Twisted yarn combines multiple fibers, threads, or yarn to wrap around (twisting) motion. For example, twisting fibers will create a thread (or single), twisting threads will create a yarn, and twisting yarns will create a cord or cable - and so on.
The twisted yarn process is when one end of a fiber strand is held and the other end is turned back to form a yarn.
For staple fibers, twisting is necessary to turn the fibers into yarns. Before twisting, the
loose fibers usually coalesce into a fiber strip.
After twisting, the outer fibers are squeezed towards the inner layers to create centripetal pressure, which causes the strand to gain friction along the direction of the fiber elongation.
Twisting creates a compact structure that is not easily damaged by lateral external forces, and twisting also creates deformed filaments and fancy threads for filament yarn and ply yarn. In addition, the amount and direction of the twist affect the feel and appearance of fabrics and their intrinsic quality.
After twisting, the outer fiber is twisted back in an inclined spiral. The fiber is twisted and deformed. Yarns are held together, changing the fibers' collective structural form and mechanical and physical properties.
Twisted yarn can be classified into 2 types depending on the twisting direction.
- S twisted yarn is the left twisted
- Z twisted yarn is the right twisted
The portion of fibers on yarns indicates where the yarn is S or Z twist. The regular weaving industry usually used a Z twisted yarn. The twisting direction may observe by holding yarns in a vertical position. If the twisting direction of the slope of the center part of the letter “S”, the yarn has an S twist. If the yarn spiral conforms to the letter “Z” slope, the yarn has a ‘Z” twist.
2 sections of the yarn produce an angular displacement of 360°, which becomes a twisting round, commonly referred to as one turn.
Yarns are generally twisted in the Tex system, expressed as the number of twisting rounds per 10cm of yarn length. For combed woolen yarns and chemical filaments, use the metric count system, expressed as the number of twisting rounds per meter. In addition, there is the English count system, defined as the number of twisting rounds per inch.
The twisted affects the yarn's strength, flexibility, elasticity, and shrinkage. If the twisted increases, the strength of the yarn would be increased, but the twist must not exceed a particular value. Otherwise, the strength decreases, which is called the critical twist of the yarn. The critical twisted is different for yarns made from different raw materials. In general, as long as the strength requirements are met, the less twist the yarn has, the better, because an increase in the twisted makes the yarn stiffer to the touch, less elastic and more shrinkage. This is the reason why filament yarns are twisted as little as possible.
Most fabrics are made with ordinary yarn twisted. This is the amount necessary to hold the fibers close enough together to prevent them from slipping apart. Thus gives strength to the yarn.
The number of twists per inch can measure the number of twists.
Low twisted – 0 to 3 twisted per inch
Ordinary twisted – 4 to 7 twisted per inch
High twisted – 8 to 12 twisted per inch