chemisty of

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CHEMISTY OFTEXTILE

FIBERS AND

THEIRPROPERTIES


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Textile and Clothing Technology.

@ BCCT Rathmalana, Sri Lanka.

Nalaka Sampath

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Introduction

In textile industry, chemical science is taken a huge part of the producing of

fibres, yarns and other fields like chemical finishing.

In the textile industry, from fibres to final dress, chemistry applicationsare used in various ways as they needed.In this section mostly discus about theapplication of the chemical science on textile fibres. And how they produce out.

How to make synthetic fibres and regenerated fibres and how they used tomake a fine yarn are the things we discus here.

What is a polymer?

The polymer is large molecule, made out from onerepeating unit, called monomer. The monomer is like a link in a chain. Itsrepeating along the polymer like in a chain. These monomers connected to eachother monomers by a chemical bond, called covalent bonds.

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Contend

Classification fibre... ...011. Regenerated fibres.......02

1) protein fibres.02a) milk fibres...02b) wool fibres..03

02)Cellulose fibre..........04a) Cellulose acetate fibre....04b)Art silk..04d) Bamboo...04e) Lyocell......04f) Rayon.......04

02. synthetic fibres...06 01)Addition polymerization..07 02) Condensation polymerization....................................................08

Synthetic fibre 02..10a) Nylon 6-6....11b) Nylon 6-10..12c)Aramid...................................................................................13d) Polyacrylonitrile...14f) Olefin.....15

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Classification of textile fibres.

Under the textile fibre, the applications of chemical science can be discussed intwo ways.

1. Regenerated fibre.;-In the textile industry regenerated fibres are made out

for create fine fibres from protein and cellulose.

2. Synthetic fibre.;-This fibre format is made from polymer by a process

called polymerization. Polymers are formed by hydro carbonatesand they used to produce filaments for manufacture the yarns.

These two classification will be discussed due course.

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01. Regenerated fibre

Regenerated fibre can divide in to two sections.1. Protein fibers.2. Cellulose fibres.

1. Protein fibres.

a. Milk fibre.

The raw material of this fiber production is naturally available milk. The proteinspinning fluid is made out from new bio-engineering technology to make itsuitable for wet spinning process.

The fabrics are made from this type of fibres are popular ashealthy for skin and comfortable to wear. These fibres can be spun purely orblend with other fibre type like silk.

Process of milk fibre production.

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b. Wool fibre

Most of the animal fibers are protein fibers. Such as silk and wool. Inthis production of fiber forming, there should be a chemical treat to do this better.Some of the chemical reactions take place during the process of forming purefibres.

When we are using wool to make a yarn wehave to clean them. In a wool mill there are so many chemicals added to cleanthe wools. First it uses sodium carbonate as a soap to wash out greases. Then itremoves vegetable matters by using sulfuric acid.

Type of fibres

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2. Cellulose fibres.

Naturally available cellulose cannot be used to form a fibre.There is process called regenerating to make them used in industry. Actuallyregenerating is anther type of polymerizing. To do this task first its madedissolving pulp. This is also known as dissolving cellulose. This pulp is wood pulpwhich contains high concentration of cellulose. Concentration of the cellulose inthis pulp is depended on the purpose of the fibre type which is going to make out.

The cellulose is dissolved in an organic solvent and processedto regenerate the cellulose fibres in different forms.

The 90-92 % cellulose content sulfite pulps are used mostlyto make textiles like rayon and cellophane. The 96-% cellulose content sulfate pulps areused to make rayon yarn for industrial products.

Cellulose polymer. Cellulose monomer.

When cellulose is regenerated there would be many types cellulose fibres.

a) Cellulose acetate

b) Art silk

c) Bamboo

d) Lyocell

e) Rayon

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a) Cellulose acetate

This fiber format is the acetate ester of the cellulose.Cellulose acetate is used as a film based on photography

b)Art silkArt silk is known as artificial silk also. The first successful artificial

silks were developed in the 1890s of cellulose fiber and marketed as art silk.

c) BambooThis is also a cellulose fibre extracted from natural bamboo. The pulp

which is used to make fibres is made out of bamboo plants.The process to make viscose or rayon fibre from bamboo is the same processused to produce viscose/rayon from any other plant source.

d) LyocellLyocell is a trade name for the fibres made from dissolving pulp of

eucalyptus trees. The wood pulp is dissolved in N-methylmorpholine N-oxide,creating a solution called "dope," which is then pushed through a spinneret to

form the individual fibres.

e) RayonRayon is known by the names viscose rayon and art silk in

the textile industry. Rayon is made out from cellulose after it is treated withcarbon disulfide and sodium hydroxide. So it can be named as semi syntheticfibre.

The formation of rayon polymer.

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02. Synthetic fibres.

Synthetic fibres are man made fibres, which are entirely made out from chemicalresources such as petroleum, coal.. act. Synthetic fibres are continuousfilaments. In a synthetic fibre there is polymer which its structure is based on.These polymers are mostly hydro-carbonated polymers.

