Man made fiber

Manufacturing of man-made fiber

1. Man-made Fiber Book References: 1. Hand Book of Textile Fibers 1- Natural Fibers by Cook. J. Gordan . 2. Dyeing and Chemical Technology of Textile Fibres by E.R. Trotman 3. Textile Fibres , Dyes & Processes by Howard L. Needles 4. Textiles: Fiber to Fabric by Corbman , Bernard P 5. Textile Fibers by Mathews (John Wieley & Sons Inc.) 6. Man Made Fibres by R.W Moncrieff 7. Apparel Fibers by Dr. Engr. Md. Nazirul Islam 8. A Text Book of Fiber Science and Technology by S.P. Mishra  

2. Textile Fiber A fiber that can be spun into yarn or processed in textile by means of any appropriate process is termed as textile fiber. To be a textile fiber a fiber should have some properties like length, strength, flexibility, elasticity, fineness, uniformity etc.

3. Fiber

4. Regenerated Fiber Regenerated fiber is created by dissolving the cellulose area of plant fiber in chemicals and making it into fiber again (by viscose method). Since it consists of cellulose like cotton and hemp, it is also called "regenerated cellulose fiber.“ Example- Lyo -cell, Viscose etc. Chemical fiber/Synthetic fiber The fiber which is produced by the reaction of different chemical or by the polymerization of different chemical is called synthetic fiber. Example- Polyester, Nylon, Acrylic etc.

5. The main source for the formation of synthetic fibers are- Petroleum, Natural gas deposits, Coal. Characteristics of fiber forming polymers Flexibility: The polymer must be a linear flexible macromolecule with a high degree of symmetry. Molecular mass: The polymer must have a comparatively high molecular mass. Crystallinity : The fiber forming polymer should have high degree of crystallinity . Orientation: A high degree of orientation of the molecules in the polymer is a pre-requisite for producing good tensile strength.

6. History of Man-made Fiber Year Fiber Year Fiber 1910 Rayon 1949 Olefin 1924 Acetate 1950 Acrylic 1930 Rubber 1953 Polyester 1936 Glass 1959 Spandex 1939 Nylon 1961 Aramid 1939 Vinyon 1983 Sulfar 1946 Metallic 1992 Lyocell 1949 Modacrylic

7. Classification of chemical fiber

8. Advantage and disadvantage Advantage/Significance/Important More stronger than natural fiber. Do not depend on agricultural production. Do not easily degrade by moisture, chemicals or bacteria. Cheaper than natural fiber. Any shape can be given as the cross-section shape depend on spinneret. Production rate is high.

9. Disadvantage Not comfortable as natural fiber. Synthetic fibers are hydrophobic, so easily can not be dyed. Form static electricity which cause of discomfort.

10. Fiber Formation The formation of synthetic fibers from polymers involves the following principle: Reduction of the polymeric material to a liquid state by melting or by dissolving in a solvent or in some solubilizing agent. Extrusion of liquid under pressure through fine holes of a spinneret. Rapid and continuous solidification of the extruded liquid.

11. Synthetic fiber spinning method Spinning method of synthetic fiber formation are determined by the physical and chemical properties of the polymer. Due to different solidification process

12. Spinneret A spinneret is a device used to extrude a polymer solution or polymer melt to form fibers. Streams of viscous polymer exit via the spinneret into air  or liquid leading to a phase change which allows the polymer to solidify.

13. Melt Spinning Melt spinning uses heat to melt the polymer to a viscosity suitable for extrusion. This type of spinning is used for polymers that are not decomposed or degraded by the temperatures necessary for extrusion. This method is used by 70% of the fibers. Example:  Melt spinning is used for the production of polyester, nylon, olefin, saran and glass fibers.

14. Melt Spinning Process

15. Spinning Process In melt spinning, polymer is heated and it melts to form a liquid spinning solution or dope. Chips of polymers are fed to a hopper which is heated. There is a grid (sieve) at the base which permits only molten liquid to pass through. Then the solution is purified by filter. The molten polymer is extruded at high pressure and constant rate through a spinneret into a relatively cooler air stream that solidifies the filaments. Finally the filament yarn either is immediately wound onto bobbins or is further treated for certain desired characteristics or end use.

