textile science

8. YARNS

Yarn is a long continuous length of interlocked fibers, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery, or rope making.

Thread is a type of yarn intended for sewing by hand or machine. Modern manufactured sewing threads may be finished with wax or other lubricants to withstand the stresses involved in sewing. Embroidery threads are yarns specifically designed for hand or machine embroidery.

arns contribute significantly to fabric and product performance. Fabric producers must select from among a wide variety of yarns. Their selection may affect hand, appearance, drape, durability, comfort, and many other performance dimensions. For example, yarns with high twist create the texture in true crepe apparel and furnishing fabrics. Yarns with low twist are napped in flannel fabrics and blankets.

Yarn may enhance good fiber performance or partially compensate for poor fiber performance. The effectiveness of a finish may depend on the yarn choice. There are many different yarn types available. Factors that are used to identify and classify yarns include fiber length (staple/filament), yarn twist, yarn size, and yarn regularity/irregularity along its length. This chapter explains yarn identification, classification, and performance.

Yarn forms depending on;

a. The number of fibers twisted together.

b. The number of filaments laid together without twist.

c. The number of filaments laid together with more or less twist.

d. The single mono filament. e.g. Silk

TYPES OF YARNS:

Yarns can be made either from short staple length fibers or from filament fibers. There are two types of yarns, i.e., spun yarns and filamentous yarns.

Yarns can be classified based on length of fibers and number of parts present. Yarns are broadly classified as staple/spun yarns or continuous filaments. Spun yarns consist of short fibers assembled and bound together by twist to produce the required characteristics such as strength, handle and appearance.

Yarns

Spun yarns

Filament yarns

Smooth-filament

Yarn

Textured-bulk

Yarn

Napping

Average

Voile

Crepe

Low

(a) Staple and Filament

Characteristics of Spun Yarns and Filament Yarns

	Spun Yarn	Filament Yarn
1.	Yarns made from short length fibers	1. Yarns made from long length filament
	And the fabrics are like cotton and wool.	Fibers and fabrics are like silk.
2.	Short fibers twisted into continuous	2. Long continuous, smooth, closely
	strand, has protruding ends	Packed strand.
	1. Dull, fuzzy look	1. Smooth, lustrous
	2. Lint	2. Don not lint
	3. Subject to pilling	3. Do not pill readily
	4. Soil readily	4. Shed soil
	5. Warm (not slippery)	5. Cool, slick
	6. Loft and bulk depend on size and twist	6. Little loft or bulk
	7. Do not snag readily	7. Snagging depends on fabric construction
	8. Stretch depends on amount of twist.	8. Stretch depends on amount of twist
3.	Are absorbent	3. Absorbency depends on fiber content
4.	Size often expressed in yarn number	4. Size in denier
5.	Various amount of twist used	5. Usually very low or very high twist
6.	Most complex manufacturing process	6. Least complicated manufacturing process

TYPE OF YARNS

CLASSIFICATION OF YARN ACCORDING TO FIBER LENGTH

1. SPUN YARNS – spun yarn is composed of short-staple fibers that are twisted or otherwise bonded together, resulting in a fuzzy yarn with protruding fiber ends. Better-quality and more-expensive spun yarns are produced from longer-staple fibers

E.g.

i. Napping twist

· This type of yarn is also called the Low twist

· The low twist results in lofty yarns which are allowed for formation of napping fabric

· Napped fabrics are bulky and provides warmth when used in garments

ii. Average twist

· Its frequently used for yarns made of staple fibers and is very seldom used for filament yarns

· The amount of twist that gives warp yarns maximum strength is referred to as standard warp twist

iii. Hard twist(voile twist)

· This are yarns given 30-40 turns per inch to form a twist

· The hardness of the yarn results when twist brings fibers closer together and more compact

iv. Crepe yarns

· This may be single or two fold yarns which are highly twisted

· Crepe is a French word meaning crinkle

· The high twist causes the yarns to bend

· They make the yarn so lively and kinky

· The twist must be set before it can be woven or knitted

· Crepe yarns are used in fabrics like chiffons

Staple fiber yarns have a vast range of fiber yarns to be classified in a number of ways i.e. by construction (single, plied, cabled, multiple, fancy) and by spinning method, which is much more detailed method of classification.

