Post on 11-Jan-2017
CHAPTER FOUR
LECTURE 4 ON
Man- Made Fiber Formation and Regenerated Fibers.
BAHIR DAR UNIVERSITY (EiTEX)BAHIR DAR UNIVERSITY (EiTEX)
By: Bademaw Abate(Lecturer)
INTRODUCTION INTRODUCTION INTRODUCTION INTRODUCTION � Textile fibers are made by man starting from various kinds ofraw
materials. Thestarting raw materials for fiber making can benatural and
synthetic polymers.
� Accordingly man- made fibers are classified in toregenerated and
synthetic.
Basic principle in fiber manufacturingBasic principle in fiber manufacturing
� Conversion of the fiber-forming substance into a fluid solution or melting
� Extrusion of the fluid throughspinnerets
� Solidification of the extrudedfilaments
� The technology of man made fiber manufacturing --- SPINNING
� A spinneret (perforated plate) may have fromone to several hundred holes.
Monofilament: when the spinneret has only single hole
Multi-filament: the bunch of filaments from a multi-hole spinneret.
TECHNOLGY OF MAN MADE FIBERSTECHNOLGY OF MAN MADE FIBERSTECHNOLGY OF MAN MADE FIBERSTECHNOLGY OF MAN MADE FIBERS
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� Spinneret hole may be circular or some other shape based on requirement. This
enables production of filaments having differentcross-section.
SPINNING METHODSMELT SPINNING
� In melt spinning, the fiber-forming substance is melted forextrusion through
the spinneret and then directly solidified by cooling in an air stream.
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KeyKeyKeyKey requirementsrequirementsrequirementsrequirements:::: EaseEaseEaseEase ofofofof melting,melting,melting,melting, meltmeltmeltmelt stabilitystabilitystabilitystability
andandandand optimumoptimumoptimumoptimum meltmeltmeltmelt viscosityviscosityviscosityviscosity
Examples: Nylon, Polyester
Cont..
SOLUTION SPINNING
� In solution spinning the fiber forming polymer is dissolvedin a suitable solvent
for extrusion through a spinnerette.
� Themajorsolutionspinningoperationsaredry spinning andwet spinning.
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� Themajorsolutionspinningoperationsaredry spinning andwet spinning.
� In dry spinning the polymer solution is extruded into a stream of warm air, which
evaporates the volatile solvent and solidifies the filaments.
� In wet spinning the polymer solution is extruded into a bath containing chemicals,
which neutralize the solvent and coagulate (solidify) the filaments.
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KeyKeyKeyKey requirementsrequirementsrequirementsrequirements:::: PolymerPolymerPolymerPolymer ssssolubilityolubilityolubilityolubility &&&& solutionsolutionsolutionsolution viscosityviscosityviscosityviscosity
DRY SPINNINGDRY SPINNINGDRY SPINNINGDRY SPINNING WET SPINNINGWET SPINNINGWET SPINNINGWET SPINNING
Example: Viscose rayonExamples: Acetate, Acrylic
Flow chart of MMF production:
1. Manufacture of the fibre forming polymer.
2. Spinning ( extrusion through spinneret)
3. Stretching/Drawing ( improving strength and crystallinity)
4. Texturing/Crimping ( developing natural fibre properties)
5. Heat setting( made dimensionally stable)
6. Cutting: According to requirements.
REGENERATED FIBERS
� The raw materials used for the production of regenerated fibers are
natural polymers.
� Nature has done the work of preparing something that can be
converted into fiber.
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� The only involvement of man is converting this material in to a
suitable fiber.
� Most widely used regenerated fibers areviscose rayon andacetate.
VISCOSE RAYON
� The raw material for viscose rayon production iscellulose
obtained fromwood pulp.
� Viscose rayon fiber is produced bywet spinning technology.
� The firs step is preparation of aspinnable solution of cellulose
knownasviscose.knownasviscose.
� Next wet spinning is carried out which involvesextrusion through
spinnerets &coagulation.
� The coagulation bath which consistsacids and salts responsible
for neutralization and regeneration of the original cellulose as
continuous filaments.
Manufacturing Process of Viscose Rayon
� The chemical structure of viscose is comparable to cotton.