16. Advantages:  High speed (Production rate 8000 m/min.). No solvents. As no solvent is used, washing is not required. No purification problems. Cost effective. Disadvantages: Separate drawing step. Accurate temperature control is critical. All types of polymer can not be converted to fiber in this process.

17. Dry spinning Dry spinning is used for polymers that need to be dissolved in a solvent. Solvent spinning (dry spinning and wet spinning) are used by 30% of the fibers. Dry spinning is used to form polymeric fibers from solution. Dry spinning is used for those polymer which can not be melt spun. Example:  Dry spinning is used in the production of acetate, triacetate and some acrylic, modacrylic , spandex and vinyon (PVC,PVA) fibers.

18. Dry Spinning Process

19. Spinning Process In dry spinning, a volatile solvent is used to dissolve the raw materials and form a solution. Then the solution is purified by filter. The solution is extruded through a spinneret into a warm air chamber where the solvent evaporates, solidifying the fine filaments. Finally the filament yarn either is immediately wound onto bobbins or is further treated for certain desired characteristics or end use.

20. Advantages: Yarn does not require purification. Suitable for heat sensitive polymer. More suitable for filament yarn. Disadvantages: Flammable solvent hazards The process required solvent and so solvent recovery process. Slow (200-400 yds /min). Additional post spinning operation is required for complete solvent removal.

21. Wet Spinning This is the oldest, most complex and also the most expensive method of man-made yarn manufacture. This type of spinning is applied to polymers which do not melt and dissolve only in non-volatile or thermal unstable solvents. Example:  Wet spinning is used in the production of aramid, Lyocell , PVC, Vinyon (PVA), viscose rayon, spandex, acrylic and modacrylic fibers.

22. Wet Spinning Process

23. Spinning Process In wet spinning, a non-volatile solvent is used to convert the raw material into a solution. The solvent is extruded through the spinneret either by simply washing it out or by a chemical reaction between the polymer solution and a reagent in the spinning bath. After extrusion, the solvent is removed in a liquid coagulation medium. Finally the filament yarn either is immediately wound onto bobbins or is further treated for certain desired characteristics or end use.

24. Advantages: Can be used for any polymer. Maximum fiber strength can be achieved. Disadvantages: The production rate is low (70-150 yds /min). More costly Washing is necessary to remove impurities. Solvent and chemical recovery process is required.

25. Dope Dyeing/Solution dyeing Manufactured fibers are solution dyed. In solution dyeing, the dye is added to the thick liquid before it is forced through the spinneret.

26. Different fiber structure and their effects on fiber properties Fiber structure Effects on fiber properties Fiber length Strength Molecule orientation Strength Fiber diameter Performance and hand feel Length to diameter ratio Spinnability Circular cross-section Luster of the fiber

27. Yarn texturing Texturing  is the process by which synthetic fibres are modified to change their texture - the physical appearance of the  fibre . Texturing techniques can include bulking (where thermoplastic  fibres are twisted, heat set and untwisted), crimping and coiling, amongst others. Texturing takes advantage of the thermoplastic nature of synthetic fibres and uses it to set texturised features in place. Fibres may be texturised to improve the fibre's insulation properties (as processes like bulking allow it to trap air better), to minimise a shiny, synthetic-looking appearance, to reduce the silky nature of the fibre or to create special effects (fancy yarns).

28. These modifications will also affect the eventual fabric, and fibres may be folded, looped, coiled or crinkled in order to improve the drape, appearance, lustre , warmth, elasticity or handle of the finished fabric. Texturising can reduce the "synthetic" appearance of a finished fabric, bringing its appearance closer to that of a natural fibre fabric. Texturing is a procedure used to increase the volume and the elasticity of a filament fibres . The essential properties of textured yarns and the products made from them are softness, fullness, a high degree of elasticity, thermal insulation and moisture transporting properties. All yarns which can be shaped by heat are suitable for texturing. The prime purpose of texturing filament yarn is to create a bulky structure. The process of introducing crimp, loop, coils to continuous filament yarn is called texturing. It stabilizes the synthetic yarn through heating and drawing.

