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.
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*Microfiber Update
by Editor Wendy Priesnitz
Every time you
wash synthetic fabrics, millions of microfibers are released into the
water. Microfibers are too small to be filtered out by waste treatment
plants, so they end up in our waterways and oceans, where they wreak
havoc on marine animals and the environment.
Plastic fibers are now showing up in fish and shellfish
sold in in California and Indonesia for human consumption. In fact, microfibers are responsible for over eighty percent of shoreline pollution
across the globe.
Learn more about microfiber pollution here.
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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.