Classification of spun yarns by spinning method

i. Ring spun yarns

These are produced on the ring and traveler system from a wide variety of fibers types. This is the most popular system of staple yarn production, as it utilises a wide range of fiber types, fiber finenesses and fiber lengths. The component fibers are twisted around each other to set up frictional forces between the fibers to impart strength to the yarn.

ii. Rotor spun yarns

Like ring spun yarns, they consist of fibers bound together by twist. Rotor spun yarns are generally only produced from short staple fibers. There are a number of differences in quality between ring and rotor yarns. In general rotor yarns are more regular but weaker than comparable ring spun yarns.

iii. Twistless yarn

These are yarns produced from staple fibers where the consolidation of the fiber is by means of some form of adhesive.

iv. Fascinated yarns

These are yarns consisting of a parallel bundle of fibers bound into a compact structure by surface wrappings at irregular intervals of staple fibers. Air-jet yarns are a typical example.

v. Warp spun yarns

These yarns consist of a parallel bundle of staple fibers bound into a compact structure by another yarn, usually continuous filaments. They can be produced using both long and short staple fibers.

vi. Core spun yarns

Core yarns are charcterised by having a central core wrapped with staple fibers. These are produced in a single operation by simultaneously feeding a yarn and staple fibers through the delivery rollers of a spinning frame.

A wide range of core yarn can be produced, e.g. cotton with filament core, hair fibers with cotton core and various fibers with an elastomeric core.

vii. Self-twist yarns

Self-twist yarns are two-ply yarns produced in a single operation. During manufacture, each component is twisted in alternating direction in short segments. The two components are subsequently put together in such a way that they twist together (self-twist) to form the final yarn. Self-twist are predominantly produced from long staple fibers.

viii. Friction spun yarns

These yarns are produced on spinning systems which use two rotating rollers to collect and twist individual fibers into a stable yarn structure.

2. FILAMENT YARNS

A filament yarn is composed of long fibers grouped together or slightly twisted together. Smooth-filament yarns have straight, almost parallel fibers. Uniformly bulky yarns are called textured-bulk-filament yarns or just textured-bulk yarns.

They are loosely twisted yarns made from natural silk or manmade filament fibers. They are fine and smooth, more pliable and more uniform in diameter than spun yarns. They are lustrous and shiny in appearance. Filaments can be separated when untwisted and can be counted. They produce high seam and yarn slippage. They are Stronger than spun yarns of the same diameter and fiber content.

i. Monofilament Yarn - It is a single strand of filament yarn and cannot be separated as it is an indivisible component.

ii. Multi Filament Yarns - Yarns are composed of two or more filament strands twisted together to form one yarn. When untwisted, each filament can be counted Combed worsted yarn

They are divided into two types:

1) Continuous filament

2) Textured continuous filament

1) Continuous filament/smooth

They are primarily man-made continuous filament yarn may be produced in either monofilament or multifilament form. They are smooth and silk-like as they come from spinneret

Their smooth nature gives them more luster than spun yarns. They resist pilling and fabrics made from them tend to shed soil easily

Standard-filament yarns are known as ‘flat’ filament yarns, in contrast to textured yarns.