29. Method of texturing Gear crimping False twisting Knit-de-knit Stuffer box

30. Purpose of texturing The prime purpose of texturing filament yarn is to create a bulky structure that is desirable for the following reason: The voids in the structure cause the material to have good insulation properties. The voids in the structure change the density of the material (Which make a light weight yarn with good covering properties). The sponge like structure feels softer than a regular twisted flat yarn. The crimped or coiled filament structure gives a higher elasticity than a flat yarn. The less oriented surface structure of the yarn gives dispersed light reflection which give a desirable dull appearance.

31. The End

32. Regenerated Fibers Regenerated fibers are found by the modification of vegetable or protein fiber. Properties of regenerated fiber: Give higher strength and the properties of natural fiber. Fibers are hydrophilic. Easily dye-able. Easily washable and cross-section can be changed. Regenerated fiber can be produced from cellulose fiber or from protein fiber. Regenerated cellulosic fibers are: Viscose, Cuprammonium , Acetate, Lyo -cell etc. Regenerated protein fibers are: Casein fiber, Vicara fiber, Ardil fiber etc.

33. Rayon Fiber Cellulose based man-made fiber is termed as Rayon fiber. During it’s development, it has designated by various name such as artificial silk, wood silk, fiber silk, art silk etc. The implication in this name is that, it was originally intended to be a substitute for silk. Rayon is a manufactured fiber composed of regenerated cellulose in which substituents have replaced not more than 15% of the hydrogen of the hydroxyl group. Types of regenerated cellulose or rayon fiber: Regenerated by viscose process (viscose fibers) Regenerated by cuprammonium process ( cuprammonium fibers) Regenerated by lyocell process ( lyocell fibers) Regenerated by acetate process (acetate fibers) Acetate fibers is also called cellulose ester fibers which also divided into two categories: 1. Acetate fibers and 2. Triacetate fibers

34. Viscose Rayon/Artificial Silk Viscose is a man made, natural polymer, cellulosic or regenerated cellulose filament or staple fiber. According to U.S. Federal Trade Commission “Rayon is a manufactured fiber composed of regenerated cellulose in which substituent’s have replaced not more than 15% of the hydrogen’s of the hydroxyl groups”. Chemical reaction for viscose rayon production : The cellulose is treated with 17.5% solution of NaOH which converts cellulose into soda-cellulose. Cell-OH + NaOH → Cell- ONa + H 2 O Cellulose                    Soda-cellulose 2. The soda cellulose reacts with carbon disulphide to form sodium cellulose xanthate . Cell- ONa + CS 2 → Cell-O-CS- SNa Sodium cellulose xanthate . 3. Then it is dissolved in a dilute solution of caustic soda. It is extruded into H 2 SO 4 which regenerates the cellulose in the form of long filaments. Cell-O-CS- SNa + H 2 SO 4 → Cell-OH + Na 2 SO 4                                               Regenerated cellulose

35. Flow Chart of Viscose Rayon Production Cellulose pulp ↓ Steeped in warm caustic soda for an hour ↓ Pressed to remove excess solution ↓ Powdery Crumbs ↓ Aged for up to a day (formation of soda cellulose) ↓ Mixed with carbon disulphide (formation of sodium cellulose xanthate ) ↓ Mix into a dilute caustic soda solution (to give a viscose solution) ↓ Ripening for up to a day (Regenerated cellulose) ↓ Spinning

36. Viscose fiber formation process consists of the following of the structural modifications: Swelling of cellulose with the hydrates of NaOH . Breakage of crystalline and amorphous parts. Replacement of the hydroxyl group by xanthate group. Removal of xanthate group in spinning and then sodium groups by hydroxyl groups. Formation of vander waals forces and hydrogen bonding. Formation of regenerated cellulose structure. Viscose manufacturing technology mainly consists of the following three stages: Purification of cellulosic material. Preparation of cellulose xanthate solution. Fiber formation and regeneration of cellulose.

