STUDY

ON REGENERATED FIBERS
REGENERATED FIBERS
• Regenerated cellulosic fibers are made from
cellulose that is extracted from wood pulp, which is
then chemically dissolved and extruded as a
continuous filament, which can be cut into staple
fibers.
• They are called “regenerated cellulosic fibers” due
to 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.
 Types of Regenerated fibers

Cuprammonium
Viscose Rayon Modal Acetate
Rayon

Triacetate Alginic lyocell Polynosic

Viscose Rayon
• Viscose was the first manmade fiber, derived from wood which has excellent properties that can be
engineered and optimized for different textile and nonwoven applications. It is regenerated from viscose
process, which describes the liquid state of the spinning solution.
• Viscose Rayon has a silk-like aesthetic with superb drape and feel and retains its rich brilliant colors. Its
cellulosic base contributes many properties similar to those of cotton or other natural cellulosic fibers. Rayon
is moisture absorbent (more so than cotton), breathable, comfortable to wear, and easily dyed in vivid colors.
It does not build up static electricity, nor will it pill unless the fabric is made from short, low-twist yarns.
• Applications : embroidery thread, chenille, cord, novelty yarns, crepe, gabardine, suiting, lace, outerwear
fabrics and lining for fur coats & outerwear, dresses, saris, jackets, lingerie, linings, milinerey (hats), slacks,
sport shirts, sportswear, suits, ties, bedspreads, blankets, curtains, draperies, sheets, slip covers, tablecloths,
upholstery.
 Physical Properties of Viscose Rayon

Action of
Moisture Tensile Elongation
Density Elasticity Heat and
Absorption Strength at Break Light

15-30% Begins to
3-4.6 gpd at dry elongation at
1.52 g/cm3 13% less than 2-3%. decompose at
stage break 350-400 deg F.

1.9 to 3.0 gpd at

wet stage
Chemical Properties of Viscose Rayon
• Viscose rayon consists of cellulose of lower DP than cotton cellulose. Also amorphous region of Viscose rayon is present to a greater extent,
therefore, Viscose rayon reacts faster than cotton with chemicals. Acids like H2SO4 HCL breaks the cellulose to hydrocellulose. Oxidizing
agents like Na(OCl)2, Bleaching powder, K2Cr2O7, KMnO4– form oxycellulose.
• Inorganic acids such as hydrochloric and nitric can be used in surprisingly strong concentrations provided the temperatures are not too high
and the treatment is brief. Oxalic acid for removal of iron stains is not recommended except at temperatures lower than 150°F. At high
temperatures and concentrations all acid will destroy or carbonize regenerated rayon’s.
• Improper use of soap or use of poorly made soap results in rancidity and odor in rayon fabrics or yarns. When soaps alone is used ,there is a
tendency for the ionized fatty acid from the soap to adhere tenaciously to the individual rayon filaments. During the drying filament of such
materials and subsequent storage .The free fatty acid radical is very likely to turn rancid and to give the goods and objectionable odor.
• Continued heating, however, in the absence of oxygen leads to deterioration of the cellulose but little is known about the course of the
reactions. Short heating at high temperatures, such as 140°C is less harmful than long heating at lower temperatures. A decrease of tenacity
and eventually a yellow to brown discoloration occurs on aging.
• Textile solvents can be used on Viscose rayon without any deteriorating effect. Viscose rayon dissolves in cuprammonium hydroxide
solution.
• Contact with iron in the form of ferrous hydroxide weakens viscose rayon yarns. Therefore staining, marking or touching of rayon to iron or
iron surface should be avoided.
• Microorganisms (moulds, mildew, fungus, bacteria) affect the color, strength, dyeing properties and luster of rayon. Clean and dry viscose
rayon is rarely attacked by moulds and mildew.
CUPRAMMONIUM RAYON
• Cuprammonium or cupro regenerated cellulose is obtained by the cuprammonium process. The name
cuprammonium is obtained from the aqueous cuprammonium hydroxide solvent in which the cellulose is dissolved
to form the spinning solution.

• Cuprammonium rayon is a regenerated cellulosic fiber made from cotton linter pulp or wood pulp dissolved in
cuprammonium solution. Cotton linter is the short downy fiber that enfolds the cottonseed; it is an agricultural by-
product. Cuprammonium rayon is usually made into fine filaments that resemble silk or other luxurious fibers. It is
often used in lightweight fabrications, sometimes in combination with cotton, to make textured fabrics with
slubbed, uneven surfaces. Cuprammonium rayon may also be known as “cupro” or “cupra” and may be referred to
as “ammonia silk.”