2) Textured continuous yarns

· They are man-made continuous filament yarns that have been modified by subsequent processing to introduce durable crimps, coils or other distortions into the filament or with high twist or low twist

· The addition of twist increases bulk texturing giving slippery filaments the aesthetic property of spun yarns by altering the surface characteristics and creating space between the fibers

· The thermal and moisture absorption is also improved

YARN CLASSIFICATION ACCORDING TO THE NUMBER OF PARTS IN YARNS

v COMPOUND YARNS

These are quite simple yarns with more than one strand. Sometimes they are referred to as complex or multiple yarns

v Single yarn, Ply Yarn and Cabled yarns

a) Single yarn

A number of fibers are twisted together into a continuous length, the yarns consists of one kind of fiber

· This type of yarn is the one usually found in most standard fabrics for clothing and household use and purposes

Twist ply yarn

b) Ply yarn

Two or more than two single yarns are twisted together to form a ply yarn. The yarns are known as multiple strand yarn. If two single yarns are twisted together the resulting yarn is known as two ply yarn

c) Cord /cable

It’s made by a third twisted operation in which ply yarns are twisted together. Folded and cabled yarns can be produced from staple yarns, continuous filament yarns or a combination of both.

Some type of sewing threads and some ropes belong to this group. Cords are seldom used in apparel fabric but also used in industrial weight fabrics

d) Double yarn

A yarn in which two or more single yarns are twisted together in a single operation e.g. two-fold, three-fold, four-fold.

These are used for ornamental effect as the low twist yarns produce luster and softness

Single, Ply and Cord Yarns

Cord Yarn

Single Yarn

Ply Yarn

Cord yarns are

A single yarn is made

A ply yarn is made by

Directly from fibers.

Second twisting operation

Composed of two or more

Which combines two or more

Ply yarns combined for

Singles. Each part of the yarn

Is simple cord yarns, the

Called a ply. The twist is

Singles used to make the

Inserted by a machine called

Ply yarns and the ply yarns

“Twister. The ply yarn is also

Used to make the cord are

Known as folded yarn.

Simple yarns.

v Novelty yarns/Fancy yarns

- Fancy Yarns Fancy yarns are yarns that deliberately have unlike parts and that are irregular at regular intervals. The regular intervals may be subtle or very obvious.

- Fancy yarns may be single, plied, or cord yarns. They may be spun, filament, or textured yarns—or any combination of yarn types. They are called fancy yarns or novelty yarns because they produce an interesting or novel effect in fabrics made from them.

- Their structure may be complex and consist of several yarn plies combined into one yarn. Fancy yarns are classified according to their number of parts and named for the effect that dominates the fabric. Usually more common in furnishing fabrics than in apparel fabrics, fancy yarns also are used by artists and crafts people to create interest in otherwise plain fabrics of many fiber types.

Characteristics;

· It’s characterized by irregular twists and loops

· They are usually ply yarns of different kinds of fibers or of different colors

· They are also constructed from simple yarn by varying the amount of twist

· For its construction at least one or two single yarns are used

· Fancy yarns add permanent interest to plain fabrics at a lower cost.

· Fancy bulky yarns add crease resistance to a fabric, but they may make the fabric hard to handle.

· The durability of fancy yarn fabrics depends on the size of the ply effect, how well it is held in the yarn, the fiber content of the various parts, and the firmness of the fabric structure.

· These types of yarns are mostly used for drapery, upholstery fabrics

Fancy yarns

Single yarns

Ply yarns

Tweed

Slub

Ratiné

Spiral

Knot

Snarl

Bouclé

Slub

Yarns.

Types of novelty

1) Slub yarn

· This is a yarn made with thick and thin placing by varying the amount of twist in the yarn at regular intervals

· They are found in drapery and upholstery fabrics

The slub effect is spun into the yarn.

Slub yarn

2) Spiral or corkscrew

Have two or more plies. The plies may differ in color, twist, size, or type. A two-ply fancy yarn may have one spun ply combined with a filament ply. The two parts may be delivered to the twister at different rates of speed. These yarns are used in furnishings and apparel.

