Fibrous Material And Yarns

Nature of fibres and origin Natural fibres- Plant origin Animal origin Mineral origin Man made fibres-Regenerated Fully synthetic

Natural fibres Fiber, also spelled fibre, is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread. Vegetable fibres are generally based on arrangements of cellulose, often with lignin: examples include cotton, hemp, jute, flax, ramie, and sisal. Plant fibers are employed in the manufacture of paper and textile (cloth), and dietary fiber is an important component of human nutrition. Animal fibers consist largely of particular proteins. Instances are spider silk, sinew, catgut, wool and hair such as cashmere, mohair and angora, fur such as sheepskin, rabbit, mink, fox, beaver, etc. Mineral fibers comprise asbestos. Asbestos is the only naturally occurring long mineral fiber. Short, fiber-like minerals include wollastonite, attapulgite and halloysite. Man made fibres Synthetic or man-made fibers generally come from synthetic materials such as petrochemicals. But some types of synthetic fibers are manufactured from natural cellulose, including rayon, modal, and the more recently developed Lyocell. Cellulose-based fibers are of two types, regenerated or pure cellulose such as from the cupro-ammonium process and modified or derivitized cellulose such as the cellulose acetates. Fiber classification in reinforced plastics falls into two classes: (i) short fibers, also known as discontinuous fibers, with a general aspect ratio (defined as the ratio of fiber length to diameter) between 20 to 60, and (ii) long fibers, also known as continuous fibers, the general aspect ratio is between 200 to 500[1]. Regenerated fibres are those fibres which are regenerated from nature example viscose, modal, lyocell. Fully syntetic fibres are those fibres which are fully manufatured from chemical products example nylon, polyester, acrylic, aramid, polyethylene

Fibre structure Amorphous region  disorderly arranged 

Crystaline region  Orderly arranged 

Differences between crystaline and amorphous regions -

The crystaline region is densely pack whereas in the amorphous region the chains are loosely pack. The interchain forces are stronger in the crystaline region than in amorphous region, the forces of attraction are inversely proportion to the square of distance. Accessibility to water and chemical are much higher in the amorphous region.

Properties of fibres 1. Density Mass Volume

=

mass area x length

The denser a material is, the less of it is needed to weight a certain mass.

2. Tensile Strength It is the ability to resist tensionÆacts on the longitude of the textile fibres Tensile strength is the maximum load that a material can withstand without breaking. -unit that is use to measure tensile strength is centi Newton. To compare the strength of two fibres, you must compare light to light not light to thick. It has to bring down to the same finess. 3. Tenacity Tenacity is the breaking load, that is the maximum or minimum load that cause a fibre to break.

Tenacity = tensile strength Tex Only by comparison of tenacity that we can conclude that a fibre is stronger than an other fibre. 4. Extensibility/Elongation - When subjected to a load, by what amount the fibre can be extended without breaking. - The elongation at which the material breaks is known as the elongation at break.

Lo Lf

Extension = Lf - Lo Elongation = extension initial length

Elongation at break

= е Lo

E.g Lycra has got good elongation whereas glass has got very low elongation. 5. Elasticity - A recovery from extension Note: the more elastic a material is the most it will recover. Rubber is the most elastic material.

Lo

L1

e e1 e1 is the elastic recovery of the material 6. Malleability It is the ability of a material to withstand deformation by compression before cracking. 7. Ductility - It is the ability of a material to be deformed under tension before it damages. - The ductility of material decreases as the temperature increases, making them weaker at high temperature. 8. Toughtness It is the ability of a material to withstand sudden impact without fraction and also the ability to withstand bending.

9. Plasticity It is the ability of a material to be permanently changed in shape or form by external forces or casting. 10. Hardness It is the ability of a material to resist abrasive wear, indentation or deformation. 11. Durability It is the ability of a material to withstand wear and tear weathering and corrosion. 12. Stability - It is the ability of a material to resist changes in size and shape due to environment. - It is also known as dimensional stability. 13. Strength It is the ability of a material to resist force without breaking. Different force requires different types of strength to resist them. - Tensile strength It is the ability of a material to resist stretching or pulling forces.

