Twist coefficient twist cannot be used to compare the twist degree of different thicknesses of yarns, because thicker strips of yarn have a greater inclination than thinner strips of yarn with the same twist. In the actual production, the twist coefficient is often used to represent the twist range of the yarn. Twist coefficient is the relative value of yarn twist degree combined with thread density, which can be used to compare the twist degree of different thicknesses of yarns. The twist factor can be calculated according to the twist of the yarn and the linear density of the yarn.

Twist direction The twist direction refers to the inclination of the single yarn in the fiber or strand after the yarn is twisted. There are two kinds of Z-twist and S-twist. After twisting, the twist of the yarn is inclined from the lower right corner to the upper left corner, and the tilt direction is consistent with the middle of the "S", which is called S twist or smooth twist; The twist of the yarn from the lower left corner to the upper right corner, and the tilt direction is consistent with the middle of the "Z" is called Z twist or backhand twist. Generally, single yarn is often used Z twist, and strand is used S twist.

The twist direction of the strand is always indicated by the successive twist. For example, a strand with a single yarn of Z twist, an initial twist of S twist, and a double twist of Z twist has a twist direction expressed by ZSZ.

The twist direction of the yarn has a great influence on the appearance and feel of the fabric. By using the twist direction of the warp and weft yarn to cooperate with the fabric organization, the fabric with different appearance and feel can be woven.

Hygroscopic textile fibers placed in the air, will continue to exchange water vapor with the air, that is, textile fibers continue to absorb water vapor in the air, but also continue to release water vapor into the air. The performance of textile fibers in absorbing or releasing water vapor is called the hygroscopic property of fibers.

The hygroscopicity of textile fiber is one of the important physical properties of textile fiber. The size of textile fiber hygroscopicity has a certain impact on the shape size, weight, physical and mechanical properties of textile fiber, which also affects its processing and operational properties. The moisture absorption capacity of textile fiber also directly affects the wearing comfort of the fabric. The fiber with large moisture absorption capacity is easy to absorb the sweat discharged by the human body, regulate the body temperature, and relieve the sense of dampness, thus making people feel comfortable. So in the commercial trade, fiber performance test, textile processing and textile selection should pay attention to the fiber hygroscopicity.

In the common textile fibers, wool, hemp, viscotic fiber, silk, cotton flowers and other moisture absorption ability is strong, synthetic fiber moisture absorption ability is generally poor, of which vinylon and nylon moisture absorption ability is slightly better, acrylic fiber is worse, polyester is worse, polypropylene and chlorine fiber is almost no moisture absorption. At present, synthetic fibers with poor hygroscopic ability are often blended with natural fibers or viscose fibers with strong hygroscopic ability to improve the hygroscopic ability of fabrics.

In the hygroscopicity of fiber, in addition to hygroscopicity, the water absorption of fiber materials is also closely related to the wearing comfort of the fabric. The water absorption of fiber refers to the fiber's ability to absorb liquid water. The water vapor and sweat generated by people during activities, the moisture absorption and water absorption properties of the main ** * material, absorb and radiate outwardly, so that people feel comfortable. Generally speaking, the coat is mainly soaked by rain, so the fiber with small water absorption can be selected as the coat material; Underwear is mainly soaked by the body's inexplicit evaporation and sweating, so it is necessary to choose fiber with large moisture absorption and water absorption as underwear materials.