Spiral/corkscrew

3) Thick and thin yarns

· They are made from filament like slub prepared from staple’s

· The pressure forcing the spinning solution is varied in the filament where produces thick yarns in some places and thin yarns in some

4) Boucle yarns

· They are characterized by a projecting from the body of the yarn at fairly regular intervals

· They are three ply yarns

· The effect yarns forms irregular way surface and binder ties it to the base

5) Loop ,curl and Gimp yarn

· It’s the same as boucle but the effect yarn is regular, semicircular appearance while in loops

Loop yarn

6) Snarl or spike yarn

· It’s made by twisting together two ply yarns that differ in size, type or twist

· These two parts may be delivered to the twister at different rates of speed

· This is made in the same way as a loop yarn, but using a highly twisted effect yarn which forms snarls rather than loops.

Snarl

7) Chenille yarn

· It means caterpillar in French

· The yarn has a cut pile effect which is bound to the core on the loom warps

· They are arranged in groups (2-6) which are interlaced in a cross weaving manner

· Weft is inserted in a normal manner and these are cut into wrap way threads

8) Metallic yarns

· These are primarily decorative

· The plastic coating on it resists tarnishing but care must be taken while pressing as pure metals are soft

a. Bouclé

b. Eyelash

c. Flammé

d. Ladder

e. Ribbon

f. Slub yarns

9) Fleck

Small amounts of fibers of either different colors or luster or both, are introduced into the yarn. This gives it a spotted and short streaky appearance.

Fleck yarn

10) Cloud

A two-color yarn, in which both yarns take it in turn to obscure or cloud the other, giving the appearance of an intermittent color change

11) Knop (button)

This features prominent bunches of one or more of the component yarns at regular or irregular intervals

12) Eccentric

This is basically an undulating gimp yarn, produced by binding an irregular yarn in the opposite direction to the initial twist, creating graduated semi-circular loops.

CLASSIFICATION ACCORDING TO THE TWIST DIRECTION

YARN TWISTING

· Twist is the spiral arrangement of the fibers around the axis of the yarn, Twist binds the fibers together and gives the spun yarn strength and It is away to vary the appearance of fabrics

· The amount of twist inserted in a yarn defines the appearance and the strength of the yarn

· The amount of twists is referred to as TURNS PER INCH(TPI) or TURNS PER METRE

Twist direction

Twist can be inserted in either of two directions, clockwise or anticlockwise. The usual designation for twist direction is to use the letters S or Z.

A single yarns has S twist if when it is held in a vertical position, the fiber inclination to the axis of the yarn forms the centre of the letters S.

Similarly, the yarn has Z twist if the fiber direction forms the centre of the letter Z.

The majority of single yarns are spun with twist in the Z direction, S twisted yarns are often called revers twisted by the spinner. The twist characteristics, that is the way the yarn behaves, is totally unaffected by the direction of twist in single yarns.

Twist factor

The angle of twist is the factor that determines how the yarn will behave.

· Yarns with low twist level will have a lower angle of twist, and will be relatively soft, bulky yarns.

· Yarns with higher twist angle will be strong, lean and hard yarns while

· Over-twisted yarns will have very high twist angle, they will be very hard, weaker and twist lively, that is they will snarl easily under tension.

Factors that determine result in yarn twist

· Quality of fabric used

· Count of yarn to be spun

· Fineness of the fiber being spun

· The softness of the fabric into which is the yarn is to be converted

· The length of fibers

· The dimensions of the yarn

· The meant use

Physical properties and performance characteristics of different yarns:

Yarn type	General yarn properties
Staple yarns : Carded cotton, Combed cotton, Woolen , Worsted, Linen	Excellent handle, good covering power, good comfort rating; reasonable strength; reasonable uniformity
Continuous filament yarns : Natural, Non-synthetic, Synthetic	Excellent uniformity; excellent strength; can be very fine; fair handle; poor covering power
High bulk yarns : Staple, Continuous filament	Good covering power with light weight; good loftiness of fullness
Stretch yarns : Continuous filament	High stretch ability; good handle and covering power
Special end-use : Tire cord, Rubber/elastic Core yarn, Cabled, Coated	Purely functional; designed to satisfy a specific set of conditions.
Novelty yarns : Fancy yarns, Metallic,	Excellent decorative features or characteristics

Yarn count/yarn numbering system

Different yarn numbering systems are used for cotton, linen, wool, and silk or synthetic yarns. Traditionally yarns have been bought and sold by weight rather than length. To further complicate matters, each yarn manufacturing system (cotton system, wool system, etc.) had its own unique measuring / numbering system to describe the weight (hence size) of the yarn produced. The various systems can be categorized as either direct yarn numbering systems, or indirect systems.

