LYOCELL AND SPANDEX

THE NEW AGE FIBRES

By: Bademaw Abate (Lecturer)

INTRODUCTION Lyocell (lyo from Greek: lyein = dissolve, cell from

cellulose) Man made cellulosic fibres Produced by regenerating cellulose into fibre form

out of a solution (solvent spinning) of cellulose in an organic solvent

‘Organic solvent’ - mixture of organic chemicals and water

‘Solvent spinning’ means dissolving and spinning without the formation of a derivative

Tencel is the brand name of Lyocell

RAW MATERIALS Cellulose • Most abundant natural resource on earth.• It is obtained from wood pulp.• Trees like Eucalyptus , bamboo and pine tree are used.• Eucalyptus is primarily used to produce the Tencel fibre.

NMMO• Chemically produced from N methyl morpholine and hydrogen peroxide• Cyclic amine oxides such as N-methyl morpholine oxide have the capacity to

dissolve cellulose.• NMMO exists in several degrees of hydration.• At room temperature it is a crystalline mono hydrate and melts at 72 degrees• When heated at 100 C, mono hydrate NMMO is able to dissolve readily several

percentages of high molecular weight cellulose.• Cellulose dissolution in NMMO is found to depend on:

– The temperature of the solution

– The water content of the mixtures

– The concentration and the degree of

– Polymerisation of the cellulose

MANUFACTURING AND PROCESSING

Preparing Wood Pulp• Hardwood trees are harvested and logs are

taken to mill.• Wood is cut into small chip and fed into a

chemical digesters which removes lignin and softens them into wet wood pulp.

• It is then washed with water, bleached and dried into huge sheets of cellulose and rolled onto spools.

Dissolving Cellulose• Spools of cellulose are unrolled

and broken into one square inches.

• It is then loaded into heated pressurized vessel containing N-methyl morpholine N-oxide.

• Cellulose dissolves into a clear solution.

Filtering• In Amine Oxide solvent, cellulose is dissolved into a clear solution.• It is then pumped out and filtered.

Spinning• Cellulose is forced through the spinnerets and long strands of fibre comes

out.• These fibres are then dissolved in dilute Amine Oxide solution and is later

washed with water.

Drying And Finishing• Fibre is passed through drying area.• In the drying area, water is evaporated and lubricant is applied which

may be soap, silicone or other agent.

PROPERTIES Soft, strong, absorbent Fibrillated during wet processing to produce special textures It has high wet and dry strength, it is stronger than Cotton and Wool. Wrinkle resistant Very versatile fabric, dyeable to vibrant colours, with a variety of effects and

textures. Can be hand washable Simulates silk, suede, or leather touch Good drapability Biodegradable Fine yarn counts can be spun

Comfort• Soft, smooth fibre.• Ideal for apparel that contacts skin.• Thermal retention is poor.

Appearance Retention• Resiliency is moderate- Wrinkles but not as severely as rayon.• Shrinks, but not progressively.• May have problems with fuzziness or piling.

Aesthetics• Lustre, length and diameter can be changed depending upon end

use.• Processed to produce a range of surface effects.• Offers unusual combinations of strength, opacity, absorbency.

Durability• Performs more like cotton than rayon.• Strongest of cellulosic fibres.• Unique combination of soft hand and good durability, produces

comfortable, long-lasting textiles for apparel and interiors.

Care• Either gently machine- Washable or dry cleaned.• Sensitive to acids.• Resistant to mild alkalis.• Sensitive to mildew and some insects.• High dye affinity.• High inherent whiteness- Bleaching is not necessary.

PHYSICAL STRUCTURE

The physical structure is a more rounded cross section & smoother longitudinal appearance than rayon.

 Since in the case of Lyocell we are just dissolving cellulose in NMMO and not making any cellulose derivatives, it has a different molecular structure than other regenerated cellulosic fibres.

The structure is ‘Homogeneous’ and ‘Dense’.

Cross Section

Longitudinal Section

APPLICATIONS Professional business wear. Leotards Hosiery Casual wear Upholstery Window-treatment fabrics Filters Printers’ blankets Specialty papers Medical dressings Conveyer belts for strength &

softness Botanic Tencel bed

Botanic Bed

Spandex in the World of Fashion

We all have grown into believing that fashion is not only the outer appearance. It deals mainly with your inner comfort and sense of freedom in whatever you are wearing.