37. Manufacturing Process It is a regenerated cellulosic fiber and cellulose is the raw material for producing this man made fiber. The raw material is obtained from a special variety of wood called spruce. Purification of Cellulose: The manufacture of viscose rayon starts with the purification of cellulose. Spruce trees are cut into timber. Their barks are removed and cut into pieces measuring 7/8" x 1/2" x 1/4". These pieces are treated with a solution of calcium bisulphite and cooked with steam under pressure for about 14 hours. The cellulosic component of the wood is unaffected by this treatment but the cementing material called lignin, which is present in the wood, is converted into its sulphonated compound which is soluble in water. This can be washed off, thereby purifying the remaining cellulose. This cellulose is treated with excess of water. After this it is treated with a bleaching agent and finally converted into paper boards or sheets. This is called wood pulp, which is normally purchased by the manufacturers of viscose rayon. 

38. 2. Conditioning of Wood Pulp: The pulp sheets are cut by a guillotine to the required dimension and are kept in a special room. Air moves freely among the divisors by means of ventilators, the temperature is maintained at 30 ºC . In this way the desired moisture content can be had. 3. Steeping Process: The conditioned wood pulp sheets are treated with caustic soda solution (about 17.5%). It is called mercerising or steeping. The high DP cellulose (1000) is converted into soda cellulose. The sheets are allowed to soak until they become dark brown in color. This takes about 1-14 hours. The caustic soda solution is drained off and sheets are pressed to squeeze out excess caustic soda solution. 100 kg of sulphite pulp gives about 310 kg of soda cellulose.  4. Shredding or cutting process: The wet, soft sheets of soda cellulose are passed through a shredding machine which cuts them into small bits. In 2-3 hours the sheets are broken into fine crumbs.

39. Viscose Rayon Production Process

40. 5. Ageing Process:   To obtain almost ideal solution of cellulose, the soda cellulose is stored in small galvanised drums for about 48 hours at 28C. This process is called ageing process. The ageing process is essential. During This process, the DP od soda cellulose is decreased from 1000 to about 300 by oxygen present in the air, contained in the drum. 6. Churning Process or Xanthation :   After ageing, the crumbs of soda cellulose are transferred to rotating, air tight, hexagonal churners or mixers. Carbon disulphide ( 10% of the weight of the crumbs) is added to the mixer and churned together for 3 hours by rotating the mixers at a slow speed of 2 rev per minutes. Sodium cellulose xanthate is formed during this process and the colors of the product changes from white to reddish orange.

41. 7. Mixing or dissolving Process:   The orange product i.e. soda cellulose xanthate is in the form of small balls. These fall into a mixer called dissolver which is provided with a stirrer. A dilute solution of caustic soda is added, and the contents are stirred for 4-5 hours and at the same time, the dissovler is cooled. The soda cellulose xanthate dissovles to give a clear brown thick liquor, similar to honey. This is called 'viscose' and it contains about 6.5% caustic soda and 7.5% cellulose. 8. Ripening Process:   This viscose solution requires to be ripened to give a solution having best spinning qualities. Ripening is carried by storing the viscose solution for 4-5 days at 10 to 18 deg. The viscosity of the solution first decreases and then rises to its original value. The ripened solution is filtered carefully and is now ready for spinning to produce viscose rayon filaments.

42. 9. Spinning Process:   The viscose solution is forced through a spinneret, having many fine holes ( 0.05-0.1mm) diameter. The spinneret is submerged into a solution containing the following chemicals. 10% Sulphuric acid, 18% Sodium sulphate, 1% Zinc sulphate, 2% glucose, 69% water. The spinning solution is kept at 40-45 ºC . Sodium sulphate precipitates the dissolved soda cellulose xanthate . Sulphuric Acid converts xanthate into cellulose, carbon disulphide and sodium sulphate . The glucose is supposed to give softness and pliability to the filaments whereas zinc sulphate gives added strength. As a number of filaments emerge from the spinneret, they are taken together to an eye at the surface of the spinning bath and then guided to two rollers from where they are wound on to a spindle.

