Eco-Fiber or Fraud?
Are Rayon, Modal, and Tencel Environmental Friends or Foes?
by Ed Mass 

Most everyone is familiar with rayon. Fewer people are familiar with modal and lyocell. All three are called “cellulosic fibers,” since the natural material that makes up the fiber is cellulose, a component of all plants. The cellulose is often derived from wood pulp, which has an average cellulose content of forty percent, and sometimes from bamboo. Hence, these fibers are often referred to (and sometimes marketed as) "environmentally friendly."

Before answering the question in the title of this article, I’ll explain these fibers and their properties. I will also refer to the practices of one company – Lenzing AG of Germany – an innovative leader in fiber development and environmental protection. Lenzing manufactures more cellulosic fiber from trees than any other company in the world and has been producing rayon/viscose, the first generation cellulose fiber, since 1938.

Three Generations of Technology

Rayon is known by the names viscose rayon and art silk (abbreviated from “artificial silk”) in the textile industry. It usually has a high luster quality, giving it a bright shine. Modal is the second generation and is known for its softness. Lyocell is third generation technology. Its advantages include the environmental friendliness of its processing combined with its softness, drape and anti-bacterial properties. You may be familiar with the term Tencel®, which is Lenzing’s brand name for lyocell.

Although they are manufactured fibers, rayon, modal and lyocell are not considered synthetic. All three are referred to generically as “regenerated cellulosic fibers” due to the manner in which they’re manufactured. Nor are they natural fibers produced directly from plants or animals. However, their properties and characteristics are more similar to those of natural cellulosic fibers, such as cotton, flax (linen), hemp and jute, than those of petroleum-based synthetic fibers such as nylon or polyester.

They may be called “semi-synthetic fibers” to reflect the combination of the natural raw cellulosic material and the chemical manufacturing process that breaks down the cellulose so it can be “regenerated” into a fiber from the original pulp.

Rayon

Rayon is a very versatile fiber with a wide array of applications. It has the same comfort properties as natural fibers and is easily dyed in a wide range of colors. Rayon is breathable and does not insulate body heat, making it ideal for use in clothing worn in hot and humid climates. Rayon is more moisture absorbent than cotton and does not build up static electricity; nor will it pill unless the fabric is made from short, low-twist yarns. It is comfortable, soft to the skin and has moderate dry strength and abrasion resistance. Like other cellulosic fibers, it is not resilient, which means that it will wrinkle. Rayon withstands ironing temperatures slightly less than those of cotton. It may be attacked by silverfish and termites, but generally resists insect damage.

Rayon was the first manufactured (regenerated) fiber, dating back to about 1855. The first patent for “artificial silk” was registered in 1894, the first U.S. commercial production occurred in 1910 and the term rayon was officially adopted in 1924.

There are many different processes for manufacturing rayon, varying among the chemicals used and their subsequent impact on the environment. Basically, the production of rayon (which also applies to modal and lyocell) chemically converts purified cellulose into a soluble compound. The solution is passed through a spinneret (similar to the holes in a showerhead) to form soft filaments that are then converted or “regenerated” into almost pure cellulose.

Much of the commercial rayon manufacturing utilizes the “viscose” process, in which the purified cellulose is converted to xanthate, the xanthate dissolved in dilute caustic soda and the cellulose regenerated from the product as it emerges from the spinneret.

Rayon fabrics have different strength and stretch characteristics created by adjusting the drawing process applied in spinning. “Regular rayon” has the largest market share. Typically found in apparel and home furnishings, it is identified on labels as “rayon” or “viscose.” Its distinguishing property is its low wet strength. As a result, it becomes unstable and may stretch or shrink when wet. Dry cleaning is usually recommended because untreated regular rayon can shrink as much as ten percent when machine washed. Formaldehyde-free finishes are sometimes applied to make viscose rayon fabrics washable and limit shrinkage to three percent.

Other types of rayon have been developed for specialized end uses. These include high tenacity rayon, which is primarily found in tire cord and industrial end uses, and high-absorption rayon fibers with moisture-holding properties for disposable diapers, hygiene and incontinence pads, as well as medical supplies. One of rayon’s strengths is its versatility and ability to blend easily with many fibers.

Modal

The desire to create a higher wet strength rayon led to the development of modal as the second generation of this cellulosic fiber. Modal is a “high wet modulus” rayon, which has virtually the same properties as regular rayon plus high wet strength and extra softness, making it especially useful for body contact clothing such as lingerie and undergarments. Modal is wear resistant and can be machine washed and tumble dried without shrinking or getting pulled out of shape. It performs much like cotton and can be mercerized for increased strength and luster.

Modal is about fifty percent more water-absorbent per unit volume than cotton. It’s designed to dye just like cotton and is color-fast when washed in warm water. Textiles made from modal are resistant to shrinkage, fading and graying. Modal fibers have found a wide variety of uses in clothing, outerwear, and household furnishings. They are often blended with cotton, wool or synthetic fibers, and take and retain dyes well.

Modal fibers were developed in Japan in 1951 and Lenzing started selling its version of them in 1964. Lenzing Modal® is made from sustainably harvested beech trees and the company uses an environmentally friendly bleaching method for pulp.

