastic recovery of all fibres. However, high-wet-modulus (HWM) rayon is significantly stronger and offers improved durability and appearance retention. Dry cleaning is recommended for regular viscose rayon, while HWM rayon can be machine-washed.
Characterized by lengthwise striations and an indented circular cross-section, regular rayon differs from HWM and cupra rayon, which have rounder cross-sections. Filament rayon yarns range from 80 to 980 filaments per yarn and 40 to 5,000 denier in size. Staple fibres, measuring 1.5 to 15 denier, are mechanically or chemically crimped.
Although rayon fibres are naturally very bright, adding delustering pigments reduces this inherent brightness.
Tracing the History of Rayon Fabrics
Hilaire de Chardonnet, a French scientist and industrialist, invented the first artificial textile fibre, artificial silk, which led to the creation of viscose. Edward John Bevan and Charles Frederick Cross, two British scientists, patented their cellulose-dissolving process in 1892. They later formed the Viscose Syndicate and the British Viscoid Co. Ltd. to commercialize the process.
Research from the 1930s revealed that 30% of American rayon workers experienced severe health effects due to carbon disulfide exposure. Courtaulds, however, made efforts to keep this information from being published in Britain.
During World War II, Nazi Germany forced political prisoners to work under horrific conditions at the Phrix rayon factory in Krefeld. It used forced labour for rayon production across occupied Europe.
In the 1990s, viscose rayon manufacturers faced lawsuits over negligent environmental pollution. Emissions abatement technologies, such as carbon-bed recovery, were not consistently applied across the industry. Pollution control and worker safety eventually became limiting factors in production costs.
While Japan has reduced carbon disulfide emissions per kilogram of viscose rayon produced by around 16% per year, other rayon-producing countries, including China, have uncontrolled emissions. Rayon production has remained steady or decreased, except in China, where it continues to grow as of 2004.
Rayon production has largely shifted to developing countries like China, Indonesia, and India. Disability rates in these factories remain unknown as of 2016, and concerns for worker safety persist.
Lyocell as a Sustainable Alternative to Viscose
Environmental concerns drive the development of lyocell
Environmental concerns drove the development of lyocell. Researchers sought a less harmful manufacturing process for rayon compared to the viscose method.
The lyocell process was developed in 1972 by a team at the now-defunct American Enka fibres facility in Enka, North Carolina. In 2003, Neal E. Franks received the Henry E. Millson Award for Invention from the American Association of Textile Chemists and Colorists (AATCC) for lyocell. Between 1966 and 1968, D. L. Johnson of Eastman Kodak Inc. studied NMMO solutions. From 1969 to 1979, American Enka tried unsuccessfully to commercialize the process.
Mcorsley first detailed the fundamental process of dissolving cellulose in NMMO in a 1981 patent for Akzona Incorporated. During the 1980s, Akzo licensed the patent to Courtaulds and Lenzing.
Commercialization and expansion of lyocell production
Courtaulds Fibres developed the fibre under the brand name “Tencel” in the 1980s. In 1982, a pilot plant was built in Coventry, UK, and production increased in 1984. In 1988, a semi-commercial production line opened at the Grimsby, UK, pilot plant.
The process was first commercialized at Courtaulds’ rayon factories in Mobile, Alabama (1990) and Grimsby (1998). By 1993, the Mobile Tencel plant reached full production levels of 20,000 tons per year. By 2004, production had quadrupled to 80,000 tons.
Lenzing began a pilot plant in 1990 and commercial production in 1997. In 2004, Lenzing was producing 40,000 tons. In 1998, Lenzing and Courtaulds resolved a patent dispute.
Merger and acquisition in the lyocell industry
In 1998, Akzo Nobel acquired Courtaulds and merged the Tencel division with other fibre divisions under the Accordis brand. Subsequently, CVC Partners purchased these divisions from Akzo Nobel. In 2000, Lenzig AG acquired the Tencel division from CVC, and merged it with their “Lenzing Lyocell” business, retaining the Tencel brand name. By 2015, Lenzing AG had become the largest lyocell producer, boasting an annual production of 130,000 tonnes.
As of 2018, the lyocell process is not so widely used as it remains more expensive than the viscose process.