Is the measurement of yarns sizes and thickness or can be defined as yarn coarseness and fineness

· There are two systems of yarn counting based on either fixed weight or fixed length

· These systems are:

1) Direct system of yarn count

2) Indirect system of yarn count

Yds

840

bs=1S

Numbering system

Matric No.

English No.

Direct

Indirect

Denier

Tex

900

Gms=1 Denier

Tex = 1gm/km

/1=50 single yarns

1) Direct system of yarn count

It’s based on weight of a yarn per unit length

Direct yarn numbering systems quantify the weight per a standard length of yarn. As the weight of the yarn increases, so does the numerical value assigned. Silk and most synthetic yarns are measured using the direct system. One unit of measure is called denier. The weight of a yarn using this system is expressed as the number of grams (weight) per 9000 meters (length). The higher the denier of a yarn, the greater its weight (per given length of yarn), therefore the higher the denier, the heavier and often thicker the yarn.

· We have various systems of yarn counting. This are:

i. Text

The tex system is defined as the weight in grams of one thousand metres of the material

· The smaller the text the finer the yarn

ii. Denier system

Denier is a direct system, defined as the weight in grams of nine thousand metres (9000m) of the material

It is usually used for monofilament and multifilament yarn

· Its weight in grams of 9000 meters of yarns

2) Indirect system of yarn count

This is based on length per unit weight

With indirect yarn numbering systems, the weight / length relationship is reversed. The larger the number assigned to a given yarn, the lighter (and generally thinner or finer) the yarn. While there are several different indirect systems, each based on one or another of the different yarn manufacturing systems (e.g. cotton, wool,…) the most commonly used today is the measurement system from the cotton system. Because cotton, wool, and linen yarns typically are plied (two or more individual yarns are twisted together to form a stronger, thicker yarn), the yarn numbering system derived from these manufacturing systems indicates the number of ply.

· In this system there are different yarn counts. This are:

i) Cotton count

· It is the number of hanks each 840 yards in length which weigh one pound each

· Mostly used for cotton spun yarns

· Hank is a yarn package

ii) Metric Count

· This is the number of km (100m) of yarn weighing one kilogram

· The smaller the metric count the thicker the yarn

iii)Woolen count

· This is the number of hanks each measuring 256 yards in length which will weigh one pound

· Used to measure wool

· The smaller the count the thicker the yarn

iv)Worsted count

· Is the number of count each measuring 560 yards in length which weigh one pound

· Mainly used on worsted spun yarns

· The greater the count the finer the yarns or the smaller the counts the thicker the yarns

YARN FORMATION PROCESSES

The twisting process by which fibers are formed into a yarn is referred to as spinning. Spinning includes all the processes required to prepare and clean the fibers from the opening of the bale to the twisting of the yarn in its preparation for the textile loom.

1. Cleaning

All natural fibers must be cleaned and separated before processing. Seeds (e.g. cotton) must be removed, dirt and other foreign matter must be removed (plant and animal fibers). Processing fibers without properly or thoroughly cleaning them causes very poor quality yarn not suitable for apparel. Bales of raw fiber are opened and fed into machines that separate dirt and debris from fiber.

2. Opening and Picking/ Cleaning

In order to produce a uniform product, the fibers from numerous bales be blended, or thoroughly mixed together, and from this composite, the final yarns will be produced. The masses of fibers from these numerous bales will be fed into a machine called a blending feeder. As these masses of fiber are loosened and thoroughly mixed, some remaining heavy impurities such as dirt, remnants of seeds, leaves or stems, are removed by a line of machine known respectively as pickers, breakers, intermediates and finishers each in succession being a somewhat more refined cleaner of the raw fibers. From these machines, the fabric emerges as a lap, a loose, formless roll.