43. The quality of viscose rayon filament formed depends upon : 1. The temperature of the spinning bath 2. The composition of the spinning bath. 3. The speed of coagulation. 4. The period of immersion of the filament in the spinning bath. 5. The speed of spinning. 6. The stretch imparted to the filaments.

44. Role of Zinc in Spinning Bath In the non-zinc spinning process under normal conditions of acid concentrated in the spinning bath, cellulose xanthate gel is converted into cellulose xanthic acid and then to cellulose. The process is very fast and regeneration takes place before the cellulose molecules can properly oriented. This result in a rather disorientation matrix with poor crystalline organization. The net result is a regenerated cellulose filament with poor dry strength and a very interior wet strength. So the zinc result in a transient zinc cellulose xanthate complex which is more stable against acid induced regeneration. Zinc being bivalent form a transient cross link between the adjustment xanthate groups. Coupled with crosslinking the strong deswelling action of zinc xanthate gel which can be stretched to a highly oriented structure with small crystal size and relatively large crystals.

45. Physical properties of Viscose Rayon : Moisture absorption: Viscose rayon absorbs moisture more than cotton. Viscose rayon moisture content 13% at 65% relative humidity. Tensile strength: Less tensile strength than cotton in wet condition. Elasticity: Less elasticity than cotton, about 2-3% less. Abrasion resistance: Low. Flammability: Like as cotton. Melting temp: Do not decompose at 176ºC to 204ºC.

46. Chemical properties of viscose rayon : Effect of acid: Acid like H 2 SO 4 or HCl, break down the macromolecules of viscose and produce hydro-cellulose. Dilute acid for short time do not attack. Effect of alkali: Concentrated alkali causes swelling and reduces strength. But week alkali does not damage. Effect of bleaching: Viscose can withstand both oxidizing and reducing bleaches. Biological agent: Mildew, bacteria etc. affect the color, strength and luster of rayon. Dye affinity: Better affinity for dyes than cotton. Flammability: Burns rapidly.

47. Application of Viscose Rayon Yarn: Embroidery, chenille, cord, novelty yarns, sewing thread. Fabric: Crepe, gabardine, suiting, lace, outwear fabrics and lining of coats and outwear. Apparel: Dresses, blouses, saris, jackets, lingerie, linings, military hats, slacks, sport shirts, sports-wear, suit, ties, work cloth, evening gowns. Domestic textiles: Bead spreads, Bed sheets, blankets, curtain, draperies, slip covers, table cloths, chair cover, cushions, furnishing cloth etc. Industrial textiles: High tenacity rayon is used as reinforcement to mechanical rubber goods(tires, conveyor belts, hoses) applications within aerospace (tire cord of air craft), agricultural textile industries, braided cord, tapes, power transferring belt, umbrella cloth, protective cloth etc. Miscellaneous: Sausage casing, cellophane, feminine hygiene, beach and sports wear, fire fabrics, (Viscose + cotton) this blend is used for reducing cost, (Viscose + polyester) this blend is used for comfort, strength and absorbency.

48. Acetate Rayon Acetate Rayon is modified regenerated cellulose fiber where at least 92% of the hydroxyl groups are acetylated. Cotton linters or wood pulp sheets are used for manufacturing “Acetate Rayon”. Cellulose acetate is manufactured by dissolving cellulose and then regenerating into cellulose acetate: (primary or secondary). Alcohol + Acid --> Ester If the cellulose is treated with acetic acid under certain conditions the free hydroxyl groups of cellulose are converted into ester groups.   First prepared in 1865 by heating cotton with acetic anhydride at 130-140 degree centigrade. In 1894, Cross and Bevan developed a more practical approach, in which acetylation was carried at atmospheric pressure using sulphuric acid or zinc chloride as catalyst. Can be produced as primary acetate (cellulose triacetate) or secondary acetate or acetate rayon.

