Yarns

Presented by T. Srivani, Asst. Prof., FP

YARN DEFINITION: The word yarn or thread is used in common parlance to cover all the linear textile structures. Yarns can be either “single” or “folded”. “A yarn is an assemblage of fibres or filaments having a substantial length and relatively small cross section, with or without twist, being the end product of a spinning and winding process” Assemblies of fibres or filaments which are intermediate products in a spinning process are given special names such as Sliver, roving, bave, top or tow, depending upon the process and the particular intermediate stage.

CLASSIFICATION OF YARNS YARNS SINGLE YARNS

ASSEMBLED YARNS

FANCY YARNS

SPUN YARNS

FOLDED YARNS

FANCY YARNS

FILAMENT YARNS

ROTOR YARNS

FLAT FILAMENT YARNS

RING YARNS

TEXTURED FILAMENT YARNS

WORSTED YARNS

SEMI-WORSTED YARNS

WOOLLEN YARNS

BICOMPONENT

TAPE OR SPLIT FILM YARNS

Yarn may be any of the following • Number of fibers twisted together • Number of filaments without twist • Number of filaments twisted with more/less twist • Single filament • One or more strips cut by length of a sheet of material of natural/ synthetic or any polymer

TERMS SPUN YARNS are made by mechanical assembly and twisting together (spinning) of Staple fibres such as cotton, flax, wool, spun and noil silk, broken or cut man-made fibres FILAMENT YARNS are made by the assembly of continuous filaments, made from silk or man-made fibres A MULTI FILAMENT YARN is a filament yarn made from multiple filaments, assembled with or without twist. A MONO FILAMENT YARN consists of only a single continuous filament from man-made source.

Two or more yarns which are wound side by side on to same package, but without twisting around each other, are called ASSEMBLED YARNS. FOLDED OR PLIED YARNS are yarns made by twisting together Two or more single (and/or folded) yarns of the same or different types. Ex: 2 Ply (two singles) CORDS OR CABLED YARNS are yarns made by twisting together Two or more ply or folded yarns of the same or different types. Ex: 2,3 Ply Cord

Twist Direction Twists or turns per inch Twist Factor (K)

Spun & Filament yarns

Properties of Spun, Filament and Combination Yarns: 100%Spun Yarns: Warmth, Softness, Light Weight Ideal for T-Shirts, Sweaters and Blankets 100%Filament Yarns: Smoother, Finer and Lustrous Ideal for linings Combination of spun and filament Yarns: Durable, Easy care, Comfortable Suitable for more applications

Twist • The purpose of twist is to hold the staple fibers together • The twist could be used in different ways to embed different qualities to the yarn • A yarn that is twist balanced will not tend to curl • The direction of twist is also important for further designing as this can be used well by designers

Yarn twist parameters: Amount of twist is designated as TPI –turns per inch, which Affects appearance and durability of the yarns.

Spun yarn:

Low twist (2 to 12 tpi)

Soft twist yarns ex: Knitting

flexible fluffier soft

High Twist (20 to 30 tpi)

Hard twist yarns ex: weaving

smooth firm stronger

Filament yarns: Usually low twist (1/2 to 1 tpi)

Pebbly and harsh surface Crepe fil. with crepe twist

Twist Direction Twist can be inserted in either of two directions. S-Twist: Spirals run upward to the left (clock wise) Z-Twist: Spirals run upward to the right (anti clock wise) Combination of S and Z twist: to produce crepe fabrics

The majority of the single yarns are twisted in Z direction S-twist is considered as a reverse twist by the spinner Direction of twist has no effect on single yarns Normally the folding twist is in the opposite direction to that of the single yarns. Balanced twist is when the folding twist is approximately equal and opposite to the singles

Twist factor The angle of twist is the factor that determines how the yarn will behave. Yarns with a low twist level have a lower angle of twist, and will be relatively soft, bulky yarns Yarns with higher twist angles will be strong, lean and hard yarns Over twisted yarns will have very high twist angles; They will be very hard, weaker and snarl easily

Typical twist factors: Short staple end use

Tex twist factor

Doubling weft Ring weft Ring warp Voile Crepe Rotor

2900-3200 3200-3500 3800-4300 4900-5300 5700-7700 3700-4700

Twist factor Tan ө = Пd l l= 1 /turns per unit length d= /¯yarn tex Therefore, tan ө = turns per unit length X /¯yarn tex Turns per unit length = K/ /¯tex Twist factor = turns per inch / /¯cotton count

Twist and Handle • A soft twisted yarn will give a fuzzy texture. • A high twisted yarn will increase the surface roughness and increase the grainy texture according to the bulkiness. • The direction of twist and when they are combined may give interesting effects.

Twist and Bulkiness • The bulkier the yarn, lesser the twist. • Finer the yarn higher the twist. • Bulkier yarn needs lesser twist and so it has lesser strength. • Finer yarn has more twists and strong. • But when the twist is increased after particular point the strength is reduced due to the breakage of the fibers.

Blends / Mixtures • A blend is a combination of two materials at fiber stage. • A mix is two materials put together at a later stage as strands. • The texture we get is different from each of them. • The design value of these are high.

Need • The need for blends or mixes are. – – – –

Cost. Different quality that each fiber offers. More effective usage of the materials. The necessity of different and in between qualities and both the qualities.

Design Values • The design values of such blended and mixed yarn can be explored to give an innovative look to the textile • More innovative processes can be explored • The design can happen from yarn stage.

Fancy Yarns • Fancy yarns are explorations of the prior said attributes such as • Twist • Bulkiness • Color • Material – Blends and Mixes – Material(conventional/non-conventional)

Varieties • • • • • • • •

Boucle Loop Gimp Nep Chenille Corkscrew Core spun Metallic

Physical properties and performance characteristics of different yarn types: Yarn type

General yarn properties

Staple yarns

Excellent Handle Good covering power Good comfort rating Reasonable strength Reasonable uniformity

• Carded cotton • Combed cotton • Woollen • Worsted • Linen

Yarn type

General yarn properties

Continuous filament yarns

Excellent uniformity Excellent strength Can be very fine Fair handle Poor covering power

•Natural •Non-synthetic •Synthetic

High bulk yarns • Staple • Continulous filament

Light weight Good covering power Good loftiness and fullness

Stretch yarns Continuous filament

High stetchability Good handle Covering power

Special end use: •Tyre cord •Rubber •Core yarn •Cabled •Split film yarn

Purely functional Designed to satisfy a specificset of conditions

Novelty yarns: Excellent decorative features •Fancy yarns •Metallic

Variables in yarn production Type of fibre or filament Dimensional and physical characteristics of the fibre/filament Mechanical properties of the fibre / filament General properties Yarn production systems Components of the yarn and percentages Linear density and level of twist Yarn construction Texturisation and method of texturisation