Lyocell Fiber: Properties, Production and Uses

What is Lyocell Fiber?

Lyocell fiber is a type of regenerated cellulose fiber made from wood pulp.  It is the first in a new generation of cellulosic fibers made by a solvent spinning process. Lyocell’s softness, strength, and moisture management make it a popular choice in modern textile applications. Lyocell was developed as an environmentally friendly, regenerated cellulosic because it uses fewer harmful chemicals; the non-toxic chemical of amine oxide whereas viscose uses caustic soda. Lyocell was commercialized under the trade name of Tencel by Courtaulds in 1994. The lyocell manufacturing process results in recycling approximately 99% of the amine oxide and during production the textile manufacturer produces less smoke emissions and waste water than other manmade fibers. Products made from lyocell can be recycled, incinerated, put into landfill as they biodegrade or can be digested without harming the environment. In the case of digestion, anaerobic digestion allows the fiber to degrade within eight days, leaving water and carbon dioxide which are used to create energy within sewage systems. Lyocell is produced mainly in the United States, Austria, United Kingdom and India. Lyocell is often sold under the trade name Tencel.

Properties of Lyocell Fiber

Lyocell fiber is similar to viscose rayon fiber in many physical aspects, but exhibits enhanced properties in terms of softness, drapability, dimensional stability, dye uptake, and colorfastness. Moisture regain of lyocell fiber is around 11%, slightly lower than that of viscose rayon. This is mainly because the lyocell spinning process produces a higher cellulose crystallinity.

1. Absorbency: Lyocell is highly absorbent due to the fibrils in the structure of the fiber, which are hydrophilic. Moisture wicks to the surface, making it breathable. Its high absorbency allows for a successful dyeing process using reactive, direct or vat dyes.
2. Strength: Lyocell is the strongest cellulosic fiber – it’s even stronger than cotton and linen. Further, it gains strength when it becomes wet.
3. Draping: It has a soft handle to produce a flattering drape.
4. Durability: It has good durability, but care must be taken when rubbing its surface because tiny hairs may rise to the surface.
5. Launder: It is easy care launder using low temperature wash cycles, and has minimal shrinkage.
6. Resiliency: Lyocell is fairly resilient, which means creases will disappear, especially if the fabric is hung in a warm, damp place e.g. bathrooms. Generally, chlorine bleaches will not affect fabrics made out of lyocell.
7. Susceptible: Lyocell pills and fibrillates easily. During wet processes the fibrils, hairs on the surface of the fiber, peel away causing pilling; however, this can be used to the fiber’s advantage when used in calendering for a peach effect fabric. Some of the wet processes may be harmful to the environment due to the waste in dyes and chemicals used in the finishing process. Still, the use of amine oxide and its ability to be recycled makes lyocell an eco-friendly fiber. It is, however, susceptible to mildew and damage from silverfish.
8. Sustainable: The use of renewable woodchips in managed reforestation, the non-toxic amine oxide used in the manufacturing process and its ability to be recycled makes lyocell a very sustainable fiber. As it is a cellulose-based fiber, it biodegrades; this property will be used to its advantage in industry such as sewage works. During the production the textile manufacturer produces less smoke emissions and waste water than other man-made fibers.

Finishes of Lyocell Fiber

• Water Resistance on gabardine fabrics for coats.
• Bio-stoning on denims.
• Bio-polishing removes the hairy surface.
• Calendering can be applied for peach and suede effect fabrics.
• Napping makes the material softer and warmer.

Variations of Lyocell Fiber

1. Hollow: Adding sodium carbonate to the solution causes carbon dioxide to form inside the fiber in the coagulating bath, which forms a hollow area inside the fiber. This variation provides better bulk and absorbency; it is known as highabsorbency lyocell and is used for sanitary wear
2. Ribbon: Flat, cross-sectioned shaped fiber creates a textured fabric (similar to woven straw).
3. High-Tenacity: Establishing a thicker skin and aligning the molecules via high extension or stretch produces high tenacity. This variation is used for car tyres.
4. Crimped/Looped: Variations to the coagulating bath can cause latent crimp effects (crimps produced later in the finishing process, when the material is submersed in cold water).
5. Delustre: Varies from bright to semi-dull to dull depending upon the amount of Delustre agent used.

Lyocell Fabrics

Lyocell has all of the benefits of being a cellulosic fiber; it is absorbent with an excellent handle and drape. Lyocell has high wet strength (whereas viscose rayon does not); therefore, it is possible to produce finer yarns and fabrics from lyocell. Lyocell fabrics are breathable, with good moisture absorbency and high dimensional stability.