49. Basic Principles of Acetate   Fiber Production   Acetate is derived from cellulose by reacting purified cellulose from wood pulp with acetic acid and acetic anhydride in the presence of sulfuric acid. It is then put through a controlled, partial hydrolysis to remove the sulfate and a sufficient number of acetate groups to give the product the desired properties. The anhydroglucose unit, is the fundamental repeating structure of cellulose, has three hydroxyl groups which can react to form acetate esters. The most common form of cellulose acetate fiber has an acetate group on approximately two of every three hydroxyls. This cellulose diacetate is known as secondary acetate, or simply as “acetate”. After it is formed, cellulose acetate is dissolved in acetone for extrusion. As the filaments emerge from the spinneret, the solvent is evaporated in warm air (dry spinning), producing fine filaments of cellulose acetate.

50. Primary Acetate Completely acetylated cellulose in which all three hydroxyl groups of glucose unit in cellulose molecules are acetylated. It was obtained as tough solid and is soluble in toxic and expensive solvents like chloroform. Secondary acetate Discovered in 1906 that triacetate could be partially hydrolyzed of i.e. by removing some of acetate group of triacetate and reconverting into hydroxyl group. It was formed by complete acetylation and subsequent partial hydrolysis and is called secondary acetate. It is obtained from primary acetate. It is soluble in relatively cheap and non toxic solvent like acetone.

51. Raw Materials Cotton linters or wood pulp Chemicals: 1. Glacial Acetic Acid 2. Acetic Anhydride Catalyst: Sulphuric Acid or Zinc Chloride Manufacturing Process Manufacturing of acetate rayon takes place in four stages: Acetylation process Hydrolysis Preparation of Dope solution Spinning

52. Acetylation process Purified cotton linters/purified waste cotton/ bleached pulp sheets are fed to the reactor. A mixture of acetic anhydride, glacial acetic acid and small amount of conc. H₂SO₄ are added to reactor. The reactor is sealed after adding the mixture of chemicals and cotton linters. A stirrer is used to mix the ingredients thoroughly. Acetylation reaction is an exothermic reaction. The heat liberated during acetylation is removed by circulating cold water through jacket fitted outside the reactor. The acetylation reaction is completed in 7-8 hrs at 25-30ºC. Triacetate is formed at this stage. Hydrolysis (Partial Deacetylation ) Triacetate is stored for ageing. Then acetic acid, water and sulphuric acid are added and allowed to stand for 10-20 hrs. During this period, partial conversion of acetate groups to hydroxyl groups takes place. Careful control is necessary during hydrolysis. The mixture is then diluted with water and stirred constantly. The secondary acetate separates in the form of white flakes. The water is removed and then reaction vessel is filled with fresh water. The water is changed several times to obtain all the secondary acetate formed. The white flakes are centrifuged and excess of water is removed. The flakes are then dried.

53. Preparation of dope solution Dried flakes are dissolved in acetone and a viscous solution is formed, this viscous solution is known as “ Dope solution”. The dried acetate flakes are mixed with three times their weight of acetone in the enclosed tank provided with powerful stirrer. The acetate is dissolved slowly in the solvent. It takes about 24 hours for complete dissolution to give a thick (viscous) clear liquid. The solution is filtered. The spinning solution contains 25-35% of secondary acetate.

54. Spinning A dope is fed from the feed tank and dope is filtered through a filter to avoid trouble due to solid particles interfering with smooth flow of dope through jets. A metering pump ensures a constant flow of dope to spinneret. The spinneret consists of metal plate through which number of small holes are made. The number of holes in the jet determines the number of filaments in the yarn. As the dope is squeezed out of jets, it emerges in filaments form into spinning cabinet. The filaments travel vertically down towards a feed roller from which it is guided on to bobbin. A slight twist is inserted as it is taken up. Take up speed is normally between 200 and 400 meter per minute. A slight stretch is also imparted to yarn to give some degree or orientation to the molecules. The stretched yarn become stronger than unstretched yarns due to orientation of molecules.

