Small knowledge 丨 Knitted fabric garments - Twisted rate test method after washing. No. 315

The more important standards for knitted products, "knitted sportswear" and "knitted T-shirts", were added to the post-washing distortion rate assessment index in the second revision in 2002, and were retained for the third revision in 2009. The assessment of indicators, other knitting standards developed and revised in succession FZ/T73020-2004 "Knitted Casual Wear", FZ/T73021-2004 "Knit Student Wear", etc. also regarded the project as the assessment content. It can be seen that the distortion rate after washing has become knitting. A routine assessment item for the product. However, since the distortion rate after washing is a newly added assessment project in recent years, there are some unreasonable aspects from the test method to the assessment standard, which needs further improvement.

1. Analysis and suggestion of test method for distortion rate after washing

The twisting rate after washing is an index to measure the degree of skew of the top of the garment or the side seam of the trousers after washing with water. The test steps mainly include the measurement and calculation after washing and washing.

 

1.1 Washing procedure

 

The washing procedure for testing the twist rate after washing is the same as the washing procedure for testing the dimensional change rate of the washing. The standard clearly specifies the washing rule: the ready-to-wear ratio of the washed dimensional change rate is used to measure the twist rate after washing (ie, without using another sample) Washing), washing size change rate washing procedure is carried out according to 5A of GB/T8629, and the number of washing pieces is 3 pieces (the number of knitted sportswear standards is not clearly cleaned).

 

1.2 Measurement after washing

The measurement of the distortion rate after washing is shown in the figure below, and the side with the largest degree of skew of each garment is measured, and the average of the distortion rates of the three samples is taken as the result.

See Figure 1 and Figure 2 for the test position of the distortion rate after washing .

1.3 Calculating the distortion rate

The calculation of the distortion rate after washing is shown in formula (1):

Where: F—distortion rate, %;

a-Top: the distance between the side of the upper side of the jacket and the seam of the sleeve and the point of the side of the seam and the intersection of the side seam and the bottom of the bottom;

Pants: The distance between the inside seam and the edge of the cuff and the intersection between the inside seam and the bottom edge after washing.

b—Top: the distance perpendicular to the bottom edge of the intersection of the side seam and the sleeve seam;

Pants: The bottom is sewn to the inside of the hem.

 

1.4 Analysis and recommendations

The three-piece garment with the dimensional change rate of washing is directly subjected to the water-washing distortion rate test. The advantage is obvious: it saves the sample and simplifies the test, but the specification is flawed. The washing dimensional change rate index in the knitting product standard is only divided into straight and horizontal, regardless of the product type, that is, for the test of the set product, since the evaluation indexes of the top and the trousers are the same, the three test samples can be three tops. Or 3 trousers, or a total of 3 tops and trousers, the sample can be mixed side, but the mixed test can not meet the test requirements of the distortion rate after washing. This is because the distortion rate of the tops and trousers after washing is separately evaluated, and the evaluation indicators are significantly different, so the standard regulations are not applicable to the packaged products. When the standard revision is proposed, it is necessary to clarify that when the package product is tested for the distortion rate after washing, three pieces of the tops and trousers should be washed, and the average value of the distortion rate of the three samples is taken as the evaluation result.

 

The description of the meaning of the a and b values ​​in the calculation formula is also less accurate. The value of a is the displacement value before and after washing at the same point, but the point at which the side seam and the sleeve seam intersect perpendicularly to the bottom before washing is not necessarily the intersection of the side seam and the bottom edge (it is not uncommon to have distortion before washing). Therefore, the value of a specified in this standard is the distance between the point at which the side seam of the upper garment and the side of the sleeve is perpendicular to the bottom edge and the intersection between the side seam and the bottom edge after washing, including the sum of the distortion effects before and after washing. This is inconsistent with the distortion rate after washing in the assessment project, so it cannot accurately reflect the distortion effect after washing.

