Classification of yarns

Yarns can be roughly divided into two categories: yarns imitated from short fibers and filaments composed of continuous filaments. According to the difference of fiber raw materials, the classification is as follows:

Yarn – short fiber spinning into yarn (cotton yarn, hemp yarn, wool yarn, spun silk, purified fiber yarn, blended yarn) – filament (silk, chemical fiber filament)

Recently, the new textile technology has developed core-spun yarns with long and short fibers.

How to make yarn

The production method of yarn varies with the length of the fiber raw material, and there are generally three types: spinning, reeling and chemical fiber spinning.

spinning

In order to make the messy short fibers into a continuous yarn, the following processes must be carried out:

①Taking cotton yarn as an example, first of all, the messy short fibers should be sorted into basically parallel fibers. For this purpose, the processes such as loose cotton bale, cotton cleaning, carding, and drawing frame are carried out, so that the fibers can obtain sufficient energy from the compressed packaging. The loose, mechanical removal of impurities, and gradually form a slender structure of fiber strips. ② After the fibers are arranged to a certain degree of parallel straightening, the fiber strips are stretched to a certain degree of fineness according to the requirements (referring to the thickness of the produced yarn). According to the requirements (referring to the thickness of the produced yarn), the fiber strips are stretched to a certain fineness, and a certain twist must be given at the same time to increase the saturation between the fibers, so as to obtain the required yarn.

At present, the process of producing yarn from short fibers is completed by machinery. In ancient times, our ancestors used fiber blocks as raw materials to produce yarn, and gradually extracted a small amount of fibers, and at the same time, twisted them to make yarn. This kind of manual spinning is used in Some remote areas may still exist.

silk reeling

For cocoons that are bonded to more than a few hundred meters, reeling is often used to make filaments. First, boil the cocoons in hot water at a certain temperature, so that the sericin part of the cocoon layer is dissolved and swelled, and the effect of the cocoon layer is relieved. Bonding, and then drawing several cocoons together as required to obtain filaments of a certain thickness, as shown in the figure

The chemical fiber filament is processed from the monofilament drawn from the chemical fiber stock solution through the spinneret hole.

twist and twist

During the spinning process, the fiber sliver is rotated and twisted to make the fibers hug each other to form a yarn, which is called twisting. Short fibers must be twisted; although filaments are not twisted during processing, there is also a slight twist due to high-speed winding.

Twist is the number of twists per unit length of yarn (one twist is 360°), which is one of the indicators indicating the degree of yarn twisting. So the twist is:

Twist (r/m) = number of turns ⭕ (number of 360°) ÷ length

Usually, the unit of the yarn L of the short fiber is “10 cm”, which is represented by Tt and Tm, respectively.

The degree of twist has a great influence on the thickness, strength and abrasion resistance of the fabric. In wool fabrics, twist has a great influence on hand feel and style, so twist design is often regarded as an important part of fabric design. Common twist values ​​in spinning process are shown in the table.

Yarn twist Yarn name Twist (r/m) Weak twist yarn 300 or less

Medium twist yarn 300~1000

Strong twist yarn 1000~3000

Strong twist yarn above 3000

According to the difference of the rotation direction, there are Z twist and S twist, as shown in the figure.

Figures (1) and (2) show that the warp and weft yarns adopt different twisting positions. From the surface of the fabric, the warp and weft yarn fibers are inclined in the same direction, so that the surface of the fabric is reflective and glossy. At the interlaced contact of warp and weft yarns, lubricant for textile, the inclination direction of the fibers is almost vertical, but not close to each other, so the fabric appears bulky and soft;

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As shown in Figures (3) and (4), the warp and weft yarns adopt the same twist direction. It can be seen from the surface that the warp and weft fibers are inclined vertically. At the contact point of warp and weft, the inclination direction of the fibers is almost the same, and they are embedded with each other, so the fabric is thinner and the body is relatively thin. Good, the weave points are clear, the fabric is higher than the former, but the fabric luster is not as good as the fabric with different warp and weft twist directions.

Worsted wool fabrics and fabrics made of chemical fiber medium and long fibers are often arranged with several S twists and Z twists.

Definition of Yarn Related to Twisting

single yarn

Yarn spun from short fibers is called single yarn, usually with Z twist.

The strand is made of two or more yarns twisted together, and the twist direction of the twist must be opposite to that of the single yarn.

According to the different ways of merging, the strands can also be divided into single-twisted strands and multi-twisted strands. Single twisted strands are directly made from single yarns. The double-twisted strand is formed by twisting two or more single-twisted strands, and the twist direction of the double-twisted strand is opposite to that of the single-twisted strand. The twist direction of the strands is indicated by the letters ZS or SZ. The first letter is the twist direction of the single yarn, the second letter is the twist direction of the single twisted strand, and the third letter is the twist direction of the double twisted strand.

In the figure, the single yarn is Z twist, the twist direction of the single twist is S, and the twist direction of the double twist is Z.