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Compressive strength It is the ability of a material to resist pushing forces.

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Bending strength It is the ability of a material to withstand bending forces

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Shear strength It is the ability of a material to resist sliding forces acting against each other.

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Tortional strength It is the ability of a material to withstand twisting force under tortion or tork.

Physical properties Physical properties refer to the matter that forms the material. -

Fusibility It is the ability of a material to change into molten or liquid state when heated to a certain temperature.

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Density It is defined as mass per unit volume..d=m/v It is essential for calculating mass and volume.

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Electrical insulator They are materials that are resistant to the flow of electricity. They are known as insulators.

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Thermal expansion It relates to the expansion and contraction of a material due to heating and cooling.

Optical properties It refers to how a material reacts to light, heat, reflection, radiation and absorption. A material can be translucent, transparent and opaque. Opaque- does not allow light to pass through it and vision also. Transparent- it allows light and vision to pass through it. Translucent- it allows only light to pass through.

Identification of fibres - Morphology: - the study of forms. - Form of cross section - Longitudinal shape…how does the structure look like? - Solubility in acids, bases and solvents. - Burning tests- ignition, form after burning, flame color and smell.

Technical Tests for Fiber Identification There are two types of methods that are used for identifying different fibers - the nontechnical tests and the technical tests. The nontechnical tests include the feeling test and the burn test. The technical tests include microscope test and chemical test. The technical tests for fiber identification are carried out in laboratories and require technical knowledge and skills. As such, they are much more reliable methods for testing end product as compared to the non technical tests. The Nontechnical Tests- Feeling Test and Burning Test Feeling test involves touching a fabric and feeling the fabric to know its component fibers. For example, wool fabrics will feel warm when touched because the heat generated by wool, which is a nonconductor of heat, will remain in the touched area itself. On the other hand, the fabrics made up of plant fibers such as cotton fabrics, linen fabrics and even the rayon fabrics, that are made from the cellulose of wood pulp or cotton fiber, feel cool to touch. As they are conductors of heat, the heat generated by the finger passes off making the fabric cold. However, it requires a long experience of handling different fabrics over a period of time for such skillful perception. Also, it is difficult to examine and compare the fabrics made of different fiber contents with the feeling test. The other nontechnical test for fiber identification by the burn test- involves burning a sample of fabric and observing the various characteristics shown by it after burning in order to determine its fiber content. The burning test is more efficient than the feeling test but it also has its limitations. For example, fabrics made of biconstituent fibers, that are combination of two different textile polymers, can not be identified with this test. NATURAL FIBERS (ANIMAL) Fiber Wool

Silk

Smell

Ember and Flame

Burning Hair

Small flickering flame, brittle ash, no smoldering (will not burn after flame is removed).

Burning Feathers

Calm flame, no smoldering. (Will not burn after flame is removed). Black beads, crushable.

NATURAL FIBERS (VEGETABLES) Fiber

Smell

Rayon (Synthetic)

Burning Wood

Ember and Flame Rapid burning flame, slow burning embers, no ash, no

bead. Cotton

Burning Paper

Flame amber or yellow, slow burning; fluffy grayish ash.

SYNTHETIC FIBERS (MAN-MADE) Fiber

Smell

Nylon

Boiling green vegetables (string beans or celery)

Olefin

Asphalt

Acrilan (Acrylic) Polyester

Ember and Flame Dissolves and forms an effervescent flame; produces a hard, amber-beaded ash. Melts and produces a scorching flame; forms a hard tan bead.

Sharp, pungent, unpleasant Hard, black residue. Burns odor quickly. Sweetish

Burns rapidly; produces a black, hard, rounded ash.