3. Carding :

The lap is unrolled and drawn onto a revolving cylinder covered with fine hooks or wide bristles. These wide bristles pull the fibers in one direction, separate those which are individually tangled together and form them into a thin film. This process is known as carding. The thin film is drawn into a funnel shaped opening which molds it into a round rope like strand approximately an inch in diameter; this is called the sliver.

4. Combing : Untangling, Straightening and laying fibers parallel to achieve order

The comber is a refining device by which the paralleling and straightening of the individual fibers is carried to a more exact degree. The longer fibers are again formed into a sliver, known as the comb sliver.

5. Drawing :

In the drawing operation, further blending is accomplished by working together several slivers and drawing or pulling them out in the drawing frame without twisting but reducing the several slivers to a single one about the same diameter as each of the components. (Drawing out of straightened fibers to achieve the thickness of the yarn required)

6. Roving :

The combined or condensed combed sliver is taken to the slubber of a series of machines called roving frames. In order to give yarn strength, the sliver must be further elongated and some twist must be imparted to hold the individual fibers together more tightly. The sliver is pulled (drawn) and twisted down to a roving, the size of an ordinary pencil.

Left: slivers feeding into roving frame

7. Spinning :

Spinning is a continuation of the roving and on the spinning frame many spools containing the roving pass through the ring spinning mechanism which further draws and twists to a yarn of the required size and twist and winds it on bobbins preparatory to the weaving operation. Different methods may be used for spinning, but ring – spinning and open – end spinning are the most common. After spinning, yarn is wound onto a thick cardboard or plastic cone, or onto a bobbin, depending upon how it will be used.

Left: Ring spinning frame producing cotton yarn

Right: Cone of yarn

Spinning methods

The insertion of twist into a strand of fibers is the conventional method used to generate forces necessary to prevent the fibers slipping past one another. It is this resistance to fiber slippage which gives rovings, slubbings and yarns their actual strength

Types of spinning include:

1) CAP of spinning

2) Flyer spinning

3) Mule spinning

4) Ring spinning

1) CAP of spinning

· In this type of spinning the cap like a dome is stationary

· A bobbin is slipped in the cap and the bobbin is slipped over a spindle

· The cap is pressed onto the tip of the spindle

· As the bobbin is revolved it drags the roving around the edge of the cap

· In relation to the speed of rotation the roving emerging from the first pair of drafting roller is pulled and twist is inserted

· It produces hairy yarn because of the friction created as the yarn laps around the edge of the cap

2) Flyer spinning

· A spindle is fitted in the bobbin loosely

· The flyer is pressed on the tip of the spindle which causes which causes it to rotate rapidly pulling the bobbin around with it as they collect the yarn being span

· In relation to the speed of rotation the roving emerging from the 1^st pair of drafting roller is twisted

· Flyer spinning is used to reduce rovings’ in worsted and woolen yarn manufacture.

3) Mule spinning

· The roving emerges from slow pair of drafting rollers

· Drafting of the roving occurs as the rotating bobbin and the spindle travel more away from the rollers

· Drafting and twisting are completed at the end of the travel then a fuller wire pushes the strands of the yarns downward so that the spindle carriage moves back towards the drafting rollers

· The yarns are then wound on the bobbin

4) Ring spinning

· It’s a very high method of yarn manufacture

· Is the most common method of twist insertion and it’s the most dominant method of doubling plying yarn

· It produces a hairy yarn but very commonly used because of the high rate of production and relatively low cost of manufacture

· It has 2 economic advantages

i. Produces too small yarn package

ii. Its labor intensive

· About 98% of yarn manufacture is produced by ring spinning

· The rotating bobbin with the aid of the traveler inserts twist on the yarn

· As the traveler slightly lags behind the bobbin the yarn is wound on the bobbin

