Fiber Science By Chamal Jayasinghe [B.Sc. Engineering (Textiles)]

FiberFiberss

A thin long flexible structure In A thin long flexible structure In witch, the ratio of length to witch, the ratio of length to diameter is very high. diameter is very high.

This ratio should be at least 100: 1 This ratio should be at least 100: 1 to be considered as a fiber.to be considered as a fiber.

To spin textile yarn successfully To spin textile yarn successfully this ratio should be at least 1000: 1this ratio should be at least 1000: 1

Examples for length to diameter ratio

Fiber Type Length Diameter Length:Diameter

Cotton 1” 0.0007” 1,400:1

Wool 3” 0.001” 3,000:1

Flax 1” 0.0008” 1,200:1

Other Needful Qualities of Fibers

ThinnessFlexibilitySufficient StrengthSufficient Length

Fiber Classification

Staple and Filament FibersFibers with infinite length(long) are called filament fibers

Fibers with finite length length(relatively short length ) is called staple fibers.

Monomers → Polymers → Micro fibrils → Fibrils → Plant Cell Walls → Fibers Monomers are single structure composed of atoms.

Internal Structure of a Natural Fiber

From Monomer to From Monomer to FiberFiber

From Monomer to FiberFrom Monomer to Fiber

Looking in to Polymer Looking in to Polymer ArrangementsArrangements

Crystalline & Amorphous Regions

Crystalline & Amorphous Regions

Crystalline – Orderly arrangement of molecular chains Less internal spaces Higher strength due to better orientation Poor water penetration properties

Gives strength to the fiber Amorphous – Random arrangement of molecular More internal spaces Good water absorption Lower strength due to poor orientation of molecules.

Gives flexibility to fiber

The degree of polymerization, or DP, is usually The degree of polymerization, or DP, is usually defined as the number of monomer units in a defined as the number of monomer units in a macromolecule or polymer molecule.macromolecule or polymer molecule.

Degree of PolymerizingDegree of Polymerizing

Degree of Polymerization Degree of Polymerization with Melting Temperaturewith Melting Temperature

Nylon 6 -120Nylon 6 -120 Nylon 6,6-200Nylon 6,6-200 Polyester (PET)- 100Polyester (PET)- 100 Polyacrylonitrile > 2000Polyacrylonitrile > 2000 Viscose Rayon- 150-350Viscose Rayon- 150-350 Polynosic- 700-1100Polynosic- 700-1100 Cotton- 4000-10,000Cotton- 4000-10,000 Wool- 60,000-100,000Wool- 60,000-100,000

DP of Common FibersDP of Common Fibers

Chemical constituent of polymer(monomer) is mainly responsible for the chemical properties of textile fibers.

Physical arrangement of polymer chains in fiber structure and polymer chain length is mainly responsible for physical properties of textile fibers. 

Chemical and Physical Properties of Fibers

Physical Physical Properties of Properties of FibersFibers

The strength of textile fibers is referred to as their tenacity. It is determined by measuring the force required to rupture or break the fiber.

Sufficient tenacity is required to withstand the mechanical and chemical processing as well as make textile products which are durable.

Tenacity

General Fibre Properties

1.TenacityMolecules parallel to the longitudinal axis take their fair share of the load result in high tenacity (breaking load).

Molecules lying approximately at right angles to the longitudinal axis take little or none of the load hence result in low breaking load.

Effects of Polymer Length to Effects of Polymer Length to TenacityTenacity

Area of attraction that is greater in the long molecules than in short molecules.

Therefore fibers consist of longer molecules are stronger than fibers consist of shorter molecules.

Up to a certain point fiber strength will increase along with increasing molecular chain length.

Effects of Polymer Length to Tenacity

FinenessFineness

2.Fineness

Fibre fineness governs the end use application of fibre.Fibres used in clothing fabrics are below 5 decitex and rarely exceeds 15 decitex. .As the average number of fibres in the cross section is high, fine, staple fibres are more suitable for production regular yarns. Cloths made from fine fibres or filaments have a softer smother handleHas lower resistance to abrasion in fabrics as fine fine fibres can be easily damaged.Also being more flexible, they are liable to entangle with foreign matter and form pillings.

General Fibre Properties

Moisture AbsorptionMoisture Absorption

The ability of a fiber to absorb moisture is referred in moisture regain or moisture content.The quantity of moisture picked up varies with the relative humidity and the temperature of the atmosphere-The standard values are relative humidity of 65% and temperature of 20C. Depends on the chemical nature and physical arrangement of fiber.

Moisture Absorption

Moisture Moisture ContentContent

Moisture Content % = Moisture Content % = Moisture Moisture x 100 % x 100 % Total MassTotal Mass

Moisture RegainMoisture Regain

Moisture Regain % = Moisture Regain % = Moisture Moisture x 100 % x 100 % Dry MassDry Mass

The influence of moisture absorption of fibers.

