Material Series IX : Cheeky Cellulose
Updated: Jan 29, 2020
After having received a couple of questions from friends about Viscose, I realized this was an important one still missing from the material series. So here it is.
I must admit that researching for this blog wasn’t as easy as I expected. Compared to the other materials we have discussed, there is a lot more chemistry that comes into play for these materials and understanding the differences wasn’t very straight forward so I will do my best to explain clearly.
Cellulose fibres is a collective name for fibres made with compounds of cellulose, which can be obtained from the bark, wood or leaves of trees and plants, or from other plant-based material.
There is a difference between natural cellulose fibres and manufactured cellulose fibres. With natural cellulose fibres, you can still recognize they are part of the original plant because they are only processed as much as needed to clean the fibres for use: cotton fibres look like the soft fluffy cotton balls that they come from and linen fibres look like the strong fibrous strands of the flax plant.
Manufactured cellulose fibres come from plants that are processed into a pulp and then extruded in the same ways that synthetic fibres like polyester or nylon are made.
Rayon or viscose is one of the most common "manufactured" cellulose fibres, and it can be made from wood pulp.
Rayon is a manufactured fibre made from regenerated cellulose fibre. The many types and grades of rayon can imitate the feel and texture of natural fibres such as silk, wool, cotton, and linen. The types that resemble silk are often called artificial silk.
Rayon is made from purified cellulose, primarily from wood pulp, which is chemically converted into a soluble compound. It is then dissolved and forced through a spinneret to produce filaments which are chemically solidified, resulting in fibres of nearly pure cellulose.
Because rayon is manufactured from naturally occurring polymers, it is considered a semisynthetic fibre, whereas in precise usage the term synthetic fibre is sometimes reserved for fully synthetic fibres. Specific types of rayon include viscose, modal and lyocell, each of which differs in the manufacturing process and properties of the finished product.
Viscose is often promoted as a sustainable alternative to cotton or polyester and is popular in the fashion industry as a cheaper and more durable alternative to silk. It’s usually what’s used to create those drapey summer dresses, skirts, soft blouses, and synthetic velvet. But viscose isn’t just found in our clothes — it’s also used in the manufacturing of upholstery, bedding, carpets, cellophane and even sausage casing!
Viscose Rayon has a truly European story. French scientist and industrialist Hilaire de Chardonnet (1839-1924) is credited with inventing the first commercial viscose fibre, as a cheaper alternative to silk. But the fabric was so flammable it was quickly taken off the market until a safer process was developed by the German Bemberg Company. In 1892, British scientists Charles Frederick Cross, Edward John Bevan and Clayton Beadle discovered and patented the production process, and by 1905 the first commercial viscose rayon was on the market. It was produced by the U.K. company Courtaulds Fibres in 1905. Courtaulds formed an American division, American Viscose, (later known as Avtex Fibers) to produce their formulation in the United States in 1910. The name "rayon" was adopted in 1924, with "viscose" being used for the viscous organic liquid used to make both rayon and cellophane. In Europe, though, the fabric itself became known as "viscose", which has been ruled an acceptable alternative term for rayon by the U.S. Federal Trade Commission (FTC).
The viscose method can use wood as a source of cellulose, whereas other types of rayon require lignin-free cellulose as starting material. The use of woody sources of cellulose makes viscose cheaper, so it was used on a larger scale than the other methods. On the other hand, the viscose process affords large amounts of contaminated wastewater.
Modal fibre is the generic name for a semi-synthetic rayon, which was originally developed in Japan in 1951. Today one of the best-known producers of modal is the Austrian company Lenzing AG, who market their version under the name Lenzing Modal®. Lenzing Modal is protected by a global certification system which is registered worldwide.
With the rise in popularity of fashionable activewear, this soft and stretchy fabric is more in demand than ever. It motivated manufacturers to produce various forms of Modal to suit demand.
