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Regenerated Fibers_.pdf

The document discusses different types of regenerated cellulosic fibers, including their production processes and properties. Viscose rayon is the first man-made fiber derived from wood pulp. It has properties similar to cotton or other natural fibers. Cuprammonium rayon is made by dissolving cellulose in a cuprammonium solution. Modal fiber is soft and smooth with strength comparable to polyester. Acetate fibers are made from cellulose acetate and include triacetate and secondary acetate. Regenerated fibers combine natural cellulosic raw materials with chemical manufacturing processes.

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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 Viscose Rayon Cuprammonium Rayon Modal Acetate 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 Density 1.52 g/cm3 Moisture Absorption 13% Tensile Strength 3-4.6 gpd at dry stage 1.9 to 3.0 gpd at wet stage Elasticity less than 2-3%. Elongation at Break 15-30% elongation at break Action of Heat and Light Begins to decompose at 350-400 deg F.
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 1.7-2.3 g/denier (dry) 1.1-1.135 (wet) Elongation 10-17 % (dry) 17-23% (wet) Moisture regain 11-12.5%. Melting Point 250 (dec) Density 1.54 g/cm3
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 acetatefibers is ratherlow. The loss of strength upon moisttesting isup to 45 percent for acetate fibers and up to 20 percent for triacetatefibers. Acetatefibershave a low thermalstability.For thisreason, articles madeof acetatefibers haveto be ironed through a damp cloth. Furthermore, acetate fibershave a low stabilityin the presenceof dilutesolutions of alkalis. Other disadvantagesof acetatefibers includelow durabilityand high tendency to gather staticelectricity.To offset or remedy these deficiencies,acetatesare often chemically modifiedor blended with other fibers. Cellulose acetatefibers canbe de-acetylatedby sodium hydroxidesaponificationunder controlled conditions.The product is a true regenerated cellulose filament.This process was developed by Celanese who called the fiber “Fortisan”.The fibers generic nameis Rayon. It hasoutstanding strength and low elongation and findsmany industrialuses where these two propertiesare required.
Physical Properties of Acetate Density 1.25 to 1.33 g/cm3 Moisture Absorption 6.5% Fineness 1.5 to 4.1 denier Elongation at Break 16-18% Action of Heat and Light 250 deg F.
Chemical Properties of Acetate Effect of alkalis: It is stable to water even at a boil and can withstand soap solutions and alkalis at normal temperatures. Effect of acids: It is unaffected by a thin solution but is attacked by strong acids. The degradation of molecules occurs and the chain breaks. Effect of oxidizing agents: Mild oxidizing agents may be utilized i.e. chlorine is old and mild peroxide. Effect of organisms: It is resistant to attack by bacteria and mildew but it is attacked by the moth which makes holes in the fabric.
lyocell Lyocell is made fromcellulose foundin woodpulp which has beenharvestedfromtree farms. The fiber is produced via an advanced'closedloop' solventspinning process, with minimumimpact on the environmentandeconomicaluse of energy andwater.Lyocell uses an amine oxideas a non-toxicsolventwhich is continuallyrecycled duringthe production process. Lyocell fibersare producedby regeneratingcelluloseinto an organicsolvent, N-methyl morpholine-N-oxidehydrate,whichis non-toxicandbiodegradable,andalmostcompletely recyclable. The life cycle of a lyocell fiberhas a minimalenvironmentalimpactandis significantly moredurablethannaturalfiberssuch as synthetic fibers or cotton derivedfromoil; it uses less land, irrigation,pesticides, or fertilizersto grow eucalyptus or beech treesfrom whichlyocell fiberis madeif the forestsare managedsustainablyin 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.
Regenerated Fibers_.pdf