Questions of sustainability
Rayon’s manufacturing process
Rayon production can indeed have negative environmental impacts. Sourcing cellulose from rainforests contributes to deforestation and habitat destruction, particularly in regions like Sumatra and Indonesia. The production process can also be harmful to workers, local populations, and water sources due to the use of toxic chemicals.
While some companies, like Lenzing, have developed more eco-friendly alternatives such as modal rayon, it is essential to consider the overall environmental cost. The large-scale harvesting of softwood trees for cellulose production still contributes to deforestation and resource depletion, despite the fabric’s biodegradability.
As a consumer, it’s important to be aware of the environmental and ethical implications of the products you purchase. When possible, choose clothing and textiles made from more sustainable, eco-friendly materials or from companies that implement environmentally responsible practices in their production processes. By supporting sustainable practices, you can contribute to reducing the negative impacts of rayon production on the environment and communities.
Rayon’s disposal and biodegradability
The biodegradability of different fibres has been studied. Rayon is more biodegradable than cotton, which in turn, is more biodegradable than acetate. However, some factors, such as water repellency, can affect the decomposition rate. It is also worth noting that some insects, like silverfish, can consume rayon, but the damage caused is typically minimal.
In marine environments, research has shown that rayon contributes significantly to the total fibres found in deep ocean areas. A 2014 survey found that rayon accounted for 56.9% of fibres in deep ocean areas. A 2016 study found that cotton was the most frequent match (50%), followed by other cellulosic fibres at 29.5%, which includes rayon/viscose and other natural fibres. However, it is challenging to distinguish between natural and man-made cellulosic fibres using methods like Fourier transform infrared spectroscopy, which can lead to discrepancies in the data.
This information highlights the importance of considering the environmental impact of various fibres and materials used in textile production. As consumers, we can make a difference by choosing products made from sustainable, eco-friendly materials or supporting companies that follow environmentally responsible practices.
The concerns about links between rayon manufacturers and deforestation have indeed led to collaborations between organizations like the Forest Stewardship Council (FSC), the Programme for the Endorsement of Forest Certification (PEFC), and CanopyPlanet to address these issues. CanopyPlanet is a non-profit organization that works with the forest industry to protect endangered forests and promote sustainable, eco-friendly practices.
To increase transparency and awareness about the environmental impact of man-made cellulosic fibre production, CanopyPlanet publishes a yearly Hot Button report that ranks and scores manufacturers globally based on their commitment to responsible sourcing, sustainable production, and efforts to mitigate deforestation. The report uses a 35-point scale to evaluate manufacturers.
In the 2020 Hot Button report, Birla Cellulose scored the highest with 33 points, followed by Lenzing with 30.5 points. These scores reflect the companies’ commitment to sustainability and responsible sourcing of raw materials. By evaluating and ranking manufacturers, the Hot Button report aims to encourage improvements in the industry. It helps consumers make more informed choices when it comes to purchasing products made from these fibres.
Who are the key manufacturers of Rayon?
In 2018, the global production of viscose fibre was approximately 5.8 million tons. China was the largest producer, accounting for about 65% of the total production. Various trade names are used in the rayon industry to label different types of rayon in products.
Bemberg, a trade name for cuprammonium rayon, was developed by J. P. Bemberg. It has a smaller diameter and is closer to silk in feel than viscose rayon. Currently, Bemberg is only produced in Japan and has finer fibres than viscose rayon.
Lenzing AG manufactures popular rayon forms, including Modal and Tencel. Tencel, also recognized as lyocell, undergoes a unique solvent recovery process and is deemed a separate fibre by the US FTC. Courtaulds Research at the Grimsby plant in England initially produced Tencel lyocell commercially, having developed the process to dissolve cellulose without triggering a chemical reaction.
Birla Cellulose is another major manufacturer of rayon with plants in India, Indonesia, and China. Accordis was a significant producer of cellulose-based fibres and yarns, with production facilities across Europe, the US, and Brazil.
Visil rayon and HOPE FR are flame-retardant forms of viscose that incorporate silica into the fibre during manufacturing.
The North American Rayon Corporation in Tennessee was a producer of viscose rayon until it closed in 2000.
Indonesia is among the world’s largest rayon producers. With Asia Pacific Rayon (APR) they have an annual production capacity of 0.24 million tons. This highlights the global distribution of rayon production and the wide range of trade names and types used within the industry.