5 Yarn – introduction, classification – simple, ply and speciality yarns yarn number, blending

P. Sivakumar

YARN INTRODUCTION:

Yarn is a long continuous length of interlocked fibres preferably using twist, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery, and rope making.

A textile yarn is an assembly of substantial length and relatively small cross section of fibers and/or filaments with or without twist”.

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.

The most common plant fiber is cotton, which is typically spun into fine yarn for mechanical weaving or knitting into cloth.

SSpun Yarn Or Staple Yarn

Spun-staple yarns consist of staple fibers assembled and bound together by various means (usually twist) to produce the required characteristics such as strength, handle and appearance.

Short Staple Yarn: Yarn produced using less than 60mm fibres are called short staple yarn.

i) Ring Spun Yarn:

These are produced on the ring and traveller twistsystem from a wide variety of fibre types

length ranges from 15 mm to 50mm.

The softness changes with respect to twist. Used to produce woven fabrics, knitted fabrics, home textile materials and industrial fabrics.

It is of mono-structure, has hairy fibres on its surface. Highly cohesive in structure.

Yarn properties: high tensile strength
Moderate uniformity,less production rates
Application: yarns for warp woven, knitting and weft yarns
DisAdvantages: high manufacturing cost;
High energy expenses and labor cost

Three phase structure. Core, sheath and belt/ wrap fibres. Typical characteristics of this so-called core-twist are therefore a harder handle accompanied by a lower strength than is obtained with sheath-twist, since the outer layers have relatively little twist and can thus contribute little to strength. However, abrasion-resistance is often better. Removal of outer fibers due to abrasion has little effect, since these fibers did not create much strength anyhow. In rotor-spun yarns, this outer layer exhibits other peculiarities. One of these is the presence of wrap fibers. These are fibers which fly directly onto the fully created yarn as the rotor passes under the feed passage.

iii)Friction Spun or Dref yarn

These yarns are produced on spinning systems which use two rotating rollers tocollect and twist individual fibers into a Stable yarn structure.Friction Spinning or Dref Spinning is a textile technology that suitable for spinning coarse counts of yarns and technical core-wrapped yarns.

Dref yarns are bulky, with low tensile strength making them suitable for blankets and mopyarns, they can be spun from asbestos, carbon fibres and make filters was water systems.Yarns such as Rayon and Kevlar can be spun using this method

Yarn properties: low tensile strength
Good uniformity,high production rates
Application: yarns for knitting; terry yarns; weft yarns
Advantages: low manufacturing cost; possibility for automation; no fast-moving parts
Low energy expenses and low labor

The characteristics of a yarn are strongly dependent upon the properties of the fibers used in the yarn, but they are equally dependent upon the structure of the yarn itself. The following factors are especially significant: the number of fibers in the yarn cross-section fiber disposition fiber alignment position of the fibers in the strand (e.g. long fibers inside, short outside) binding-in (fully or only partly bound-in)

overall structure Twist

iv).Air jet spun yarn:

Air-jet spinning is a pneumatic method which consists of passing a drafted strand of fibers through one or two fluid nozzles located between the front roller of a drafting system and a take up a device.

The air-jet spun yarn consists of an untwisted core of parallel fibers and a surface wrapping of fibers. The core fibers account for approximately 85-95% of the yarn mass. The surface wrapper fibers are helical in nature unlike the wrapper fibers in the rotor yarn. The wrapper fibers are not uniformly distributed over the length; sometimes they are more on the surface and sometimes very few are on the surface.

The tensile strength is lower than that of rotor and ring yarns. More wrapping turns give better yarn strength, but at the same time higher wrapping frequency leads to higher bending rigidity and lower compressive softness.

The production rate of air jet/vortex spinning is 3-5 times higher than rotor spinning and 10-20 times that of ring spinning and, like rotor spinning, air-jet spun yarn is a lot cheaper to produce as it also uses fewer production stages. As is the case with rotor spun yarns, air jet yarns are more even, but weaker and have a harsher feel than ring spun yarns. Airjet spun yarns are mainly produced in the medium count (30 Ne, 20 tex) range and are mainly polyester/cotton blended yarns. End uses include woven sheeting and knitted lightweight shirting.

