What is Tencel Lyocell?

Tencel® is the brand name for a recently improved fabric from a fiber generically called lyocell.  Under the “Textile, Wool, and Fur Labeling Acts” of the U.S. Government, man-made and natural fibers must be identified by their generic names.  What this means according to U.S. law is that garment labels that say Tencel^® should actually be labeled as lyocell. When you identify fiber content on a label, or in advertising, you must use the generic fiber name recognized by the Federal Trade Commission. A trademark name alone does not suffice.  Of course, Tencel® is the commonly known name and few actually call the fabric by its generic name lyocell.  We will use the proper generic name lyocell.  Remember that Tencel® is just the brand name for a type of lyocell. 

Lyocell is a natural, man-made fiber produced in an environmentally-friendly process from wood pulp that has become popular in clothing because it is absorbent and comfortable for wear, especially in conditions of high humidity.  Lyocell also drapes attractively and is flattering in dresses and shirts.

Lyocell is stronger than cotton or regular viscose rayon and does not lose strength when wet as viscose rayon does. Lyocell stretches more than cotton, but less than viscose. It is often blended with cotton and/or polyester, mainly in woven fabrics, rather than knits. It is absorbent and comfortable for wear in conditions of high humidity because it is cellulosic which causes moisture to be wicked away from your skin. It is manufactured by a solvent spinning process, but the solvent is recycled so its manufacture is an environmentally friendly process compared to other rayons.

Regarding the production of manufactured fibers, a distinction should be made between cellulosic and non-cellulosic fibers. Four manufactured fibers - rayon, acetate, triacetate and lyocell - are cellulosic fibers. This means that one of the components used in their production is natural cellulose. Cellulose is wood pulp, generally obtained from trees. All of the remaining manufactured fibers are non-cellulosic, which means they are entirely chemically-based.  Cellulose is the natural polymer that makes up the living cells of all vegetation. It is the most abundant and replenishing biopolymer on earth.

What are the properties of lyocell?

Lyocell breathes and washes like cotton, yet has the soft, fluid, natural draping qualities of rayon with a luxurious and refined look.  Lyocell has many qualities and properties that make it an excellent fabric:

·        Comfortable.  It is soft, breathable, lightweight and comfortable with a feel similar to rayon. 

·        Lasting.  It is shrink-resistant, durable and easy to care for.  It is an exceptionally strong fiber when wet or dry.

·        Color rich.  Lyocell fibers are highly absorbent and bind well with dyes.

·        Easy to maintain. Lyocell garments are easy to pack, resist wrinkling and dry quickly. Most are machine washable.

·        Eco-friendly.  Lyocell is made from the natural cellulose found in wood pulp and is biodegradable.

One of the interesting properties of lyocell is its potential to fibrillate. Fibrillation is where the wet fiber, through abrasive action, develops micro-fibrils (or tiny fibers) on its surface. By manipulating or controlling fibrillation, a variety of different fabric finishes may be achieved.  For example, the surface fibers of lyocell are often fibrillated to produce a luxurious, soft-touch fabric with a peach skin surface.  Or, they can be not fibrillated to create a surface finish that has a subtle surface luster with excellent print definition and high tear and burst strength for woven and knitted fabrics.

Lyocell is often blended with other natural fibers such as wool, cotton, silk, flax and various manufactured fibers. When blended with other fibers it gives a wonderful sheen to the yarn and adds softness to many other fibers.  Cotton blended with lyocell becomes stronger and wool/lyocell blends are more absorbent.

Lyocell was created to accept color more readily. It can be dyed from the palest tints through medium tones to vibrant, deep darks. Garments made from lyocell are inherently soft and smooth to the touch. The fabric drapes well in soft, gentle folds. Depending on the finishes applied during manufacturing, lyocell fibers can feel like silk, cotton or wool, and still maintain a washable quality.

How is lyocell made?

Most people assume that there are two general categories of fibers: natural ones, like cotton, wool and silk; and artificial ones synthesized out of petrochemicals like nylon and polyester. Lyocell falls somewhere in-between. The raw material for lyocell is cellulose, which is broken down chemically and reformed as fibers. Lyocell is more accurately described as a recovered or regenerated fiber.

Some have heralded lyocell as a new fiber that represents a milestone in the development of environmentally sustainable textiles.  Lyocell is made from cellulose in wood pulp, which is harvested from tree-farmed trees. Cellulose is the natural polymer that makes up the living cells of all vegetation. The fiber is produced via an advanced 'closed loop' solvent spinning process, with minimal impact on the environment and economical use of energy and water. It uses a non-toxic solvent which is continually recycled during the production process. Production plant emissions into the air, from smokestacks, and water, from wastewater, are significantly lower in comparison to many other man-made fiber operations.