The Technical Tests- Microscope Test and Chemical Test The technical tests for fiber identification done with the help of laboratory equipment are far more reliable than the nontechnical tests. However, technical knowledge and skill, particularly while handling chemicals, are the basic requirements for conducting these tests. Microscope Test Microscopes having magnification of at least 100 power, can be successfully employed for testing and identifying the fiber contents of a fabric. Microscope test is very effective for testing the natural fabrics. Difficulties can be faced while testing synthetic fabrics as many of them have similar appearance. However, one must know, what the fibers look like under a microscope as many finishing processes like mercerizing and delustering, change the appearance of fibers under microscope. Apart from it, dark colored fabrics also cannot be tested with microscope as light cannot pass through dark substances. For such fabrics, either the textile dyes haveto be removed by stripping, bleaching etc. or they have to be chemically tested. Natural fibers have their own peculiar structures, spots, lines and other marks that help in identifying them. Following are some examples of natural fibers and how they look like under a microscope: Cotton: The cotton fiber is a single elongated cell. Under a microscope, it looks like flat, spirally twisted ribbonlike tube with rough granular surface. However, mercerized cotton doesn't have natural twist. The finishing process makes them swollen, straight, smooth and round with a shining surface. Linen: Linen fiber, under a microscope, looks like having multiple sided cylindrical filaments with fine

pointed edges. The filaments show nodes at intervals. It, in fact, looks like a bamboo stick having

joints that results into a little unevenness. Wool: Wool fiber has irregular, roughly cylindrical, multi cellular structure with tapered ends. Under a

microscope, three basic layers are shown- epidermis (outer layer), cortex (middle layer) and medulla (inner layer). Medulla is seen only in coarse and medium wool fibers and that too under a highly powerful microscope. Silk: Raw silk fiber, composed of two filaments, has elliptical shape under the microscope. The two fine

and lustrous filaments are shown clearly looking like transparent rods with triangular shape. Wild silk or tussah fiber has different appearance than the cultivated silk. It is flattened, coarse, thick and broader fiber having fine, wavy lines all across its surface whereas cultivated silk is narrower fiber with no marks on it. Manmade fibers are difficult to identify through microscope because of similar appearance of many fibers. However, their certain distinguishable characteristics under a microscope have been mentioned below. Rayons: Rayon fiber has uniform diameter with glass like shine. If delustered then

rayon fiber shows marks similar to pepper, when viewed cross sectionally. Viscose fiber of rayon looks irregular when viewed cross sectionally.

Acetate: Acetate fiber looks lesser irregular than viscose rayon when viewed cross

sectionally. It has indentations that look like occasional marks when viewed longitudinally. Nylon: There are many variants of nylon fiber. However, generally it appears fine, round, smooth and

translucent. Sometimes it has shiny appearance. If it looks dull, it will also be dotted under the microscope. Aramid: If viewed longitudinally, aramid fiber looks smooth and straight. If viewed cross sectionally, it

may be round or like peanut's shape. Polyester: Generally, polyester fiber is smooth, straight. It looks round cross sectionally. However, with

various finishing processes, its appearance changes in context of texture and luster. Spandex: Spandex fiber have the outstanding characteristic of appearing like groups of fibers fused

together. However, different variants of spandex show different characteristics too. The Lycra fiber looks like fused multifilaments cross sectionally. Individual fibers are dotted and in shape like that of dog-bone. If viewed longitudinally, they appear straight. Polypropylene: When viewed cross sectionally, polypropylene fiber looks somewhat round but it looks

straight and smooth when viewed longitudinally. Glass: The glass fiber looks smooth, round, translucent, shiny and flexible.

Chemical Tests Chemical tests for fiber identification can only be conducted in well equipped laboratories. There are two primary methods to conduct chemical testing- stain and solvent.

Stain Meth hod: Stain tec chnique uses acid a and alka ali on differen nt fabrics to identify i theirr

fiber conttents. Most off the fibers have two colo or reactions when w treated with stain. A fiber stain ned with dilute acetic acid d turns to a specific s color. The same fiiber when stained with w mild alkali like soda ca arbonate turn ns to a different color aga ain specific to that fib ber only. Ace etate changess to light gree en color when n acetic acid is used and turns oran nge when dilu ute carbonate e of soda is used. Likewise e, nylon turnss beige in one and bright b red in other. o As dou uble testing iss done in this method, it iss sometimes referred to t as double-barreled stain identification. Solvent Me ethod: Various solvents are e used in thiss method to distinguish d one kind of fibe er from anoth her.