For the b value, it is not clearly defined whether the measurement value is taken before or after washing, and the two values ​​before and after washing are different. In addition, the length measurement unit standards of a and b are also not specified. The proposed standard accurately specifies the meaning and unit of measurement of the two values ​​a and b to ensure that the measurement method and the test results are consistent.

2. Analysis and suggestion of the evaluation index of distortion rate after washing

2.1 Twist rate assessment indicators after washing

 

Table 1 is the standard for commonly used knitting products, such as the twisting rate after washing, and other evaluation indicators (except for knitted fabrics with wool and silk as the main raw materials).

Table 1 Twisted rate evaluation index of knitted products after washing

2.2 Analysis and recommendations

 

It can be seen from the data in Table 1 that the evaluation indexes of the tops and trousers are quite different. Except for the home clothes, the evaluation indexes of the tops are doubled or doubled. This situation is among other textile evaluation items. rare. We try to analyze the reason: from Figure 1 and Figure 2, the distance between the side seam and the sleeve seam at the bottom of the bottom is about 1/2 of the distance between the bottom of the trousers and the edge of the trousers. If the value of a is The same, the twist rate F of the pants will be 1/2 of the value of the top, which is consistent with the setting of the standard indicator. Otherwise, if the F of the knitted sportswear tops and trousers is 6.0, the upper b is 40cm, if it meets the requirements of the first class, the a value is 2.4cm; the pants are measured as 80cm, if it meets one The requirements of the same product, the maximum value of a will be 4.8cm, the trousers skewed 4.8cm still meet the requirements of the first-class products, which is clearly an indicator that consumers cannot accept.

 

Therefore, the difference in the index of the distortion rate of the tops and trousers is reasonable, mainly considering the absolute value of the skew. But from another point of view, rather than assessing the distortion rate F, it is more practical than the absolute value a of the assessment skew. The current woven garment standard FZ/T81006-2007 "denim clothing" assessment of the degree of distortion is to directly measure the degree of skew, and regardless of the length of the side seam, this regulation is more intuitive and reasonable. It is recommended that the knitting standards be considered for consistency with similar assessment projects when revised.

In addition, different products with different evaluation indicators are not the same as reasonable. For example, knitted T-shirts are formal suits, and the indicators are slightly more appropriate; knitted home clothes are more casual home clothes, and the indicators are relaxed. However, knitted sportswear, knitted student uniforms and knitted casual wear are products that are not clearly classified, especially It is knitted sportswear and knit casual wear, sometimes difficult to define. From the assessment indicators in Table 1, the indicators of the superior products and the qualified products of the two types of products are exactly the same. The first-class tops are the same and the trousers are only 0.5%. Such a small difference should be said to have no practical significance. On the contrary, the assessment indicators are confusing and complicate standard operations. It is recommended that the values ​​of the distortion rate after washing, such as the knit products of similar styles, be as uniform as possible.

 

3. Conclusion

 

Through the analysis of the standard and the summary of daily work experience, this paper gives the following suggestions for the test standard of the twist rate after washing of knitted products:

 

(1) When the set product consisting of tops and trousers is measured for the twist rate after washing, the sample cannot be directly used for the three-piece garment test of the dimensional change rate of washing. It is required to add 3 pieces of washing, that is, 3 pieces of tops and 3 pieces of washing. Six pieces of trousers were counted, and the average of the distortion rates of the three samples was used as the evaluation result.

 

(2) In the actual operation, for the b value, it is recommended to take the measured value before washing, so that it can be compared with the similar method standard GB/T23319.3-2009 "Determination of the skew after textile washing - Part 3: Woven garments and Knitted garments are consistent; the length measurement units of a and b are unified in centimeters.

 

(3) When the proposed standard is revised, the distortion rate after washing in the knitted product will be revised to the degree of distortion after washing, so that the assessment project is more intuitive and reasonable, and it is guaranteed to be consistent with similar evaluation items of other clothing product standards. The evaluation index of the distortion rate after washing and other products of the knitted products makes the standard more operable.

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