The comfort of the wearer.The amount of shrinkage that will occur during laundering.The speed with which the textile will dry after laundering.How does the fabric or fiber neutralize static electricity

Moisture Absorption

Abrasion ResistanceAbrasion Resistance

Fabrics are abraded in use against various materials The life of a fabric is dependent on its resistance to

abrasion. Nylon has an outstanding resistance to abrasion. Abrasion resistance is decided by it’s fiber

composition yarn and fabric construction.

Abrasion Resistance

Crease Crease RecoveryRecovery

To retain a good appearance of a fabric , they must have good crease recovery from unwanted creases occur in fabric usage and laundering.

When a fiber is bent, two things can happen 1.The cross links may break and join in new positions.

When the load is removed, recovery from the crease is restricted by the new positioning of the cross links and textile will show poor crease recovery.

2.The cross links may be stretched without breaking. When the load is removed, they will tend to return the fiber to its original shape and will show good crease recovery.

Crease Recovery

Elongation & Elastic Elongation & Elastic RecoveryRecovery

The amount of extension or stretch that a fiber accepts is referred to as elongation.Elastic recovery indicates the ability of fibers to return to their original length after being stretched.

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Elongation and elastic recovery

ResiliencResiliencyy

Resiliency Resiliency

Resiliency refers to the ability of a fiber to come back to its original Resiliency refers to the ability of a fiber to come back to its original position after being creased , folded or any type of physical stress. position after being creased , folded or any type of physical stress. Good elastic recovery usually indicates good resiliencyGood elastic recovery usually indicates good resiliency Excellent resiliency is exhibited by polyester, wool and nylon fibers. Excellent resiliency is exhibited by polyester, wool and nylon fibers. Flax, rayon and cotton, on the other hand, have a low resiliencyFlax, rayon and cotton, on the other hand, have a low resiliency

LusterLuster

Luster is amount of light reflected from the surface of the fibreFine fibers provide a greater number of reflecting surfaces. Hence good lusterFibers with a uniform diameter has a greater luster. The shape of the cross section affects the degree of luster.yarns made from continuous filaments are more lustrous than those made from short fibers. Manufactured fibers can have their luster subdued by adding delustering agents.

Luster

FlexibilityFlexibility

Fibers should be flexible in order to be made into yarns and thereafter into fabrics that permit freedom of movement. Certain end uses require greater flexibility, e.g., automobile seat belts.

Flexibility

UniformityUniformity

Uniformity of fibers towards its Uniformity of fibers towards its length, ensure production of even length, ensure production of even yarns which can then form fabrics of yarns which can then form fabrics of uniform appearance and consistent uniform appearance and consistent performance.performance.

UniformityUniformity

StiffnessStiffness

Stiffness is a special property of fabric. It is the tendency of fabric to keep standing without any support. It is a key factor in the study of handle and drape of fabric.

Stiffness of the fibers and fabric structure greatly affect to this quality of the fabric.

Stiffness

Chemical Properties

Reaction with AcidsReaction with AcidsMost of the cellulose based fibers dissolves in acids.Most of the cellulose based fibers dissolves in acids.While Protein Fibers has a quite good resistance to While Protein Fibers has a quite good resistance to Acids.Acids.

Synthetic fibers has less or no reaction with acids at Synthetic fibers has less or no reaction with acids at low temperatures and low concentrations. But reacts low temperatures and low concentrations. But reacts at high temperatures and concentrations.at high temperatures and concentrations.

Most of the Protein Based fibers react with alkali.Most of the Protein Based fibers react with alkali.While Cellulosic fibers has a good resistance to While Cellulosic fibers has a good resistance to alkali.alkali.

Synthetic fibers has less or no reaction with acids Synthetic fibers has less or no reaction with acids at low temperatures and low concentrations. But at low temperatures and low concentrations. But reacts at high temperatures and concentrations.reacts at high temperatures and concentrations.

Reaction with AlkaliReaction with Alkali

It is valuable for a fiber to withstand when exposed to It is valuable for a fiber to withstand when exposed to organic solvents. Because these solvents has a high organic solvents. Because these solvents has a high tendency to contact with fabrics in day to day usage.tendency to contact with fabrics in day to day usage.Organic SolventsOrganic Solvents1. Ethyl alcohol1. Ethyl alcohol2. Methyl alcohol2. Methyl alcohol3. Paint thinner3. Paint thinner

Reaction to Organic Reaction to Organic SolventsSolvents

Bleaching is used everywhere in the textile Bleaching is used everywhere in the textile industry. industry. A fiber must be resistance to bleaching at least to a A fiber must be resistance to bleaching at least to a certain stage to become a good textile fiber.certain stage to become a good textile fiber.

Bleaching is done in fiber stage, Fabric stage and Bleaching is done in fiber stage, Fabric stage and garment stage as well.garment stage as well.

Effects of BleachingEffects of Bleaching

Resistance to MildewResistance to Mildew

Resistance to InsectsResistance to Insects

Insects stays in fabricsWhere they have enough Warmth, food and Protection as well.

Some fibers have good Insect repellent qualitiesFrom its nature Ex. linen

Since people are interested and interacted Since people are interested and interacted with colors, it is important for textile fibers with colors, it is important for textile fibers as wellas well

Ability to DyeAbility to Dye