• The raw material used in manufacturing cupro is cotton linter which is a natural fiber but after it is mixed with
cuprammonium solution there is a drastic change in its structure. And the natural fiber is converted into
regenerated fiber due to the presence of ammonia, copper, and caustic soda in cuprammonium solution. This is
then made into fine filaments to resemble luxurious fibers like silk. Since cuprammonium rayon fibers do not have
striations or markings hence they are often made into sheer and delicate fabrics like chiffons, satins, nets, etc.
 Properties of CUPRAMMONIUM RAYON

Tenacity Elongation Moisture regain Melting Point Density

1.7-2.3
10-17 % (dry) 11-12.5%. 250 (dec) 1.54 g/cm3
g/denier (dry)

1.1-1.135 (wet) 17-23% (wet)

 MODAL fIBER
• Its raw material comes from natural woods, which can be
naturally degraded after use.
• Its fineness is 1 dtex, while the fineness of the cotton fiber is
1.5-2.5 Tex and the silk fineness is 1.3 dtex.
• Modal fiber is soft and bright and feels especially smooth. Its
draping is better than that of the existing cotton, polyester
and man-made cotton with pure silk luster and touch. It's a
natural silk fabric.
• The Modal fiber has the strength and toughness of synthetic
fibers, with its dry strength of 3.56 cn/ Tex and its wet
strength of 2.56 cn/ Tex. Its strength is higher than that of
pure cotton and polyester cotton, reducing the breakage in
processing.
MODAL fIBER
• Its moisture absorption capacity is 50% higher than that of cotton fiber,
which keeps the Modal fiber fabric dry with good air penetrability. It is the
ideal fabric for human body and healthy clothing products, beneficial to
the physiological circulation and health.
• Compared with cotton fibers, the Modal fiber has good shaping and
dimensional stability so that it has natural anti-wrinkle and non-ironing
properties, making it more convenient and natural to wear.
• Its dyeing property is good and after many times of washing, it remains
new and bright with good moisture absorption and color durability.
Compared with pure cotton, it is more comfortable to wear and does
not have the disadvantage like pure cotton clothes of fading easily and
turning yellow. Therefore, the fabric is bright in colors and stable in
texture. After 25 times of washing, the cotton fabric feels harder, while
Modal fiber fabric is the opposite.
• Modal fabrics is close to the polyester in strength (35cn/Tex). Its wet
strength is slightly lower than that of the cotton with softness, smoothness
and the silk touch. The dry extension of the fibers is between that of cotton
and viscose. Its wet elongation is similar to that of cotton but less than that
of viscose. Its shrinkage rate is low and its good moisture absorption
capacity is 50 % higher than that of cotton with extremely fast moisture
absorption capacity.
Acetate fiber
• Acetate fibers are one of the principal types of synthetic fibers. The fiber forming
substance is cellulose acetate in which at least 92% of the hydroxyl groups are
acetylated. This fiber is called triacetate or triacetate cellulose. Secondary acetate
contains only about 76 percent acetylated cellulose groups. The diacetate fiber is
officially called acetate while the triacetate cellulose is called triacetate.
• Conventional secondary acetate fibers can be manufactured by treating wood pulp,
cellulose or cotton linters with acetic acid. The pretreated cellulose or secondary
acetate is converted to triacetate when treated with acetic anhydride in the
presence of an acid catalyst.
• Acetate fibers, the so-called acetate silk fibers, are molded from solutions of
cellulose acetate in organic solvents, usually a mixture of methylene chloride and
alcohol (triacetate), or acetone (secondary acetate).
• Acetate fibers are soft and pleasant to the touch. They are dyed only with special
types of dyes, which are unsuitable for most other fibers. Triacetate fibers are less
hygroscope and have a greater elasticity and wrinkle resistance than articles made
of diacetate fibers.
Acetate fiber
The tensile strength of acetate fibers is rather low. The loss of strength upon moist testing is up to 45 percent for acetate fibers and up to 20
percent for triacetate fibers.

Acetate fibers have a low thermal stability. For this reason, articles made of acetate fibers have to be ironed through a damp cloth. Furthermore,
acetate fibers have a low stability in the presence of dilute solutions of alkalis. Other disadvantages of acetate fibers include low durability and high
tendency to gather static electricity. To offset or remedy these deficiencies, acetates are often chemically modified or blended with other fibers.