However, there is no single s solventt or chemical that can be used on all fibers. Additio onally, differe ent solvent prrocedures are e adopted to separate and d identify the e fibers that are a combined together. It becomes very v difficultt to use solvent methods in n view of fibe ers that have similar chem mical characterristics. Also, when w more fibers are mixe ed to produce e blended fab bric, then also it becomess tough to identify i the fibers f with the help of solvvent method.. However, itt is a very effe ective metho od for cross checcking but in order o to have e accurate rep ports, the fab bric has to be e cleaned thoroughly and the t finishing chemicals c sho ould also be removed r com mpletely. The fabric has to o be unraveled d, yarns have e to be untwissted and the fibers f have to o be put in th he solutions in n as loose a condition c as is possible e. As an example of solve ent method, consider c diffe erentiating an nimal fibers from f plant fibers witth alkali. If wool or silk fib ber has to be eliminated frrom a blende ed fabric then stron ng alkalies ca an be used be ecause animal particles are e destroyed in i it. Five percent of o caustic soda or sodium hydroxide h is used u in waterr. The action of the chemical is hastened by b boiling the e solution beffore immersin ng the sample e fabric in it. The wool or silk fiber gets g completely dissolved in it. The pla ant fibers rem main unaffectted. For differentiating them, acid a has to be e used as the e dilute acids destroy plant fibers. A drrop of sulfuricc acid has to be put on the sa ample fabric which, in turrn, is placed between b two o blotters and d pressed with h hot iron. If it contains cottton, linen or rayon then th he fabric getss charred at the t spot.

Basic spiinning proccess

Principlees of ring an nd open-end d spinning Ring spinning is a method m of spinning fibress, such as cootton, flax orr wool, to maake a yarn. The T ring fram me developed d from the thhrostle framee, which in itts turn was a descendantt of Arkwrigght's water fraame. Ring sp pinning is a continuous c p process, unlikke mule spinnning which uses an intermitteent action. In n ring spinniing, the roving is first atttenuated by using drawiing rollers, thhen spun andd wound arou und a rotatinng spindle whhich in its tuurn is containned within ann independeently rotating ring r flyer. Trraditionally ring frames could only be b used for the t coarser countsc but thhey could be attended by y semi-skilledd labour.

Open end spinning is a technology for creating yarn without using a spindle. It was invented and developed in Czechoslovakia in Výzkumný ústav bavlnářský / Cotton Researching Institute in Ústí nad Orlicí in the year 1963. It is also known as break spinning or rotor spinning. The principal behind open end spinning is similar to that of a clothes dryer spinning full of sheets. If you could open the door and pull out a sheet, it would spin together as you pulled it out. Sliver from the card goes into the rotor, is spun around into yarn and comes out, wrapped up on a package, all ready to go to the next step. There is no roving stage or re-packaging on an autoconer. This system is much faster than ring spinning with rotor speeds up to 140,000rpm , and less labour intensive. Several design of rotors are used by different manufacturers; designed for different fibres. The first open end machines in the UK, were placed under great secrecy, in Maple Mill, Oldham in 1967. The disadvantage is mainly that the open end is limited to coarse counts, cloth made from openend yarn having a 'fuzzier' feel and poorer wear resistance. System of spinning based on putting twist into the yarn without turning the bobbin. This is done by rotating the yarn end at a gap or break in the flow of fibers between the delivery system and the yarn take-up (bobbin). Open end spinning is usually not as smooth and soft as ring spinning. The production of spun yarns by a process in which the sliver (q.v.) or roving (q.v.) is opened or separated into its individual fibres or tufts and is subsequently reassembled in the spinning element into a yarn. A Spinning System In Which Sliver Feedstock Is Highly Drafted, Ideally To Individual Fibre State, And Thus Creates An Open End Or Break In The Fibre Flow. The Fibres Are Subsequently Assembled On The End Of A Rotating Yarn And Twisted In. Various Techniques Are Available For Collecting And Twisting The Fibres Into A Yarn, The Most Noteworthy Being Rotor Spinning And Friction Spinning.