A large proportion of man-made fabrics on the market today are sold with just the fiber content. However, there are a few fabrics that are either 100% or some percentage of lyocell.

Chambray, chino, corduroy, denim, felt, gabardine, jersey, velvet and velour.

Lyocell blends with Tactel for durability, wind-resistance and water-resistance whilst the Lyocell provides warmth, absorbency and comfort. Lyocell can also be blended with wool, Lycra, cotton, linen, silk and viscose.

Production of Lyocell

Lyocell is a man-made cellulosic fiber, which is produced by regenerating the fiber from a cellulose solution in an organic solvent of N-methylmorpholine-N-oxide (NMMO). Manufacturing of lyocell takes 3 hours (whereas it takes 40 hours to make viscose rayon staple fibers) and requires less energy and water. Lyocell is manufactured from wood pulp. First, it is dissolved at 90–120°C under normal pressure with the solvent NMMO; later, it can be converted into a viscose solution. Then it can be filtered to remove unwanted impurities and extruded through fine jets in a water bath. During the water bath, the solidification process can take place and the polymer gets regenerated (only cellulose). After fiber formation, it should be washed thoroughly and dried. The used solvent can be purified and concentrated for further use; 99.5% of the solvent is recoverable and reusable for processing of further batches. The raw materials are free from environmental problems because they come from managed forest with far less land pollution in comparison with cotton, since there is no utilization of synthetic fertilizers, pesticides, herbicides, or insecticides.

Production flowchart of Lyocell:

Wood pulp from hardwood trees from managed tree farms is washed in water, dried, pressed, and rolled into sheets of cellulose. Each roll weighs approximately 227 kg.

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The rolls are broken into 3-cm squares and placed into heated, pressurized containers filled with amine oxide. This process dissolves the cellulose.

➡Approximately 99% of amine oxide is recycled.

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The clear solution is filtered to remove all impurities.

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Wet Spun: The solution is pumped through a spinneret and extruded through a bath of dilute amine oxide, which sets the fibers.

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The fibers are washed in demineralized water.

➡The amine oxide solution is purified.
⬆The water is evaporated.

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The fibers are dried to evaporate the water, then put into either soap or silicone to lubricate the fibers.

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1. Staple fibers are created.
2. Continuous filament is created.

Toxicological Aspects of Lyocell

After manufacturing, 99.5% of the NMMO is recycled and used for further batches. Very small quantities of NMMO are discharged into wastewater and can be degraded with proper biological treatment. Other chemicals used during manufacturing do not create any environmental issues. Eleven grams of COD is produced for production of 1 kg of fiber.

Uses of Lyocell Fiber

Due to its exceptional properties, Lyocell is used in a wide range of products, often alone or blended with other fibers like cotton, polyester, or wool. Lyocell is used in the manufacture of the following products:

• Fibers
• Nonwoven textiles
• Conveyor belts
• Specialty papers
• Medical dressings
• Surgical swabs, drapes, gowns
• Floppy disk liners, filtration cloths
• Lining materials

Typical uses of lyocell fiber are:
Women’s fashion garments, such as dresses and blouses; men’s shirts, jeans, coats and protective clothing. Also used for soft furnishings, including towels, pillowcases, sheets and curtains. Used in the industrial world to make conveyor belts, filters in low-tar cigarettes, filters, wet wipes, medical dressings, tea bags, maps and envelopes.

Conclusion

Lyocell fiber represents the future of sustainable textile materials. It is a strong, soft, and highly absorbent regenerated cellulose fiber. Produced from wood pulp using an eco-friendly, closed-loop solvent spinning process (NMMO), it is biodegradable and sustainable. Its versatility makes it ideal for apparel, home textiles, and specialized industrial uses.

References

[1] Ashford, B. (2016). Fibers to Fabrics.

[2] Venkatesan, H., Periyasamy, A.P. (2019). Eco-fibers in the Textile Industry. In: Martínez, L., Kharissova, O., Kharisov, B. (eds) Handbook of Ecomaterials. Springer, Cham. https://doi.org/10.1007/978-3-319-68255-6_25

[3] Veit, D. (2023). Fibers: History, Production, Properties, Market. Springer Nature.

[4] Sinclair, R. (2014). Textiles and fashion: Materials, Design and Technology. Woodhead Pub Limited.

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