chemistry of textile fibres & their properties

CHEMISTRY OF TEXTILE FIBRES & THEIR PROPERTIES

M.P.ASIRI VIDULNIC# 902451218V

Contents

Introduction.................................................................................................................................................3

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Classification of Polymers............................................................................................................................4

Condensation Polymers...............................................................................................................................5

Classification of Fibres.................................................................................................................................6

Types of Intermolecular Attractive Forces...................................................................................................7

Cotton......................................................................................................................................................8-7

Silk and Wool Proteins...........................................................................................................................10-9

Viscose Rayon........................................................................................................................................10-11

Cellulose Acetate...................................................................................................................................12-13

Polyester............................................................................................................................................153-14

nylons..........................................................................................................................................................14

Nylon 6.6.................................................................................................................................................15

Nylon 6.8.................................................................................................................................................16

Nylon 6.10.............................................................................................................................................17

Polyvinyl chloride......................................................................................................................................18

Polypropylene......................................................................................................................................19-20

Polystyrene................................................................................................................................................20

Polyacrylonitrile...................................................................................................................................21-22

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Introduction

All textile fibres (natural and man-made) are made out of Polymers. A polymer is a chemical species of very high molecular weight that is made up of many repeating units of low molecular weight. The compound used to make the polymer is called a Monomer. The smallest unit which reacts again and again with itself to give the macro molecule is called the Repeating Unit. The process where by a large number of monomers combine together to form a macro molecule is called Polymerization.

For example if we take Ethylene

Monomer

Repeating Unit

Polymer (Polythene)

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Classification of Polymers

Polymers can be classified in to two considering the type of reaction used for polymerization.

1. Addition Polymers2. Condensation Polymers

Addition Polymers

An addition polymer is a polymer formed by linking together many molecules by addition reactions. Several monomers add on to each other to form a polymer without eliminating any molecules. The monomers must have multiple bonds that will undergo addition reactions. In addition reactions the π-bonds in the monomer brakes and forms σ-bonds with other molecules.

For example if we take vinyl chloride

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Condensation Polymers

A condensation polymer is a polymer formed by linking together many molecules by condensation reaction. Condensation reaction occurs in the functional groups of the monomers. In this reaction a small molecule such as H2O or HCl is eliminated and a new bond is formed with other monomers.

Example for a condensation polymer

-H2O

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Coconut

Natural Fibres

Organic Inorganic

Vegetable Animal

Seed Stem Leaf Fruit

Wool Hair Silk

Quarts

CottonKapok

rts

FlaxHem

pJuteRamie

SisalManila

Pineapple

AlpacaCamelGoat

RabbitHorse

Textile Fibres

Man-made Fibres

Natural Polymers

Synthetics

Cellulose Rayon

Cellulose Esters

Protein Polyamides

Polyester Polypropylene

Polyvinyl

Classification of Fibres

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Types of Intermolecular Attractive Forces

Cotton

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Cotton is the most important fibre to the textile industry. It is also natures most abundant polymer. Fabric from cotton are comfortable to wear and they can be dyed in wide range of colours. Each cotton is an elongated cell. The mature fibre is actually a dead hollow cell wall composed of almost entirely (90%) of cellulose. The structure of the cellulose is as below.

Monomer

Repeating unit

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Polymer

Cellulose is made up condensation polymerization of glucose. The bonds which are present in this polymer are Covalent bond, van der waal forces and dipolar-dipolar attraction. The present of oxygen and hydrogen also forms hydrogen bonds.

Cotton Fibre Properties

Moisture regain/ absorption - high moisture regain, absorb water molecules into amorphous region due to OH hydrophilic groups. Cotton has a regain about 8.5%. cotton is stronger when wet than dry.

Resistance to micro organism – cotton supports mildew or bacteria formation than nylon fibre.

Resistance to acid – weakened and destroys by acids.Concentrated cold or diluted mineral acids like H2SO4 will damage cotton.

Resistance to heat – Cotton has the ability to withstand moderate heat. But extreme heat will cause cotton goods burnt.

Comfort – very comfort to wear than nylon because of its moisture regain property. Elasticity – relatively inelastic due to crystalline and hydrogen bonds. Resistance to alkaline – cotton has a resistance to alkaline. Alkali does not harm cotton

fibre.. Strong alkali solution (NaOH) improves the qualities of cotton fibre. The treatment of cotton fibre with sodium hydroxide & lustrous

Durability – durable and unaffected by laundering.

