What is Yarn,Yarn Twist

What is Yarn?

Yarn is a long continuous length of interlocked fibres,suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery and rope making. Yarn can be made from any number of natural or synthetic fibers.

  

Yarn Twist:

Yarns  (specially  spun  yarns)  are  twisted  to  hold  the  fibres  together.The  number  of twists  perunit  length  is  used  to  measure  twist.  Yarn twist can be broadly divided by number of twists: none or very low, low, average, and high twist. Yarn twist impacts the yarn's appearance, fineness, strength, and absorption.

Twist Directions:

Fibres can be twisted together in the clockwise or counter clockwise direction to form yarns. Yarns are twisted in the clockwise direction for "S" twist, and counter clockwise for "Z" twist. The "Z" twist is employed in a majority of the spun yarns used for fabric construction. Depending on the direction of this final twist, the yarn will be known as S-twist or Z-twist.

Choosing Right Twist:

- Filament yarns used for smooth fabrics have no or very low twist.
- Yarns used for napping, bulky sweaters, and pile in towels have low twist.
- Most spun yarns used for woven fabrics have average twist.
- Crepe yarns used for plain and crepe weave fabrics have high twist.

How to measure yarn Fineness (Count, Number, Coarseness)?

Thickness of yarn is measured by count. Count is the numerical expression which defines yarn fineness/coarseness. It is also called as yarn number or linear density.
Several systems and units are used for expressing the yarn count-

1.    Indirect System: 

The numbers of unit length per unit weight. 
English count (Ne): Numbers of hanks of 840 yards in 1 Ib of yarn.
In this system, higher the count, finer is the yarn. If there are 10 hanks of cotton   yarn that weight one pound, this is 10 Ne yarn. Each of the hanks is 840 yards long, so the total length of the yarn is 8,400 yards. So, if it's a coarser yarn it will take fewer hanks, and less length to make up a pound. Used for cotton, wool, linen etc.

         Metric Count (Nm): Number of 1000 meters of yarn present in 1 kg of yarn.

        2.Direct system: 

            The numbers of unit weights per unit length. 

            Denier = Weight of yarn in grams present in 9000 meter or 9 km length.
           Mainly used for jute, silk etc.

2.    Universal System: 

Tex system is called universal system. This is a direct system and introduced by ISO.
Tex = Weight of yarn in grams present in 1000 meter or 1 km length.

Yarn Types & Classification:

Fibre length is used to broadly divide yarns into:

Spun/Staple yarn: 

Spun yarn is made by twisting or otherwise bonding staple fibres together to make a cohesive thread, or "single". Twisting fibres into yarn in the process is called spinning.

Filament yarn:

It consists of filament fibres (very long continuous fibres) either twisted together or only grouped together. These are two types-

1. Monofilament yarn: Made from a single, relatively thicker filament fibre.  Transparent  sewing  thread,  metallic  yarns,  bare  elastic,  and  fishing  lines  are examples of monofilament yarns. Silk is too fine to be used as a monofilament yarn.

2. Multi-filament yarn: It made from multiple filament fibres. Continuous filament fibre length requires little or no twisting to hold the multi-filament yarn together.

Simple Yarns:
They are characterized by uniform size and regular surface. They can be broadly divided into single, ply, cord, and rope yarns.
1. Single yarns: The simplest type of yarn. It is commonly produced by twisting together staple or filament fibres.
2. Ply/Folded yarns: Produced by twisting two or more single yarns. Each strand of single yarn is referred to as a ply. Thus, four single yarns twisted together would form a four-ply yarn.

3.Cord yarns: Produced by twisting two or more ply yarns.
4.Rope yarns: Produced by twisting two or more cord yarns.

Fancy/Novelty Yarns:

 
Typically made of two or more stands, are produced to provide decorative surface effects. Derivatives of novelty yarn are as follows-

Slub yarns: Can be either single or ply yarns. These yarns are characterized by the soft bulky area that is spun at regular or irregular intervals.

Flock/flake yarns: They have small tufts of different colored fibres added at intervals. These tufts can be easily pulled out. Flock/flake yarns are generally single yarns.

Nub, knot, and spotyarns: These are ply yarns in which the effect yarn is twisted round the base yarn to produce a thicker area or a bump.

Bouclé and loop yarns: These are ply yarns that use three sets of yarns - base or core yarn, effect yarn, and tie yarn. The effect yarn is looped around the base or core yarn and tied with a binder yarn.

Spiral and corkscrew yarns: These are ply yarns in which one ply is soft and thick and the other is fine.

Chenille yarns: Chenille yarns are pile yarns that are often made by slitting leno weave fabrics into narrow strips in the warp direction.

Textured Yarns:
They are  made  of  fully  drawn filament fibres  with  a  changedsurface,  shape  and  texture  developed  by  using  the  new  spinning techniques.  Nylon and polyester are two main fibres that are textured.
There are two main types of textured yarns:
1. Stretch yarns

2. Bulk yarns

Stretch yarn: Can be made by using any of the following methods:
1. By  using  special  heat  setting  treatment  to  thermo plastic filament fibres such as nylon and polyester .

2. From elastomeric fibres.

3. From bi-component fibres.

4. From bi-constituent fibres.

5. From chemically treated natural fibres.

Bulk Yarns:

These yarns are softer and much pliable then tightly constructed twisted yarns.  Bulk yarns also have a better cover. They create less transparent fabrics and are of two types:

1. High bulk yarns.

2. Loop-bulk or air-jet yarns.