Lyocell

The third generation rayon fabric is lyocell. Lenzing began pilot production of its Tencel® lyocell fiber in 1990, with full operations starting in 1997.

Lyocell has numerous advantages over rayon and modal in its properties as well as its manufacturing process. One of the major “claims to fame” of lyocell is its ability to absorb excess liquid (perspiration) – at a rate of fifty percent more than cotton – and quickly release it into the atmosphere. In doing so, lyocell supports the natural ability of the skin to act as a protective shell to regulate body temperature and maintain water balance. At the same time, lyocell’s moisture management does not give bacteria a chance to grow. Moisture is directly absorbed from the skin and transported to the inside of the fiber, rather on the surface where bacteria could grow.

As a result, clothing made of lyocell remains odor-free for multiple wearings and much longer than cotton. This means fewer washings and saving on water and energy as well as on the wear and tear that occurs on any fabric from the washing and drying processes. By contrast, synthetics have hundreds to thousands of times higher bacteria count over the same time periods as lyocell. Even better, lyocell’s anti-bacterial property is inherent to the fiber without the chemical additives that are used on synthetics and many cotton products.

Nanofibrils are the key to the performance of lyocell, which is the first cellulose fiber to use this nanotechnology. The nanofibrils are hydrophilic (meaning they have a strong attraction to absorbing water) and optimize absorption of moisture with excellent cooling properties. By contrast, synthetic fibers do not absorb moisture.

Lyocell fibers are also gentle on the skin. The microscopic surfaces of lyocell fibers, due to the nanofibrils, are smoother than the surfaces of modal, cotton and wool, reducing skin irritation. It is the combination of this extremely smooth surface of lyocell and excellent moisture absorption that makes lyocell textiles feel so soft and pleasant to the skin, making them ideal for active wear, clothing for sensitive skin and home textiles such as bedding. In addition, lyocell is hypoallergenic and anti-static and fabric made from it doesn’t cling.

Lyocell manufacturing is extremely flexible. Manipulating or controlling the fibrils, the very fine hairs found on the outer fibers, produces a wide variety of fabrications, from rugged denim to suede-like surfaces to a clean, smooth silky touch. As with silk, this fibrillation is responsible for the pleasant and soft hand of lyocell fabrics.

Lyocell can also be manipulated to create an excellent fill material. When used for bedding, its excellent moisture management and temperature regulation create a pleasant and dry climate during sleeping.

Lyocell fabrics with natural elongation and recovery properties can be created without having to use elastomeric fibers such as spandex. The high tenacity of lyocell in both a wet and dry state increases the dimensional stability of the end product. Therefore, even a small percentage of lyocell combined into other yarns and fabrics increases their durability.

Microfibers* are very fine fibers – less than about one-half the thickness of a fine silk fiber – that can be manufactured from regular rayons, modal and lyocell. [See sidebar for an update by our editor regarding  microfibers.] Fabrics from microfibers are very drapable and silk-like in hand and appearance. Modal can be blended with cotton to vary the characteristics from what each offers alone. Ideally, organic cotton should be used to maintain the environmental benefits of the total product.

Environmental Friends or Foes?

Rayon, modal and lyocell are produced from renewable cellulosic plants such as beech trees, pine trees, and bamboo. All three fibers are biodegradable. Specifically, Lenzing Viscose® and Lenzing Modal® are produced from sustainably harvested beech trees and Tencel® from sustainably harvested eucalyptus trees. Eucalyptus grows quickly and without irrigation, pesticides, fertilizers or genetic manipulation; it can also be planted on marginal land that cannot be used for food crops. The fiber yield per acre from the trees used in the Lenzing fibers is up to ten times higher than that of cotton. Also, cotton needs up to 20 times more water.

However, there are many manufacturers of rayon. Even with the advancements that have been made over time, most rayon manufacturing processes in use today are not considered environmentally friendly. In fact, they use a range of polluting chemicals and heavy metals. On the other hand, lyocell manufacturing, and that of Tencel® in particular, is an extremely environmentally friendly process and the most friendly of these three fibers.

Since regenerated fibers do not qualify for organic certification, other recognized eco standards that review the entire process chain for growing and harvesting the trees through the manufacturing and treatment processes must be applied to these fibers. One such award that has been given to Lenzing for Tencel® is the European Eco-Label, which addresses compliance with high environmental standards for production and products.

As early as 1963, Lenzing started recycling the chemicals from pulp production after the company switched from the calcium bisulphite method to an environmentally friendly magnesium bisulphite method. The revolutionary aspect of Tencel® manufacturing is the recovery and reuse of up to 99.8 percent of the solvent and the remaining emissions are broken down in biological water treatment plants. In fact, the solvent is not acidic, does not remain in the fiber, and has been proven harmless in dermatological and toxicological tests.

Finally, we need to remember that much of the total environmental impact of textile goods comes from their care. With lyocell fabrics, there is no need for fabric softener or whitening agents, and energy and water use can be decreased due to shorter washing machine cycles. So with this knowledge and careful shopping for respected eco-friendly labels, you can buy textiles from manufactured fibers that can be considered to be green.

Ed Mass is President and Founder of Yes It’s Organic, an online store for organic, fair labor, and eco friendly clothing and household goods. After being an environmentalist for over 40 years he decided to participate more directly by educating consumers. This article was first published in 2009.  

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