Number of fibers in the yarn cross-section

This determines, among other things, strength, evenness, handle, insulating capacity, thread-breakage rate, and the spinning limit of the raw material. Accordingly, there are lower limits to the number of fibers in the cross-section, as follows (for normal conditions):

Woolen (American English) or woollen (Commonwealth English) is a type of yarn made from carded wool. Woolen yarn is soft, light, stretchy, and full of air. It is thus a good insulator, and makes a good knitting yarn.The process creates a less than perfect yarn as compared to one that is spun with the worsted method. You will find that woolen yarn is fluffier, often has varying degrees of thickness, and creates warm, soft knitwear.Woolen yarns are not very strong, though plying can improve its strength.
Worsted: Worsted is a high-quality type of wool yarn, the fabric made from this yarn, Worsted wool fabric is typically used in the making of tailored garments such as suits, as opposed to woollen wool, which is used for knitted items such as sweaters. The essential feature of worsted yarn is straight, parallel fibres. Originally, long, fine staple wool was spun to create worsted yarn;

Filament yarn

It consists of filament fibres (very long continuous fibres) either twisted together or only grouped together. Thicker monofilaments are typically used for industrial purposes rather than fabric production or decoration. Silk is a natural filament, and synthetic filament yarns are used to produce silk-like effects.

Continuous filament yarns are produced either by combining the required number of filaments together or, more commonly, by producing the required number of filaments and thickness of filaments simultaneously in one spinning operation, as in the case of man-made fibers.

Mono filament yarn: They are simply single filament of synthetic fibers that are strong enough to be useful without being twisted with other filaments into a yarn.

Multi filament yarns: Consists of many filament with or without twist.

Texturized yarns are made by a process of texturizing filament yarns which combines multiple filament yarns into a yarn with some of the characteristics of spun yarns.Manufactures by Disc type,Stuffer box ,Air vortex, knit-deknit methods

Other Types of Yarn:

Twist less Yarn

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

Twist less Yarn

Core Yarn

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

Self Twist Yarn

Self-twist yarns are two-ply yarns Produced in a single operation. Each component is twisted in alternating directions in short segments.The two components are subsequently put together in such a way that they twist together (self-twist) to form final yarn.

Folded or Plied Yarn

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

Fancy yarns or novelty yarns:

A fancy yarn can be defined as one that differs from the normal construction of a single or doubled yarn by deliberately introduced irregularities in its construction.

The ‘novelty’ or ‘fancy’ yarns produce different textures and effects in the fabrics. Fancy yarns can be made from all natural fibers, all man-made fibers and their blends. They can be produced from pre-dyed or un dyed fibers and yarns.

Fabrics containing fancy yarns are used for many textile purposes, for instance apparel such as dress fabrics, or household textiles such as curtains and upholstery.

Using one or more of the following techniques, novelty yarns may be produced.combination of different fiber types; combination of different colours of yarns;combination of different yarn linear densities; combination of different yarn lengths.

Novelty yarns include a wide variety of yarns made with unusual features, structure or fiber composition such as slubs, inclusions, metallic or synthetic fibers, laddering and varying thickness introduced during production. Some linens, wools to be woven into tweed, and the uneven filaments of some types of silk are allowed to retain their normal irregularities, producing the characteristic uneven surface of the finished fabric. Man-made fibres, which can be modified during production, are especially adaptable for special effects such as crimping and texturizing.

From top to bottom: Regular yarn, braided yarn, ladder yarn and ribbon yarn

BASIC FANCY YARN

Generally, fancy yarns contain two or more of the following : a base or core yarn , around which the yarn intended to create the fancy effect is wrapped; the effect yarn , which forms

High-temperature sewing threads[

High temperature sewing threads provide durability and resistance to extreme temperatures. Some threads can be used for applications up to 800 °C (1472 °F). There are a variety of different sewing threads available which have different applications and benefits.

Kevlar-coated stainless steel sewing threads have a high-temperature and flame-resistant steel core combined with Kevlar coating designed to facilitate easier machine sewing. The stainless steel core has a temperature resistance of up to 800 °C (1472 °F) and the Kevlar coating is heat-resistant up to 220 °C (428 °F).

PTFE coated glass sewing threads have an excellent temperature resistance combined with a PTFE coating to provide easier machine sewing. The glass core has a temperature resistance of up to 550 °C (1022 °F) and the PTFE coating is heat-resistant up to 230 °C (446 °F).

Nomex sewing threads are inherently flame-retardant and heat-resistant with a tough protective coating which resists abrasion during the sewing operation. It is temperature resistant up to 370 °C (698 °F).

Bonded nylon sewing threads are tough, coated with abrasion resistance, rot proofing, and have good tensile strength for lower temperature applications. They are temperature-resistant up to 120 °C (248 °F)

Bonded polyester sewing threads are tough, coated with abrasion resistance, rotproofing, and have exceptional tensile strength for lower temperatures but heavier-duty sewing operations. They are temperature-resistant up to 120 °C (248 °F)

Electrically conducting yarn

An electrically conducting yarn is a yarn that conducts electricity. Conducting yarns are used to manufacture carpets and other items that dissipate static electricity, [1] such as work clothes in highly flammable environments, e.g., in the petrochemistry industry.