As with conventionally manufactured cotton fabric, there are many steps and processes involved in taking lyocell from fiber to fabric.  The major steps are:

1. Creating a solvent solution from wood pulp

2. Spinning lyocell fiber from the solvent solution

3. Washing lyocell fiber to remove solvents

4. Drying fiber and producing yarns

5. Finishing to produce lyocell fabric

Let’s examine each step more closely for the chemicals and processes used to determine how ecological lyocell is.

Step 1. Creating a solvent solution from wood pulp.

The cellulosic fibers (rayon, acetate, triacetate and lyocell) come from purified wood pulp, which first must be shredded and then dissolved.  The manufacturing process for lyocell is based on the principle of direct solvent spinning. In contrast to common production processes, the cellulose in wood pulp does not need any prior chemical modification ("derivatization"), but it dissolves in a purely physical manner, just like sugar in water.  The manufacturing process is characterized by almost completely closed solvent and water cycles. This reduces emissions significantly.

The wood pulp solution is produced in a straight solvation process by dissolving wood pulp at high temperatures and pressure in a non-toxic organic solvent solution of amine oxide, particularly N-methylmorpholine N-oxide, which is reclaimed and recycled in a “closed loop” spinning process conserving energy and water.  Up to 99% of the solvent is recovered and reused.  The wood pulp can come from a variety of sources, such as wood chips or even large rolls of paper that have been finely shredded, depending upon the manufacturer’s technologies.

Amine oxide is an amphoteric surfactant widely used in cleaning and personal care products, usually in conjunction with other surfactants.  “Surfactants” is a scientific name for surface-active soaps and cleaners.  The major uses are in laundry and cleaning products, where it functions as a foam stabilizer, thickener and emollient, emulsifying and conditioning agent. Amine oxide biodegrades readily and completely under aerobic and anaerobic conditions and can be highly removed by conventional sewage treatment. The acute toxicity varies between 1.7 and 5.3 ppm and the chronic toxicity between 160 and 1100 ug/L.  Amine oxides have been used in shampoo, bubble bath, and hand-soap formulations in conjunction with alkyl sulfates and olefin sulfonates. 

Step 2.  Spinning lyocell fiber from the solvent solution

Before being formed into fibers, the fiber-producing substance for all manufactured fibers is in a thick liquid state. In the spinning process this liquid is forced through a spinneret, which resembles a large shower head.  “Spinneretes” is the same term used for the silk-producing organs on spiders and caterpillars and their precise design and manufacture is critical to the successful formation of filaments.

A spinneret can have from one to literally hundreds of tiny, finely machined holes in a steel plate. The size of the holes varies according to the size and type of the fiber being produced.  These holes are called Unlike natural fibers, manufactured fibers can be extruded in different thicknesses. This is called denier. Denier is a term you may have heard, and essentially relates to the fineness of the fiber filament. For example, a twelve (12)-denier monofilament is commonly used in sheer pantyhose, and a circular double-knit is about 140-denier.

The clear, viscous resultant solution is filtered and extruded into an aqueous bath of dilute amine oxide, and coagulated into fiber form. This process does not involve any direct chemical reaction and the diluted amine oxide is purified and reused. This makes for a completely contained process fully compatible with all environmental regulations.  

Step 3.  Washing lyocell fiber to remove solvents.

The fiber is then washed before it is dried and twisted or spun into yarns, which are woven or knitted into fabrics and garments. 

No chemical intermediates are formed during the solvent and spinning processes, the minimal product byproduct waste and wastewater are not hazardous, and energy consumption is low. This is the rational for calling lyocell a man-made fiber that is natural in origin.

Step 4.  Drying fiber and producing yarns.

When the filament dries or solidifies, it forms what is called a continuous filament fiber. Many continuous filaments of specific thicknesses collected in a large bundle called a "tow". A tow may contain over a million continuous filaments. The tow bundle is then crimped, in much the same way a curling iron is used to crimp a woman's hair, and is then mechanically cut into staple fibers, usually ranging in length from 1 to 6-1/2 inches, depending how they are to be used.

Strands of continuous filament fibers are then twisted together to form a continuous filament yarn, which is then woven or knit into fabric.

Step 5.  Finishing to produce lyocell fabric.

Due to the nature of lyocell to fibrillate and take dyes poorly, the finishing process is more complicated and takes longer than for other cellulose fabrics.  Lyocell fiber has a relatively low surface energy, which makes it difficult for dyes to bind to it.   As we have seen with other fibers, the dying processes can have a large environmental impact and greatly affect the wear-ability of the garment, especially for those with chemical sensitivities.