5) Open spinning

· This is an economical method of manufacturing mainly cotton and other short fibers yarns

· It produces medium to thick yarns

· As the name suggest an open end is created in the flow of fibers

· The yarn being produced has one end free

Single fibers are separated and then rotated and joined to the open end of the twisted yarns which also rotates

Principles of open end spinning

· Fibers in sliver form are fed to an opening device which is usually a single spiked roller

· This opens the sliver completely so that fibers can be fed forward individually. This is where the break occurs in the spinning system

· The fibers are transported from the opening unit by an air stream

· They are collected in the inner surface of a cup-shaped rotor

· The rotor revolves at a high speed

· During each revolution a thin layer of fiber is deposited in its inner circumference

· This inner circumference is called collecting groove

· The fibers are held in the collecting groove by centrifugal force as a multi-layered strand

· The strand is pulled from the collecting groove s it is withdrawn to form the yarn

· Twist is inserted by the rotation of the rotor

· The completed yarn is withdrawn through the yarn tube by the yarn take off rollers

Advantages of open end spinning

· It requires limited labor

· Cost of power is reduced

· There is utilization of short waste fibers (requires recycling)

· Bigger packages

· Saves time

· Have good quality yarns without knots

Disadvantages of open end spinning

· A hard twisting is produced. (It has a dry handle)

· It is not versatile. (Cannot have many uses)

· Weak yarns are produced (Some yarns may not be strong)

· Dirty yarns hence they were not cleaned during combing process

· The operator needs to be highly skilled

Suitable fibers for spinning must have the following features

· Adequate strength

· Pliability

· Cohesiveness

· Strength

TEXTURING

One way of processing man-made filaments to produce a yarn similar in properties to one made from natural fibers is to cut up filaments in short lengths (staple fibers) and spin them on convectional staple spinning machines. This method is widely used to produce 100% staple yarns and also man-made/natural fiber blends.

This process of cutting up continuous filament yarn only to reassemble it in another yarn form seemed illogical. And therefore in the 1950s new methods were developed to add crimp and deformation (texture) to continuous filament yarns in order to confer on them some properties similar to those of yarns made from natural fibers. This process is known as texturing

Texturing methods

1. False twist texturing

Consists of inserting a very high twist into a continuous filament yarn, setting this twist by a heat treatment and then completely untwisting the yarn. Because of the stable state of the yarn in its full twisted heat-set condition, the untwisted yarn behaves like an assembly of springs. When the tension is reduced, each filament tend to bulk up into a mass of tangled filaments.

2. Post-texturing process

Many items of clothing, especially outer wear, require bulk and warmth provided by the false twisted yarns but not the excessive stretch. Before use in woven or knitted structures, the textured yarn can be stabilised usually by a second heat treatment, which has the effect of reducing stretch and giving increased bulk.

3. Stuffer-box texturing

It is based on the principle of heat setting filaments which are held in a confined space in a compressed state (deformation) and then withdrawing them in a crimped form. This method gives yarn a high bulk, soft handle and less stretch than false twist yarns

This method is widely used to crimp man-made staple fibers

4. Air-jet texturing

Filament yarns are fed over tiny blast of air that forces the filament into loops. This type of yarn is called air-textured or air-entangled

5. Knit De knit

A flat yarn is knitted, the knitted fabric is heat set and the fabric is then unravelled. The crimp frequency and shape can be varied by changing the needle gauge and fabric structure.

Fabric produced in this method has pronounced sparkle, bouncle-type texture, good stretch and recovery and good handle

6. Gear crimping texturing

Filament yarns are passed through closely meshed gears, Intermeshing gears introduce a two-dimensional crimp to filaments. Heat can be used to permanently set the crimped filaments.

Advantages of texturing

a. Higher bulk

b. Increased warmth

c. Greater water absorption

d. Good draping capacity

e. Higher covering power

f. Better dimension stability

g. Higher air permeability

Disadvantages

a. Increased hairiness

b. Reduced strength and abrasion resistance