Modal and viscose are made using a very similar process with similar chemicals used at each stage of production. Viscose production has been continuously refined over the past 100 years to make a textile which is soft yet easy-care. However, modal fibres are treated slightly differently after spinning to make the filaments stronger. For example, the fibres are also stretched to increase molecular alignment. This means that modal fibres have the potential to be lighter and finer and can be tumble dried without damage. Other than that viscose and modal are similar products.
Modal is breathable and silky smooth to the touch, it is around 50% more water-absorbent per unit volume than cotton. Boasting similar properties to other cellulose fibres, it’s designed to absorb the dye and stay colour-fast when washed in warm water, making it a popular choice in the manufacture of underwear and activewear alike.
With an impressive resistance to shrinkage and pilling, it’s worth noting that modal may be used on its own or in a textile blend.
Tencel ~ Lyocell
Tencel is increasingly the fabric of choice for ethical and conscious clothing brands. It’s light and versatile and is widely used in casual wear.
Lyocell is still the same plant-based fibre as viscose and modal, but it is made using a slightly different process. Lyocell production uses a different solvent to extract the cellulose from the wood: sodium hydroxide (caustic soda) is replaced by a non-toxic organic compound with the catchy name N-Methylmorpholine N-oxide (NMMO for short). This organic solvent is easier to filter and re-use in a closed loop, which is better for the environment. The Austrian firm Lenzing go a step further by only making their lyocell, branded as TENCEL®, from fast-growing Eucalyptus trees from sustainably managed forests.
Pros & Cons
Rayon is a versatile fibre and is widely claimed to have the same comfort properties as natural fibres. It can imitate the feel and texture of silk, wool, cotton and linen. The fibres are easily dyed in a wide range of colours. Rayon fabrics are soft, smooth, cool, comfortable, and highly absorbent, but they do not insulate body heat, making them ideal for use in hot and humid climates, although also making them feel “fresh” hence they are perfect for sportswear.
The durability and appearance retention of regular viscose rayon are low, especially when wet; also, rayon has the lowest elastic recovery of any fibre.
Since rayon’s base is plant materials, it is biodegradable. However, concerns have also been raised regarding the devastating impact of wood pulp production on forests, people and vulnerable animal populations.
The production of viscose is contributing to the rapid depletion of the world’s forests, which are being cleared to make way for pulpwood plantations. It is estimated that around 30% of rayon and viscose used in fashion is made from pulp sourced from endangered and ancient forests. This leads not only to habitat destruction, creating a significant threat to endangered species, but also often involves human rights abuses and land grabbing from Indigenous communities.
An article in the Guardian detailed an investigation undertaken by the Changing Markets Foundation that linked international fashion brands such as Zara, H&M and ASOS to highly polluting viscose factories in China, India and Indonesia.
Though the viscose production process is multi-faceted, retailers play a significant role in the problem. Fast-fashion giants are placing pressure on manufacturers to produce and distribute clothes at ever-increasing speeds and cheaper costs. This encourages these unsustainable social and environmental practices. Big brands have the money and power to step up and encourage responsible and sustainable manufacturing, but we are yet to see enough meaningful action.
Lenzing has developed innovative environmental processes for the manufacture of Lenzing Modal which are not commercially available to others. These non-toxic technologies have allowed Lenzing to recover up to 95% of Modal’s production materials, minimising emissions and conserving resources.
The environmental footprint of Lenzing Modal is a positive one – it’s carbon-neutral, requires less land per tonne than cotton fibres and has a water consumption level that’s 10 to 20 times less than that of cotton. Many brands, therefore, see Modal as an eco-friendly choice.
So what are the challenges regarding Modal? Whilst the trademarked Lenzing Modal is harvested from sustainably managed beech tree plantations in Austria and surrounding European countries, the origins of other modal fibres on the market are often less transparent. For example, less reputable manufacturers have been accused by the Rainforest Action Network of forest destruction in Indonesia. According to sustainable fashion commentator Summer Edwards, “modal that has been produced in Indonesia is known to be manufactured with plantation wood stock that is grown in areas of rainforest that have been clear-felled to make way for monocrop timber plantations”. Modal garments manufactured in China are often made with Indonesian modal.
