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# Dry goods: linear density of fibers and yarns

Linear density is the thickness of fibers and yarns. It can be directly expressed by the cross-sectional diameter, cross-section perimeter, or cross-sectional area of fibers and yarns. When the cross-sectional shape is close to a circle, the diameter is used to indicate the thickness, and it is measured in micrometers or millimeters. However, the cross sections of fibers and yarns are generally not regular and thin. The diameter or cross-sectional area must be measured one by one under the microscope using an eyepiece micrometer and an objective micrometer, or on a microscope projector. Testing and testing are time-consuming and laborious. Moreover, the thickness and thickness of fibers and yarns are uneven. The average diameter of the cross section is used as the linear density index, which may affect the evaluation results. Because length and weight tests are more convenient, the relationship between length and weight is often used in production to indirectly express its thickness. That is, the indirect index is used to indicate the linear density of fibers and yarns. The indirect indicators of linear density are divided into fixed length system and fixed weight system.

I. Fixed length system

The fixed length system refers to the weight of a fiber or yarn within a certain length. A larger value indicates a thicker fiber or yarn.

(1) Ttex

Tex is an international unit of measurement of linear density. It is also the legal unit of measurement of linear density in China. It is defined as the weight in grams (milligrams) of a 1000m (mm) long fiber or yarn at a given moisture regain. Its unit is tex. Calculated as follows:

Ttex = GK × 1000 / L

In the formula: Ttex——the linear density of the fiber or yarn (tex); L——the length of the fiber or yarn (m or mm); Gk——the public weight of the fiber or yarn (g or mg). In addition, when expressing the linear density of fibers.

It is often expressed in decitex (dtex). Dtex refers to the weight in grams (mg) of a fiber or yarn of 10,000 meters (millimeters) long at a given moisture regain. One decitex is one tenth of a tex.

Tex is used to indicate the linear density of all fibers and yarns. The larger the tex value, the thicker the fibers and yarns.

(B) Denier Ndem (fineness)

Denier is defined as the weight in grams (milligrams) of a 9000 m (mm) long fiber or yarn at a given moisture regain. Its unit is denier (den or D), and the calculation formula is as follows:

Nden = GK × 9000 / L

In the formula: Nden-the linear density of the fiber or yarn (den or D); L-the length of the fiber or yarn (m or mm); Gk-the public weight of the fiber or yarn (g or mg).

Denier is also called fineness, which is usually used to indicate the linear density of chemical fibers and silk. Higher denier values indicate thicker fibers and yarns.

Second, fixed weight system

Fixed weight is the length of a certain weight of fiber or yarn. The larger the value, the finer the fiber or yarn.

(1) Metric system (Nm)

It is defined as the length (meters or millimeters) of a unit weight (gram or milligram) of fiber or yarn at a given moisture regain. Its unit is branch and the calculation formula is as follows:

Nm = L / GK where:

Nm——the linear density of fiber or yarn (count); L——the length of fiber or yarn (m or mm); Gk——the public weight of fiber or yarn (g or mg). Metric count is usually used to indicate the thickness of cotton fiber, wool yarn, linen yarn, and spun yarn. The larger the value, the finer the fiber and yarn.

(2) British system count (Ne)

Cotton yarn imperial count is defined as a multiple of 840 yards in length for a pound of cotton yarn at a specified moisture regain (imperial). Its unit is English branch and the calculation formula is as follows:

Ne = L / 840 × Gk

In the formula: Ne——the linear density of the fiber or yarn (British branch); L——the length of the fiber or yarn (yard); Gk—the nominal weight of the fiber or yarn (pounds).

Conversion between linear density indicators

(I) Conversion between indirect indicators

Conversion formula between denier and metric number: Ndem · Nm = 9000

Conversion formula between tex and metric count: Ttex · Nm = 1000

Turks and denier conversion formula: Ndem ÷ Ttex = 9

Conversion formula for inch count and tex number: Ne = 590.5 × (100 + Wmk) / (100 + Wek) × 1 / Ttex

Conversion formula for imperial counts and metric counts: Ne = 0.590 5 × (100 + Wmk) / (100 + Wek) × Nm

Wmk is the metric metric regain of the yarn (%); Wek is the metric metric regain of the yarn (%). The metric metric moisture regain of pure cotton yarns is 9.89%, and the metric metric moisture regain is 8.5%. The conversion formula between the imperial count and tex is Ne = 590.5 × (100 + 8.5) / (100 + 9.89) × 1 /Ttex=583.1/Ttex purified fiber yarn (including chemical fiber and chemical fiber blends), the metric moisture regain rate is the same as the British regain rate.

The imperial count of combed wool yarns refers to multiples of 560 yards in a pound of yarn at a given moisture regain. The imperial count of carded yarn refers to the number of multiples of 1600 yards in a pound of yarn (referred to as carded yarn nylon) at a given moisture regain, or the number of 300 yards in a pound of yarn at a nominal moisture regain. Multiples (called carded yarn kerts).