� Thecellulose molecules are muchshorter than those of cotton
� Their organization in the fiber is also different (low degree of
VISCOSE RAYON: FIBER STRUCTURE AND PROPERTY
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crystallinity)
� The fiber cross-section is serrated and longitudinally striations are
observed along the length of the fiber.
DP = 250 -350
�Thetenacity is lower than cotton and muchlower wet strength
� Theelongation at break ishigher than cotton
� Viscosewrinkles easily and hashigh moisture regain than cotton
� Low tendency of static charge build up
PARAMETER CHARCTERISTIC VALUEPARAMETER CHARCTERISTIC VALUE
Tenacity 2-3
Elongation 10 – 20%
Elastic recovery Between silk and cotton
Specific gravity 1.51
Heat Conductivity Moderate
Moisture regain 11- 13%
uses of Viscose Rayon�Rayon typically has an elevated luster quality giving it a brilliant gloss
�Mainly, Rayon fibres are used inapparel industrysuch as Aloha shirts, blouses, dresses, Jackets, Lingerie, scarves, suits, ties, hats and socks…,
� Some rayon fibres are for filling in Zippo lighters, furnishings including bedspreads, bed sheets, blankets, window covers, upholstery and slipcovers..,
� For industrial purposes such as medical surgery products, non-woven items, tire cord and some other uses like diapers, towels, feminine hygiene products..,
CELLULOSE ACETATE FIBERS
� Acetate rayon is the generic name for cellulose acetate fiber in at least 74%
of the hydroxyl groups of cellulose are acetylated.
� The raw material for the production of cellulose acetate fibers is cotton
linters/wood pulp.
� The hydroxyl groups of cellulose are replaced by acetate groups.� The hydroxyl groups of cellulose are replaced by acetate groups.
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(CH3COO -)
ACETATE FIBER MANUFACTURING
� Cotton Purification: Cotton linters are first purified to remove
impurities.
� Pretreatment: Stepping in glacial acetic acid to make reactive for
acetylation
� Acetylation: Hydroxyls (-OH) in cellulose are replaced by acetyl � Acetylation: Hydroxyls (-OH) in cellulose are replaced by acetyl
groups (CH3COO -)
� Treatment with anexcess of glacial acetic acid and acetic anhydride
� Sulphuric acid dissolved in acetic acid is added to complete
acetylation.
� All the cellulose is converted intocellulose triacetate
� The cellulose triacetate thus formed is known asPrimary Acetate15
Manufacturing Process of Cellulose Acetate
� Preparation of Dope: The blended secondary acetate is mixed three times its
weight of acetone in a closed vessel. Acetone dissolves it slowly.
� The solution of cellulose acetate in acetone is thespinning dope. Dope is
filtered, dearated and then run into feed tank.
ACETATE FIBER MANUFACTURING
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Spinning� The method of spinning used is dry sinning. The dope is extruded through the
spinneret and the acetone solvent is gradually removed by means of warm air.
� Post spinning operations as usual and as per requirement.
ACETATE FIBER: MAJOR FEATURES
� Presence of bulky side chain groups leading to limited closepacking
� Presence of hydrophobic groups lower moisture characteristics
� Low tenacity [1.4gpd (dry) and 0.9gpd (wet)]
� High elongation [30% (dry) and 40% (wet)]
� Elasticrecoverygoodat low elongation
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� Elasticrecoverygoodat low elongation
� Moderate moisture regain [6.5%]
� Moderate density [specific gravity 1.32]
� Acetate Rayon is more sensitive to heat. It begins to weaken at 93 deg C. At 175
deg C it becomes sticky and melts at 260 deg C. Like nylon and polyester it is
thermoplastic.
� Acetate rayon is soluble in acetone.
Uses of Acetate fiber
�Acetate is used in dresses, blouses, foundation
garments, lingerie, garment linings, some household
furnishings, and certain specialty fabrics.
�Triacetate is used in sportswear, tricot fabrics, and in �Triacetate is used in sportswear, tricot fabrics, and in
garments where pleats and pleat retention is
important, as well as in certain specialty fabrics.
Thank You