55. The diameter of filaments depend on following three factors: Rate at which dope is fed by pump Diameter of jets Rate of stretching filaments The hot air at 100℃ is fed from the bottom of cabinet. The hot air evaporates all acetone in the dope from the jets. The acetone is withdrawn from the top of cabinet and taken away to recovery plant. The acetone air mixture is scrubbed in water towers. The efficient recovery of acetone and acetic acid is essential for economic manufacture of Acetate Rayon. Important factors in the spinning process are: Temperature Moisture Content Velocity of Air The filaments are collected on spinning bobbin. Filaments are available from 45-600 denier. Staple fibers are 3-20 denier and cut into 1.5’’, 2’’, 2.5’’, 3’’, 3.5’’ and 5’’.

56. Difference between triacetate and diacetate fiber Triacetate/Primary Acetate Fiber Diacetate /Secondary Acetate Fiber Complete hydrolysis of cellulose is occurred. Partial hydrolysis of cellulose is occurred. All –OH group is replaced by acetate group. All –OH group is not replaced by acetate group. Dissolved in chloroform. Dissolved in acetone. Good color fastness. Color fastness is not good. Higher strength and elasticity. Comparatively lower strength and elasticity. Good heat setting property. Heat setting property is somewhat poor.

57. Properties of Acetate Fiber Tensile strength In dry state the tenacity is 1.1-1.3 g/denier. It does not lose strength as viscose when it is wet. The tensile strength of acetate is 18000-22000 lb /square inch. Elongation Elongation is 23-30% when dry and 35-45% when wet. Elastic recovery At 4% extension , acetate has recovery 48-65%. When stretched further, the fiber undergoes plastic flow and becomes permanently deformed and does not return to its original position. Luster Very bright in luster. Handle Soft in handle. Drape Very satisfactory quality. Melting point It is a thermoplastic material. It becomes sticky at 190ºC and at 205ºC soften enough to deform under pressure. It melts at 232ºC.

58. Effect of Moisture In acetate the hydroxyl groups have been replaced by acetate groups. The inherent attraction of acetate for water molecules is less than that of viscose. Acetate does not absorb as much water as the viscose. The standard moisture regain is 6.5%. Effect of High temperature At 120ºC, it retains much of its original strength. Effect of age Slight decline in tensile strength over prolonged period of time Effect of sunlight Deterioration after prolonged exposure resulting in some loss of strength. Retention of tenacity is improved by addition of certain color pigments. Effect of acids Dilute acids does not attack acetate but fibers are damaged by strong acids. Effect of alkalis Strong alkali can cause saponification. The acetate groups are replaced by hydroxyl groups and cellulose acetate is gradually changed to regenerated cellulose.

59. Biological Resistance Acetate is highly resistant to mildew, moulds and bacteria. Shrinkage Acetate has good dimensional stability and retain its shape in washing and laundering. Heat Conductivity It acts as insulator. Solubility Soluble in Acetone, Methyl Ethyl Ketone. Cleaning and washing Soaps and mild detergents can be used safely in warm water. The garments should not be rubbed vigorously and warm water must be squeezed. Effect of strong oxidizing agent/ Bleaching Acetate is attacked by strong oxidizing agents but not affected by normal bleaching solutions the chemical properties depend on degree to which acetate groups have replaced hydroxyl groups in cellulose molecule.

60. Acetate Fiber Blends a. Acetate and Wool b. Acetate and Viscose Rayon Uses of Acetate fiber Apparel:  Blouses, linings, wedding and party dress, home furnishings, draperies, lingerie, garment linings and certain specialty fabrics. Triacetate is used in sportswear, tricot fabrics, and in garments where pleats and pleat retention is important as well as in certain specialty fabrics. Household uses: Curtains, Bed sheets, Pillow covers etc. Industrial Uses:  Cigarette filters.

61. LYOCELL THE NEW AGE FIBRE 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. Lenzing AG. is currently (2013) the only major producer of lyocell fibres. Tencel is the brand name of Lyocell .

62. 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.

63. 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 in large capacities 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

64. 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.

65. 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.

66. 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.

67. 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.

68. Solvent Recovery After spinning and drying process, dilute solution is taken passed through the evaporator where water is removed and amine oxide solvent is fed back to the Dissolving process.

69. 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

70. 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.

71. 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.

72. 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

73. 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