A key factor in all of this is that Lenzing does not produce ready-to-wear fabrics. Instead, the company sells yarns to mills and manufacturers who in turn make fabrics. The environmental impact involved in weaving fibres into fabrics can be significant, with conventional methods using high levels of water and chemicals.
Tencel manufacturing requires less energy and water than cotton. Lenzing says it sources its wood and pulp from certified and controlled sources like sustainably managed plantations.
The solvents used to turn the wood pulp into fibre are made using petrochemicals. However, the closed loop production process means that the solvent is recycled time and time again to produce new fibres and minimise harmful waste. Lenzing Group says the solvent recovery rate is 99%.
Although it is mixed with conventional dyes, which can be harmful to the environment, lyocell requires a lot less dye than cotton. Lenzing AG was presented with a European Award for the Environment from the European Union for developing this process, called REFIBRA™ technology.
Addition 24/4/2019: After having spoken to a Lenzing representative, I now have a better understanding of the Refibra techonology: it uses about 30% pre-consumer (post-industrial) cotton waste to create pulp, this is then introduced into the lyocell process mixing wood pulp and recycled cotton pulp together to create new fibers and yarns.
The main concern with Tencel fabric is the use of energy during the production process. This is something that Lenzing AG have acknowledged and are working to address by increasing their use of renewable energy sources.
It is important to consider both the fibre and the weaving, cutting and transportation process when thinking about the sustainability of a fabric. Be sure to choose brands with transparent production processes to make sure you’re making the most ethical choice.
Better alternatives: EcoVero (Lenzing), Naia (Eastman)
As technology progresses, new materials are created, such as EcoVero. Produced by Lenzing, this innovative fabric is made using sustainable wood from controlled sources which are either Forest Stewardship Council or Program for Endorsement of Forest Certification Schemes certified in Europe,
instead of bamboo or eucalyptus. More than 60% of the trees used to produce the fibre come from Austria and Bavaria to ensure lower emissions. Nearly all the chemicals used during the production of EcoVero are also recovered and reused, causing 50% fewer emissions and taking up half as much energy and water. Armedangels started using EcoVero in 2017, such as in this cool and trendy dress.
Naia prides itself on full transparency from tree to yarn, Naia is responsibly sourced from sustainably managed pine and eucalyptus plantations, ensuring no deforestation. Eastman holds FSC® and PEFC™ Chain of Custody certification, and all wood pulp suppliers have FSC® and/or PEFC™ Chain of Custody as well.
Naia cellulosic yarn is produced in a safe, closed-loop process where solvents are recycled back into the system for reuse. Naia is OEKO-TEX® 100 Product Class I certified and is made with no hazardous chemicals listed on the ZDHC Manufacturing Restricted Substances List.
Naia has an optimized, low-impact manufacturing process with a low tree-to-yarn carbon and water footprint. Naia has a third-party reviewed life cycle assessment compliant with ISO 14044 and is ranked on the Higg Materials Sustainability Index.
All the certificates are available on their website.
What else can we do?
Choose natural fabrics — Purchase garments made from natural, organic, sustainable or recycled fibres, such as organic cotton, hemp, linen and natural dyes. Keep in mind that some natural materials such as cotton and wool have their own ethical issues regarding environmental sustainability, labour rights and animal welfare.
Buy less, buy second-hand — Choosing well and buying less is a great way to reduce your impact on the environment. When you do want to add to your wardrobe, buying second-hand is a great way to form your own unique style! And it’s also fantastic for the environment and your bank account! Get informed — Looking to buy something brand new? Look for brands that care about their environmental impact, the rights of their workers and animal welfare. The Good On You app is a great tool for finding brands that share your values.
This post turned into a long one however I felt it was important to give you the full picture. I hope you have a bit more clarity on this rather complicated world of cellulose fabrics.