Cellulose acetate fibers can be de-acetylated by sodium hydroxide saponification under controlled conditions. The product is a true regenerated
cellulose filament. This process was developed by Celanese who called the fiber “Fortisan”. The fibers generic name is Rayon. It has outstanding
strength and low elongation and finds many industrial uses where these two properties are required.
 Physical Properties of Acetate

Elongation Action of
Moisture
Density Fineness at Break Heat and
Absorption
Light

1.25 to 6.5%
1.5 to 4.1 250 deg
16-18%
1.33 g/cm3 denier F.
Chemical Properties of Acetate
Effect of alkalis: It is stable to water even at a boil Effect of acids: It is unaffected by a thin solution
and can withstand soap solutions and alkalis at but is attacked by strong acids. The degradation of
normal temperatures. molecules occurs and the chain breaks.

Effect of oxidizing agents: Mild oxidizing agents Effect of organisms: It is resistant to attack by
may be utilized i.e. chlorine is old and mild bacteria and mildew but it is attacked by the
peroxide. moth which makes holes in the fabric.
lyocell

Lyocell is made from cellulose found in wood pulp which has been harvested from tree farms.

The fiber is produced via an advanced 'closed loop' solvent spinning process, with minimum impact on the environment and economical use of energy and water. Lyocell uses an amine
oxide as a non-toxic solvent which is continually recycled during the production process.

Lyocell fibers are produced by regenerating cellulose into an organic solvent, N-methyl morpholine-N-oxide hydrate, which is non-toxic and biodegradable, and almost completely
recyclable.

The life cycle of a lyocell fiber has a minimal environmental impact and is significantly more durable than natural fibers such as synthetic fibers or cotton derived from oil; it uses less
land, irrigation, pesticides, or fertilizers to grow eucalyptus or beech trees from which lyocell fiber is made if the forests are managed sustainably in the case of cotton.
lyocell
• Lyocell fabric is considered a durable fabric because it is made of wood and therefore biodegradable and compostable.

• It can be blended with other fabrics like cotton, polyester, acrylic, ethical wool, and peace silk
• It is breathable, strong, and gentle on the skin with a soft, silky texture

• It is stretched and efficient in absorbing moisture, making it a great alternative to activewear

• Instead of viscose and other types of rayon, lyocell is made using a closed-loop process which means that the chemicals used in the
production are not released into the environment.

• A major disadvantage is that lyocell is not as economical as other fibers like cotton at present.
• Lyocell fiber is similar in many respects to viscose rayon fiber, but exhibits enhanced properties in terms of softness, drapability,
dimensional durability, dye acceptance, and colorfastness.
• Moisture regain of lyocell fiber is about 11%, slightly less than viscose-rayon.
• The dry tenacity value of lyocell fiber is higher than that of viscose and HWM rayon fiber.
• It is the only regenerated cellulose fiber that has a wet tensile strength greater than the wet energy of cotton.
• It has a significantly reduced elongation value slightly higher than HWM rayon fiber
• It has a close to circular cross-section that's longitudinal surface is very smooth and cylindrical without any striation.
• It can be hand washable
• It is fibrillated during wet processing to produce special textures.
• It is also biodegradable.
 Polynosic fiber
• The polynosic rayon fibres represent a fair attempt to reduce the degree of
disadvantage suffered by viscose in relation to cotton. By selecting good quality
pulp and reducing the severity of chemical treatments a higher molecular chain-
length is preserved (500–700 as compared with 240–270 of viscose rayon) and a
microfibrillar structure akin to cotton is obtained by controlled precipitation.
• The polynosic fibers have a round cross-section, while viscose rayon has a
serrated cross-section.
• The advantages achieved by way of higher tenacity, ratio of wet-to-dry tenacity,
wet modulus, etc.
• High wet modulus and good elastic recovery are the most important features of
polynosics.
• They differ from ordinary viscose by having better dimensional stability, ability
to withstand mercerization more crispiness, and lower water imbibition. By and
large, the wet processing methods used for cotton could be applied to
polynosics.
• The manufacturing process of polynosic fibers is nearly the same as that of
rayon fibers. However, the wet tenacity is improved and has both similar
characteristics of cotton fibers and excellence of silk fibers.
• Polynosic is a type of microfibre that is a blend of polyester and rayon fibres, with a soft, silky finish. It wicks
moisture from the wearer, leaving a cool feeling on the skin.
• Fabrics of fine count/denier yarn is possible thanks to the high tenacity. Thus, polynosic fabrics have excellent luster as
the silk fabric and dry tactile feeling. In addition, because polynosic fibers are friendly with other types of fibers, they are
suitable for blended and union cloth.
• Laundering will make little shrinkage and shape deformation.
• Resistant to acid and alkali. Fabrics blended with cotton may be mercerized or sanforized.