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Types of Fabrics with Respect to Different Types of Twist
2022-06-08
Twist Directions:
Twist may be performed in the following two directions known as S (clockwise) and Z (anticlockwise) twists (Figure-3). These S and Z twist are described below.
S-twist:
When a twisted yarn is held vertically and the individual filaments appear as the diagonal in the letter “S,” then it is called an “S–twist.” Similarly, when several yarns are combined and given an S-twist, then the individual yarns appear as the diagonal in the letter “S.”
n another way, a single yarn has ‘S’ twist if, when it is held in the vertical position, the fibers inclined to the axis of the yarn conform in direction of slope to the central portion of the letter S. S and Z twisted yarns are shown in Figure-3.
Z-twist:
When a twisted yarn is held vertically and the individual filaments appear as the diagonal in the letter “Z,” then it is called a “Z–twist.” Similarly, when several yarns are combined and given a Z-twist then the individual yarns appear as the diagonal in the letter “Z.”
In another way, a single yarn has ‘Z’ twist if, when it is held in the vertical position, the fibers inclined to the axis of the yarn conform in direction of slope to the central portion of the letter Z.
As can be seen from the diagram of twist directions (Figure-3), by holding the yarn upright, the slope of the middle of the yarn should flow in the same direction as the slope of the middle of the letters S or Z. The majority of single yarns are Z, but the direction does not really affect the property of the yarn. However, in a plied yarn, the direction is important because the single yarn should be in one direction but when two yarns are combined to make the ply it is running in the opposite direction; this ensures that the yarn holds together.
For example, 2 x S single yarn + Z ply = stable, smooth, firm, tight and durable yarn suitable for weaving; worsted yarns often possess a high-angled twist.
2 x Z single yarn+ S ply = stable, soft, bulky yarn suitable for knitting. It often has a low-angled twist.
2 x S single yarns + S ply = an unstable yarn that will snag and curl.
2 x Z single yarns + Z ply = unstable yarn that will snag and curl.
The amount of twist added into a yarn will determine the property of the yarn in terms of durability, flexibility, resilience and strength. A high-twist yarn may offer a hard and relatively stiff yarn, whereas a low-twist may give a weak yarn that is more flexible. Finer yarns have more twists in them than coarser ones, and warp yarns have more twists in them than weft yarns. Fabrics with a soft surface, e.g. peach effect, have a slack twist called soft-twist, which allows fiber ends to be pulled to the surface. Fabrics with smooth surfaces have a higher amount of twist, which offers extra strength and some crease resistance, whereas textured surface fabrics, such as crêpe, are given a maximum twist.
Types of Fabrics with Respect to Different Types of Twist:
Soft surfaced fabrics have slack twist:
- Smooth surfaced fabrics have optimum twist. This stimulates strength, smoothness, and elasticity.
- Crepe fabrics have the maximum number of twists.
- Poplins have two single yarns that are Z-twisted individually and plied together using an S-twist.
- Sewing thread has three S-twisted single yarns, which are then Z-twisted together. Tear-resistance of this thread will be higher.
Previous:Effect of Twist on Yarn Strength
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