Silk and Wool Proteins

Silk and Wool is a natural protein fibre which consist of Amino Acids

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H H O H N C C OH R

H H O N C C R

H H O N C C R

H H O N C C R

H H O N C C R n

H H O N C C R

H H O N C C R

Monomer

Repeating Unit

Polymer

Proteins are made up of condensation polymerization Amino Acids. The bonds which are present in this polymer are Covalent bond, van der waal forces and dipolar-dipolar attractions. The present of nitrogen and hydrogen also forms hydrogen bonds.

Wool Fibre Properties

Length: fine wool are about 1 ½ - 5 inches. Long wools are about 5-15 inches.

Appearance: wool is a roughly oval in cross-section. Tensile strength: wool has a tenacity of 1-1.7 g/denier.

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Elongation: wool has an elongation at break of 25-35% under standard conditions.

Elasticity: wool is unusually resilience. It has an elastic recovery of 99%.

Effect of moisture: wool absorbs moisture to a great extent. Moisture regain is about 16-18%.

Silk Fibre Properties

Length: silk filament may be as much as one mile in length. Tensile strength: strong fibre. Tenacity: 3.5-5 g/denier Elongation: elongation at break 20-25% Elasticity: elastic recovery of silk is not good as wool, but better than

cotton. Effects of moisture: like wool, silk absorbs moisture. Moisture regain

is 11%

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Viscose Rayon

Viscous Rayon is produced by cellulose which comes from wood. Cellulose is purified and is treated with caustic soda which is converted into alkali cellulose. It is then treated with carbon disulfide which converts it into sodium cellulose Xanthate. In this polymer covalent bond, van der waal forces and ironic bonds are present.

NaOH +

Sodium Cellulose Xanthate CS2

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Viscose Rayon Fibre Properties

Moisture Absorption:It absorbs more moisture than cotton. Moisture Content of Coton is 6% at 70 deg F and 65% RH, and for Viscose Rayon it is 13% under the same conditions.

Tensile Strength :The Tensile Strength of the fibre is less when the fibre is wet than when dry. It is 1.5-2.4 in the dry state and 0.7-1.2 in the wet state. For high tenacity variety the values are 3-4.6 and 1.9 to 3.0

Elasticity:The elasticity of Viscose Rayon is less than 2-3%. This is very important in handling viscose yarns during weaving, stentering etc when sudden tensions are applied.

Elongation at Break:Ordinary Viscose rayon has 15-30% elongation at break, whule high tenacity rayon has only 9-17% elongation at break.

Density:The density of Viscose rayon is 1.53 g/cc. Rayon filaments are available in three densities: 1.5, 3.0 and 4.5

Action of Heat and Light:At 300 deg For more, VR loses its strength and begins to decompose at 350-400 deg F. Prolonged exposure to sunlight also weakens the fibre due to moisture and ultraviolet light of the sunlight.

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Cellulose Acetate

Cellulose acetate polymer is formed with covalent bonds and van der waal forces.

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Cellulose Acetate Fibre Properties

Hand: soft, smooth, dry, crisp, resilient Comfort: breathes, wicks, dries quickly, no static cling Drape: linings move with the body linings conform to the garment Color: deep brilliant shades with atmospheric dyeing meet

colorfastness requirements Luster: light reflection creates a signature appearance Performance: colorfast to perspiration staining, colorfast to dry

cleaning, air and vapor permeable Tenacity: weak fiber with breaking tenacity of 1.2 to 1.4 g/denier;

rapidly loses strength when wet; must be dry cleaned. Abrasion: poor resistance

Heat retention: poor thermal retention; no allergenic potential (hypoallergenic)

Dye ability: (two methods) cross-dying method where yarns of one fiber and those of another fiber are woven into a fabric in a desired pattern; solution-dying method provides excellent color fastness under the effects of sunlight, perspiration, air contaminants and washing [1,2]

Polyester

Polyesters are made by a condensation reaction taking place between small molecules. The linkage of the molecules occurs through the formation of ester groups. An ester is formed by reaction acid with an alcohol.