Another characteristic of lyocell that is often treated chemically during the fabric manufacturing process is tendency of lyocell to fibrillate or “pill”.  One method to control fibrillation in lyocell is to treat the fabric with an enzyme that attacks cellulose fibers. Many home laundry detergents contain a similar enzyme designed to keep cotton looking newer longer and colors brighter; the cotton symbol is used on these detergent boxes. This enzyme dissolves the split-end hairs from the fiber surface. The fiber is then washed and agitated again. Some secondary fibrillation will occur which produces a fabric that looks sand-washed or like suede.  The resulting fabric is similar in texture and drape to sueded silk or sueded rayon found in fashion apparel. Fabrics processed this way can usually be machine washed and line dried successfully. Tossing these fabrics in the dryer with a damp towel for a few minutes when dry or almost dry will restore the softness and drape. This approach to processing uses the tendency to fibrillate to advantage to create a sand-washed textured fabric.  The enzyme is washed out and becomes part of the waste water that must be treated.

Another alternative to preventing fibrillation is chemical treatments in the last step of fiber and fabric processing. Fabrics processed this way can successfully be machine washed and tumble dried. These fabrics will generally have a smooth surface, such as chino for slacks and jackets, as well as knits for both hosiery and sweaters.  Fabrics labeled as Lyocell® A-100 have been treated with this process.    The environmental impact is that additional chemicals are added to the manufacturing process and become part of the waste treatment process … and problem.

Thickeners of CMC or starch type thickeners are often added to lyocell to prepare the fabric for weaving.  If reactive dyestuffs are used in the dyeing process, the dyestuffs will react to the thickeners so that the dyeing depth of the fiber surface becomes low or uneven dyeing occurs.

The desizing and scouring processes typically require a bath in enzymatic desizing agents and the use of sodium carbonate.  The crumpling process is added with a dye bath lubricant.  Additional enzymatic treatments and strength loss inhibitors are often required to remove fibrillations caused by the crumpling process.  After enzymatic treatment, the enzyme should be deactivated by raising the temperatures to more than 70 and making the pH weakly alkaline by adding sodium carbonate.  If the enzyme remains within the structure of lyocell fiber, the color yield of the fiber will decrease, and furthermore uneven dyeing may occur.

The processes for dyeing lyocell are also complicated and involve a larger number of steps and chemicals than for natural fibers.  The pH and temperature must be carefully controlled depending upon the dyeing process to create an even dyeing and to prevent fibrillation.  Multifunctional reactive dyestuffs are commonly used. 

Fibrillation in Lyocell Fibers.

A better understanding of the lyocell fiber may help explain the variation in care methods. A unique property of lyocell is that the fibers "fibrillate" when wet and are mechanically agitated, like you would get in a washing machine. When the fibers get wet, they swell and become almost "boardy." Fibrillation is the peeling back or splintering of the fiber ends to form tiny "hairs" on the surface. Think of each fiber as a banana. Small fibrils or sections of the fiber splinter and pull away like a banana peel. These surface fibers mat together and detract from the appearance of the finished fabric. Fibrillation can be handled by preventing it from happening or by using it to advantage.

Fabrics made from lyocell that is not specially treated to prevent fibrillation are usually labeled as "dry clean only." Reduced moisture and agitation during dry-cleaning prevent fibrillation. Garments made this way should perform satisfactorily if care recommendations are followed.

Is lyocell ecologically important?

Lyocell is claimed to be a natural, man-made fiber whose manufacturing is environmentally friendly. The raw material for lyocell comes from wood pulp from trees grown on managed tree farms where replanting rates exceed usage or from low-grade recycled paper. The solvent to digest the wood pulp is toxic but about 99% is recovered and recycled.  Waste products in the air and water from the manufacturing process are minimal and considered harmless. Lyocell fiber is eco-friendly since products made from it can be recycled and lyocell is biodegradable because it is a cellulosic fiber; however it will not break down completely if it is disposed of in a landfill.  Products made from lyocell can be recycled, incinerated, or digested in sewage. The fiber will degrade completely in just eight days.

Wood is the most significant replenishable raw material. If forestry work is conducted with care, wood offers the advantage of a very low water consumption and space can be put to optimum use compared to other natural substances. This means that cellulose can be extracted with a high content and the minimum use of extraction agents. 

The process to manufacture lyocell fiber is in fact very nearly a closed loop process in which bleach is not required.  Bleach is commonly required in fabric manufacturing, especially for cotton.  For this reason high quality lyocell products contain no free chlorine and are sold as so-called "TCF - products".  The European Union awarded this process the Environmental Award 2000 in the category "technology for sustainable developments".

So we see that the manufacturing of lyocell fiber does environmental and ecological benefits. Most of concern about lyocell comes from the heavy use of chemicals to turn lyocell fiber into garments.  Tencel is probably not appropriate for those with Multiple Chemical Sensitivities.

What do we offer that is made from lyocell?

At LotusOrganics.com, we offer a few select garments that are lyocell /Tencel blends.  We have tried to find manufacturers that use lyocell that has been lightly treated and undyed.  Your thoughts and comments about lyocell and lyocell garments would be greatly appreciated.  You can email us at CustomerService@LotusOrganics.com.  Also, your feedback on the usefulness of this article would be greatly appreciated.

You can check out the following items:

Raglan Zip Cardigan

Hemp-Tencel Blouse