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Quality Standard of Polyester Filament

Views:5026     Author:Site Editor     Publish Time: 2018-06-30      Origin:Site

Quality Standard of Polyester Filament

The quality index of polyester filament can be divided into physical index and appearance index.

1. Physical Index

A. linear density

Linear density is the index of filament thickness and the most basic quality index. It is generally expressed by (dtex), or by Tex (tex). The linear density of filaments includes complex filament density and single filament density. For example, the complex filament density of 167dtex-30F filament is 167dtexand the density of single filaments is 5.6dtex.

B. Breaking strength

Breaking strength refers to the external force by which the thread of a unit is broken. High fracture strength, in the processing process is not easy to break. But if the breaking strength is too high, the fiber rigidity increases, the yarn and the fabric handle become bad.

C. Elongation at break

Elongation at break refers to the elongation of the fiber when it is stretched to break. It is an index reflects the toughness of the fiber.

For clothing filaments, the greater the elongation, the softer the handle, the less the wool and the broken ends are during post-processing; when the elongation is too high, the fabric is easily deformed; generally, it is between 20% and 30%. For industrial filaments, the smaller the elongation, the less deformed the final product is, generally less than 14%.

D. Yarn evenness

The evenness of the strip is the index of the evenness of the filament. The cross is called the evenness of the strip, and the coefficient of variation (CV) is used to express the evenness of the strip. This index is particularly important for pre-oriented and drawing wires. If the filaments are uneven, it is easy to produce wool and dyed irregularity in the process of processing.

E. Boiling water shrinkage

Boiling water shrinkage is the ratio of the length of shrinkage of a specified length of filament to the original length after boiling in boiling water for a certain time. The shrinkage of boiling water is an index to reflect the heat setting degree and dimensional stability of filament, which is related to the dyeing property.

F. Dyeing uniformity

Dyeing uniformity is an important quality index of filaments and a reflection of the internal structure of filaments.

( 1 ) The dyeing uniformity of the deformed filament . The dyeing uniformity shall be determined for each yarn bobbin . After the deformation yarn is dyed with socks, the sample is compared with the standard color sample . The higher the number of stages , the more uniform the dyeing performance is . For example , Grade ≥ 4.0 are first-class goods, Grade ≥ 3.5 are second-class goods . If there is a flower on the sock , the highest can be classified as a second equivalent . If there is a star spot or a winding wire , it is reduced to the equivalent .

(2) The dyeing uniformity of stretch wire. If the dyeing average (grey card) / grade ≥ 4.0, as the first grade, ≥ 3.5 as a qualified product.

Dyeing uniformity in addition to stockings, but also can be used to determine the color of the instrument.

G. Crimp shrinkage and crimp stability

Crimp shrinkage and crimp stability are only applicable to deformed wire.

Crimp shrinkage rate refers to the ratio of the difference between the length of the stretch length measured under the specified load and the length of the pair in the straightening state and the length after straightening. It reflects the reversion of the crimped stereoscopic structure of the deformed wire after it is straightened. If the crimp shrinkage rate (%) of low elastic wire is (1830) ±5 as the top grade, and (1830) ±7 is the first grade crimp stability.

Crimp stability refers to the ratio of the crimp shrinkage of the deformed wire after increasing the load to that before increasing the load. It reflects the crimp shrinkage of the deformed wire that can be retained after being subjected to heavy load. For example, the crimp stability of low elastic wire above 70% is the top grade, and ≥ 55% is the first grade.

H. Oil length

The oil - containing rate is the index that reflects the oil content of the filament . During the processing, the polyester filament can be oiled , and the oil of the filament can make it have smoothness , bundling property and anti static property. For example , the oil - containing rate ( % ) of the polyester drafting silk ( 0.5 ~ 1.0 ) ± 0.3 is the top class, and ( 0.5 ~ 1.0 ) ± 0.35 is the first class.

I. Linear density coefficient of variation

The coefficient of variation of linear density ( CV value ) is an index reflecting the degree of the fineness and the uniformity of the filament . For example , the linear density of the polyester drafting filament is 76.0 dtex. And when the linear density variation coefficient ( CV value ) is less than or equal to 1.0,it means the top grade goods. And the linear density variation coefficient ( CV value ) is not more than or equal to 1.5 as an equal value . In addition to this , there is also a line density deviation rate reflecting the uniformity of the linear density , which reflects the fracture strength variation coefficient and elongation variation coefficient of elongation uniformity

2. Appearance Index

The appearance index can be checked by visual method. Polyester filament has many appearance indexes, such as wool silk, color and color, broken head, oil filaments, tail silk, cobweb silk, shaping, stiff silk and net weight of bobbin, etc. One of the most important is the silk and color.

A hair is a single filament in a filament. Wool yarn will often lead to breakage or roll, affecting normal production, and also having a great impact on post-processing.

The color index requires that the color of the whole package is normal, the color of the inner and outer layers is the same, and the color of the package is the same.



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