There are several methods known to manufacture electrically conductive textiles. The simplest way is to incorporate metal wires or wire meshes into fabrics. Another approach is to use metalized yarns. In staple yarns, it is possible to spin short strands of regular yarns with metal yarns. Electrically conducting yarns may be made of a central metal strand with regular yarn woven around it. [1]

An altogether different approach involves yarns based on conductive polymers, such as polyaniline.[2]

Electrically conductive yarns can also be produced from carbon nanotubes (CNT).[3] [4] Individual CNT-based fibers are spun (wet spinning) into a fiber directly from a solution. The solution either contains pre-made dissolved CNTs or the combination of chemicals required to synthesis CNTs. Tens to hundreds of individual fibers can be woven into a yarn. CNT-based yarns find applications in energy and electrochemical water treatment and can replace copper windings, e.g. in motors, which would improve the efficiency and consequently reduce the use of energy.

YARN NUMBER

Definition: Count is the numerical expression which express/indicates coarseness or fineness of yarn and a definition of yarn count is given by textile institute “count a number indicating the mass per unit length or the length per unit mass of yarn”

System of yarn numbering

Indirect system
Direct system

1.Indirect system:

In this system the count is the number of units of length per unit of weight of yarn. In this case higher the count, finer is the yarn. This system is generally used for cotton, woolen, worsted linnet.

English system: (Ne) The yarn number or count is defined as the number of hanks 840yds per pound.
Metric: (Nm) It is defined as the no of hanks (1000m)per kg
French count: (Nf) It is defined as the no of hanks (1000m)per 0.5 kg of yarn
Worsted: It is defined as the number of hanks(560yds) per pound.
Direct system: In this system the count of the yarn is the number of units of weights per unit length of yarn. This system is used for jute silk and synthetic etc.
Tex system of yarn numbering is called as universal system. This is direct system of yarn numbering and introduce by international standards organization.

Count in different system:

Tex: Count in the tex system is the weight in grams of 1000m or 1 km of yarn
2.Denier: The count in the denier system is the weight in gms of 9000m or 9km of yarn.
Decitex:The count in the denier system is the weight in gm of 10,000m or 10km of yarn.

BLENDING:

i) Definition:

Blended fabrics are created when two or more different kinds of fibers are mixed together to create a new fabric with unique properties Or A yarn or fabric made from two or more different fibers. These blended fibers are found in each of the yarn in the fabric.

Blend: Blend is the combining of different fibers together intimately to achieve a desired product characteristic. Blend can influence coloring, strength, softness, absorbency, easy care, resistance to wrinkling, ease of spinning, cost, etc.

ii) REASONS FOR BLENDING:

To improve the wear performance of the fabric.
To achieve aesthetic qualities i.e. appearance, texture and drape.
To obtain cross-dyed effect.
To improve spinning, weaving, dyeing and finishing efficiency.
To achieve on economic savings.
For producing permanent pleated fabrics.
To get resistance to moth and mildew.
For comfort and ease in washing, easy care.
Resistance to chemicals.
Improving absorbency.

iii) TYPES OF BLENDS

Types of blends and their advantages are as follows:

Polyester/Cotton:

Crease Resistance
Comfort
Less ironing

Linen/silk:

Crease Resistance
Lustre
Durable
Drape better

Spandex/Cotton:

Stretchy
Durable
Absorbency

Cotton/Polyester/Rayon:

Strength
Shine
Softness
Resilience
Comfort

Wool/Polyester:

Warmness
Breathable
Strength
Drapability

Cotton/Rayon:

Absorbency
Durability
Smoothness, shininess
Comfort
Cool effect

Rayon/Polyester:

Strength
Crease resistance
Comfort
Durability
Absorbency
Uniformity

Linen/Cotton:

Strength
Lustre
Wrinkle resistance
Comfort
Durable

iv) ADVANTAGES OF BLENDED FABRIC:

Fibres are blended to get the properties of these two fibre. E.g. Cotton/polyester. Cotton provides the absorbency and polyester provides strength.
Blending is done to produce a fabric which is very costly. E.g. Silk can ne blended with cotton or polyester.
Blended also helps to provide the fabric light weight with all desirable characteristics. E.g. Improving spinning weaving, and finishing efficiency and the uniformity of product.
To improve appearance of the fabric.
To improving functional as well as aesthetic properties properties.
Improve handle of fabric.
Improve profitability of a fabric making in cheaper to produce.

v) DISADVANTAGES OF MIXING & BLENDING

Sometimes some fibres may be hard and may cut the other softer fibre which may effect durability.
The manufacture may face some problem with, which fibres to blend and in what proportion to blend.
For blend there can’t be a general procedure for care, it will depend upon the particular fibre and finish applied to it. E.g. Cotton/wool can’t be washed with alkaline soap.
It may be difficult to get a uniform blend of the fibre in yarn because of different in specific gravity, length, diameter, surface, shape, lustre of the fibre.

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