Monomer

Repeating Unit

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-H2O

Polymer

The bonds which are present in this polymer are Covalent bond, van der waal forces and dipolar-dipolar attraction. The present of oxygen and hydrogen also forms hydrogen bonds.

Polyester Fibre Properties Very strong. So garments made from polyester fibres last longer than the

ones made from natural fibres Very resistant to wrinkles. Polyester garments retain their crease Not a good absorbent of water. Therefore polyester clothes dry faster Highly abrasion and moth resistant Resistant to ordinary chemicals and biological agents

NylonsCondensation polymerization of di-carboxilic acid or di-carbonile

chloride with di-amine gives Polyamide. Polyamides are of different types.

Nylon Fibre Properties

1. Length: Length of nylon filament is unlimited and staple fibre lengths are controllable.

2. Fineness: Nylon fibre fineness is also controllable.3. X-sectional shape: Normally round shape but the cross sectional shape

could be changed.4. Strength of nylon fibre is very high. Its tenacity varies from 4.6 to 5.8

g/den.5. Extensibility: Nylon is highly extensible fibers. Extension at break is 30%

but the problem is poor recovery form extension. For that reason it is not used as sewing thread for garment.

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6. Resiliency: It has good resiliency property. Nylon fibers, yarn or fabric does not crease easily. For that reason it is widely used for the pile fabric production. For instance velvet, carpet etc.

7. Frictional Resistance: Nylon fibre shows good frictional resistance. Due to high strength and good frictional resistance property it is widely used for rope.

Nylon 6.6

Monomer (hexan-1,6-dioc acid + 1,6-diamionhexane)

Repeating Unit

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-n H2O

Polymer

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Nylon 6.8

Monomer (octan-1,8-dioc acid + 1,6-diaminohexane )

Repeating unit

Polymer

The bonds which are present in Nylon Polymers are Covalent bond, van der waal forces and dipolar-dipolar attraction. The present of nitrogen and hydrogen also forms hydrogen bonds which makes it a very strong polymer.

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n

+

Nylon 6.10

Monomer (Sebacyl chloride + 1,6-diaminohexane)

Repeating Unit

Polymer

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+

Polyvinyl chloride

Addition polymerization of Vinyl Chloride gives Polyvinyl chloride.

Monomer

Repeating Unit

Polymer

Covalent bonds are found to be present in the above polymer. Intermolecular attractive forces are van dal waal forces and the melting points and boiling points are low due to non existence of other intermolecular attractions.

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n

Polypropylene

Addition polymerization of propylene gives Polypropylene

Monomer

Repeating Unit

Polymer


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n

Polypropylene Fibre Properties

Weight: Polypropylene is a light weight material. Tensile strength: Its tensile strength is high. It shows strong

resistance towards stress and cracking. Shape: Polypropylene is crystalline in nature and possesses a regular

geometrical shape. Insulation: It acts as an excellent insulating substance. Moisture Absorption: Polypropylene does not get affected by

moisture as its moisture absorption is very low. Melting Point: Melting point of polypropylene is 160°C. Therefore,

unlike other polymers (polyethylene, polypropylene), it is capable of being operational even at a very high temperature.

Corrosion: Polypropylene remains unaffected by chemicals like alkaline substances, acids, de-greasing agents, electrolytic attacks, etc. However, its resistance towards aromatic or aliphatic hydrocarbons, chlorinated solvents and ultraviolet radiation is not very strong.

Other Useful Properties: It is a non poisonous material. It does not get stained very easily. It can be easily fabricated. It can retain its stiffness and flexibility at very high temperatures.

Polystyrene

Addition polymerization of styrene gives Polystyrene.

Monomer

Repeating Unit

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Polymer


Polystyrene Fibre Properties

Density - 1.05 g/cc Dielectric constant - 2.4 to 2.7 Thermal conductivity - 0.08 W/(m.K) Young's modulus - 3000 to 3600 Mpa Tensile strength - 46 to 60 Mpa Melting point - 240 ºC Water absorption - 0.03 to 0.1

Polyacrylonitrile

Addition polymerization of acrylonitrile gives Polyacrylonitrile.

Monomer

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n

Repeating unit

Polymer

Covalent bonds are found to be present in the above polymer. Intermolecular attractive forces are van der waal forces and the melting points and boiling points are low due to non existence of other intermolecular attractions.

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chemistry of textile fibres & their properties

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