What are yarn twist and twist coefficient?

1. Twist: The number of twists per unit length of yarn.

1.1 Special twist system: Tt = number of twists per 10 cm. (Cotton-type yarn)

1.2 British twist system: Te = number of twists per inch. (Cotton-type yarn)

1.3 Metric twist: Tm = number of twists per 1 meter. (Fine-spun wool yarn and synthetic fiber filament yarn)

Note: The twist calculated theoretically is the calculated twist; the twist measured on a twist meter is the actual twist.

To compare the degree of twist between yarns of different thicknesses, the concept of twist angle is introduced.

2.Twist Coefficient  

Due to the effect of twisting, the angle between the surface fibers of the yarn and the yarn axis is referred to as the twist angle. Since measuring the twist angle is inconvenient, the twist coefficient is generally used in practical applications.  

1.1 Count System: α_t = T_t × √T_t (α_t is the twist coefficient in the count system, and T_t is the twist in the count system)

2.1 Metric Count System: α_m = T_m/√Nm (α_m is the metric twist coefficient, T_m is the metric twist)

3.1 Imperial Count System: α_e = T_e/√Ne (α_e is the imperial twist coefficient, T_e is the imperial twist)

3. Factors Affecting Twist Coefficient: The magnitude of the twist coefficient of yarn is primarily determined by the properties of the raw material and the intended use of the yarn.  

3.1 Raw Material Properties: To achieve the desired strength, when spinning yarn from fine, long fibers, the twist coefficient can be lower; when spinning yarn from coarse, short fibers, the twist coefficient should be higher.

3.2 Application Factors:  

(1) Warp yarns require higher strength, so the twist coefficient should be larger;  

(2) For knitted outerwear fabrics made from lightweight, crisp fabrics, the twist coefficient should be larger to achieve a smooth, crisp, and crisp style and prevent pilling;

(3) For weft yarns and knitted yarns, which generally require softness and low torque, the twist coefficient should be lower;

(4) For woven and knitted pile fabrics, the twist coefficient should be lower to facilitate pile formation.

3.3 Yarn fineness: For fine-count or high-count yarn, the twist coefficient should be higher; for coarse-count or low-count yarn, the twist coefficient should be lower.

Common twist ratios for cotton-type yarns