To form a polymer, there is one repeating unit. This repeatingunit is may made out from one or more molecule. The polymer type which isfinally taken out from process called polymerization, is depended on the type of itis polymerized and how many molecules are in a monomer.

There is two type of polymerizing and they discus below.

i) Addition polymerization

ii) Step-growth polymerization.

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Addition polymerization:-An addition reaction takes place during the addition

polymerizing. There is many monomers bond together via rearrangement ofbonds to make this kind of polymers.

Simply it can be described as monomers double or triple

bonds are opened up to form a continuous chain of carbon.The general reaction can be represented as :

nR-C=C-R'

catalyst

-(-

R|C -

R'|C -)n-

Ex;-

Propylene polymerization.

Ethylene polymerization.

Vinyl chloride polymerization.

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Condensation polymerization.

There are two types of polymerizing processes under this classification.Condensation and step-growth polymerization. Even though these polymerizingconcepts are difference, they take into a one classification because ofcondensation polymerizations mechanism corresponds to step-growthpolymerization.

Step-growth polymerization typically takes place betweenmonomers containing functional groups that react in high yield to form newfunctionalities. When two monomers react to form a polymer, there is small

molecules are eliminated during the reaction, such as water molecule.

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Synthetic fibres.

Synthetic fibres are totally made out of chemicalcompounds known as polymers. These polymers polymerizing concepts aremainly affected to the fibre type which its going to produce out. (Thepolymerizing types have discussed above)

Synthetic fibres account for about half of all fibre usage, withapplications in every field of fibre and textile technology.

In this section mainly discus about the synthetic textile fibres, such as;

a) Nylon 6-6.b) Nylon 6-10.c) Aramid.d) Polyacrylonitrile.e) Olefin.

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a) Nylon 6 -6.

These types of fibres are produced by using amide groups.These amide groups are polymerized and they called as polyamide.

There many types of fibres made out from polyamide. Most known polyamidefibre is nylon. Nylon also has many of varieties.

We discus here about nylon 6-6.As its name there are 12 carbon atoms

given by hexamethylenediamine and adipic acid, to produce nylon 6-6. Thesetwo molecules are combined with water in a reactor, then its formed nylon

salt. After removing excess water its sent to the reaction vessel to produce acontinues nylon filament. Molten nylon 6-6 goes through a process calledspinning to produce those filaments. Then its cooled.

Properties of nylon 6-6.;-

Much greater stiffness and tensile strength.

Lower water absorption.

Improved heat distortion temperature.

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b) Nylon 6-10

This type also based on polyamide. (It hasdescribed above) Nylon 6-10 is formed at the interface between the two

solutions. These two solutions are 1,6-diaminohexane and sebacoyl chloride.

The spinning process is as same as the spinning process of nylon6-6. its used melt spinning method for this task.

Properties of nylon 6-10

Lower brittle temperature than Nylon 6 or Nylon 6-6.

Lower water absorption than Nylon 6 or Nylon 6-6 (4% atsaturation).

Stronger than Nylon 11, Nylon 12 or Nylon 6-12.

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c) Aramid.

Aramid fibre is a product of Aramid polymers. Those are prepared by thereaction between an amine group and a carboxylic acid halide group.They areused in aerospace, military applications and many technical applicationsbecause of their high strength.

Most known aramids are Kevlar and Conex.

KevlarThis is a trade mark of the synthetic fibre, para-aramid.

During the production process of Kevlar, condensation reaction takes placealone the process. Terephthaloyl chloride and 1,4-phenylene-diamine are thechemicals used chemicals to produce this.

Properties of Aramid.

Usually yellow in appearance

Low density

High strength

Good impact resistance

Good chemical resistance

Good resistance to thermal degradation

Some grades of aramid fibre can degrade when exposed to

ultraviolet light

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d) polyacrylonitrile .

Polyacrylonitrile can be found in two types o fibres. Homo-polyacrylonitrile and co-polyacrylonitrile. These types of fibres are used invarious ways according to their qualities.

Copolymer of polyacrylonitrile fibres are mostly used to make

socks and sweaters(in knitted fabrics), as well as outdoor products such astents and other things. Most known trade name for co-polyacrylonitrile is Orlon.

Homopolymers of polyacrylonitrile fibers is used tohot gas filtration systems, outdoor tents, and for yachts.

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e) Olefin fiber. This fibre is made from alkenes.

There are two type of olefin fibres whichis depended on its polymerization process. Polyethylene and polypropylene.

In textile industry, there is various usage of this kind of fibres such asin vehicle interiors, clothing and other fields like rope manufacturing.

Polyethylene for ropes.When producing of olefin fibres Polymerization of

propylene and ethylene gases, controlled with special catalysts.

Properties of olefin

Low dielectric loss

Low water absorption

Excellent dimensional stability

High heat resistance

Good chemical resistance

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