Fashion is what gives birth to our individual styles and individual style is driven by a strong feeling of one’s own comfort and ease.

Fashion & its New Age Meaning

Spandex is a synthetic fibre known for its exceptional elasticity. When first introduced, it revolutionized many areas of the clothing industry. Polyurethanes are called polyurethanes because in their backbones they

have a urethane linkage.

SPANDEXSTRONGER AND MORE DURABLE THAN RUBBER.

There are two types of spinning are available for spandex, these are-

Dry-spinning process. Wet-spinning process.

Spinning process-

Dry/wet spinning-

Polymer reactions- The first step in the production of spandex is the production of the prepolymer. This

is done by mixing a macroglycol with a diisocyanate monomer. The compounds are mixed in a reaction vessel and under the right conditions they react to form a prepolymer. Since the ratio of the component materials produces fibers with varying characteristics, it is strictly controlled. A typical ratio of glycol to diisocyanate may be 1:2.

In dry spinning fiber production, the prepolymer is further reacted with an equal amount of diamine. This is known as a chain extension reaction. The resulting solution is diluted with a solvent to produce the spinning solution. The solvent helps make the solution thinner and more easily handled. It can then be pumped into the fiber production cell.

 

An important spandex fiber with its properties-

The above diagram is an example of the molecular structure of 'Lycra-Spandex' type

moleculesn = a very large number of repeating double 'molecular segments' in the polymer chain.

x is the variable number of units in the 'elastic' molecular segment, this gives differing degrees

of 'stretchiness'.Therefore its molecules have a stretchy section

that make it soft and rubbery, and a rigid section that makes it tougher than rubber.

Lycra is an artificial fiber that readily stretches but is still a strong material overall.

Parts of the long polymer molecules stretch easily i.e. elastic at the molecular level, but other

sections of the polymer chain are more rigid to increase strength.

Lycra fibers can be stretched upto 500% (i.e. 5x) of their original length.

Producing the fibers- The spinning solution is pumped into a cylindrical spinning cell where it is

cured and converted into fibers. In this cell, the polymer solution is forced through a metal plate, called a spinneret, which has small holes throughout. This causes the solution to be aligned in strands of liquid polymer. As the strands pass through the cell, they are heated in the presence of a nitrogen and solvent gas. These conditions cause the liquid polymer to chemically react and form solid strands.

As the fibers exit the cell, a specific amount of the solid strands are bundled together to produce the desired thickness. This is done with a compressed air device that twists the fibers together. In reality, each fiber of spandex is made up of many smaller individual fibers that adhere to one another due to the natural stickiness of their surface.

Spandex Fiber Characteristics- Can be stretched repeatedly and still recover to very near its original length and shape Generally, can be stretched more than 500% without breaking Stronger, more durable and higher retractive force than rubber Lightweight, soft, smooth, supple In garments, provides a combination of comfort and fit, prevents bagging and sagging Heat-settable — facilitates transforming puckered fabrics into flat fabrics, or flat fabrics

into permanent rounded shapes Dyeable Resistant to deterioration by body oils, perspiration, lotions or detergents Abrasion resistant When fabrics containing spandex are sewn, the needle causes little or no damage from

“needle cutting” compared to the older types of elastic materials Available in fiber diameters ranging from 10 denier to 2500 denier Available in clear and opaque lusters

You can find this comfort and freedom in clothes which keep you the way you want to stay.

Fashion is when you dress up exactly how you should for an occasion and how comfortable you are in it!

You should choose fibers according to your body type and personal choice. It should basically give you the liberty to be yourself. Spandex is one such fiber.

It is highly stretchable and expands to a degree which ensures your complete comfort.

Basic Properties of Spandex

Spandex fiber is one of the most popular fibers nowadays as it is used in most dress materials to make it stretchable and to give your body the desirable shape you want to.

It is, in its true sense the freedom fiber which helps you keep up to your daily life and all activities you want to do.

athletic, aerobic exercise apparel swimsuits ski pants disco jean hosiery socks underwear surgical hose support hose motion capture suits Home furnishings

USESGarments made with LYCRA® fiber are comfortable, durable and keep their fit.

THANK YOU!