Knitted T-shirts Inspection Requirements and Methods

Knitted T-shirts are lightweight, comfortable, and form-fitting tops made of knitted fabric. They are widely used for everyday wear, leisure activities, and corporate and group customization. Knitted fabrics are made of woven yarn coils and offer excellent elasticity, breathability, and softness, allowing the T-shirt to fit the body more closely and allow for greater freedom of movement. They are popular with men, women, and children alike.

Common fabrics include pure cotton, cotton-spandex blends, polyester-cotton, and modal. These fabrics are not only soft and moisture-wicking, but also washable and durable. Knitted T-shirts come in a variety of styles, including crew necks, V-necks, and lapels, in a variety of colors and can be printed, embroidered, or printed, offering both practicality and fashion.

As one of the most basic and versatile clothing items, knitted T-shirts not only reflect the wearer's comfort needs, but also become an important carrier for expressing personality and brand culture. They are an indispensable classic item in modern clothing consumption.

Require

Grading regulations

The quality grades are divided into superior products, first-class products and qualified products.

The intrinsic quality is graded by criticism, and the appearance quality is graded by piece, and the combination of the two is used to determine the lowest grade.

The lowest test result of each intrinsic quality index will be used as the basis for evaluating the batch of products.

When the same product has appearance quality problems belonging to different grades, it shall be evaluated according to the lowest grade. Only two surface defects of the same grade can exist on the same product. If more than two surface defects are found, the product shall be downgraded by one grade.

Intrinsic quality requirements

Intrinsic quality requirements shall comply with regulations.

Color classification is carried out according to the provisions of GSB16-2159. Colors with a depth greater than 1/12 of the standard are considered dark colors, and colors with a depth not greater than 1/12 of the standard are considered light colors.

Children's knitted T-shirts should also comply with the relevant requirements of GB31701.

Appearance quality requirements

Surface defect evaluation regulations

Surface defects shall be rated according to regulations.

Description of defect level: Minor - not obvious visually, can only be seen through careful identification.

Defects not listed in the table shall be handled in accordance with the provisions of surface defect evaluation and grading in GB/T8878. Other surface defects not specified shall be handled in accordance with similar defects.

The degree of surface defects shall be in accordance with the provisions of GSB16-2500.

Specification size deviation

Specification size deviations should comply with regulations.

Symmetrical size differences

The size difference of symmetrical parts should comply with regulations.

Sewing regulations

The shoulders, collars, and seam starts and ends should be reinforced.

The sewing should be firm and smooth, and the seams should be straight, smooth, and of appropriate tightness.

The stitching should be smooth, the collar should be straight, symmetrical and not warped, the placket should be flat and straight, the sleeves and bottom hem should be of the same width, ironed flat, the seams should be ironed out, the threads should be trimmed and there should be no debris.

The buttonholes should be neat and the buttons should be secure.

Chain sewing should not cause stitch skipping or thread breakage.

test

Internal quality inspection

Preparation and test conditions

The specimens taken should not have defects that may affect the test.

Before testing the dimensional change rate after washing and the distortion rate after washing, the humidity should be adjusted according to the standard atmosphere specified in GB/T6529, and the test can be carried out only after the humidity adjustment meets the requirements.

Test methods

The fiber content shall comply with the provisions of FZ/T01057 (all parts), GB/T2910 (all parts), GB/T38015, FZ/T01026, FZ/T01101, etc.

The formaldehyde content shall be in accordance with the provisions of GB/T2912.1.

The pH value shall be in accordance with the provisions of GB/T7573.

Odor shall be handled in accordance with the provisions of GB18401.

Decomposable carcinogenic aromatic amine dyes shall be implemented in accordance with the provisions of GB/T17592.

The bursting strength shall be in accordance with the provisions of GB/T19976-2005, and the diameter of the steel ball shall be (38±0.02) mm.

The calculation basis for the washing size change rate measurement part is the average value of the vertical length of the garment at the front, back, left and right sides, and the horizontal measurement value of the front body is used as the calculation basis. Marks are made separately during measurement for easy measurement after washing.

The washing procedure was carried out according to the 4N program for Type A washing machines in Appendix A of GB/T8629-2017. Products marked "Hand wash only" were washed according to the 4H program for Type A washing machines in Appendix A of GB/T8629-2017. Products containing 30% or more of gross material were washed according to the 4G program for Type A washing machines in Appendix A of GB/T8629-2017. "Standard Detergent 3" was used as the detergent. Three items were tested, and the number of washes was one.

Hang the sample to dry according to the drying procedure specified in 10.1.1 Procedure A of GB/T 8629-2017. Pass a rod through both sleeves, ensuring the bust and shoulder area are straight. Manually separate the front and back of the sample from the bottom and straighten them. After drying, place the sample on a platform at a temperature of (20 ± 2)°C and a relative humidity of (65 ± 4)%. After 4 hours, gently pat any creases to smooth them out before measuring.

Calculate the dimensional change rate after washing in the longitudinal and transverse directions according to formula (1). A negative sign (-) indicates dimensional shrinkage, and a positive sign (+) indicates dimensional elongation (inverse expansion). The arithmetic mean of the three specimens is used as the test result. If both shrinkage and inverse expansion test results are present, the arithmetic mean of the two shrinkage or elongation specimens is used as the test result. The final result is rounded according to the provisions of GB/T8170 to one decimal place.

A=(L₁-L₀)/L₀×100%

Where:
A——vertical or transverse washing dimensional change rate;
L₁ – the average of the dimensions after washing in the longitudinal or transverse direction, in centimeters (cm);
L₀ is the average length of the fabric before washing, measured in centimeters (cm).

The dry cleaning dimensional change rate is carried out in accordance with the provisions of 8.1 Conventional Dry Cleaning Method in FZ/T80007.3-2006, with one test piece. The measurement is carried out according to the water washing dimensional change rate test method.

Post-wash distortion is measured by laying the washed garment on a smooth surface and gently flattening it with your hands. Measurements are taken on the side of each garment with the greatest distortion. The distortion is measured at the point where the hem and armhole seam intersect, perpendicular to the bottom edge, and the intersection of the hem and bottom edge (in centimeters). All data is calculated after washing. Any distortion present before washing should be noted and reported.

Calculation of the distortion rate after washing The calculation method of formula (2) was used. The average value of the distortion rate of three garments after washing was used as the calculation result. The final result was rounded off according to the provisions of GB/T8170 and retained one decimal place.

F=a/b×100%

Where:
F——distortion rate;
a, b——See Figure 2.

The color fastness to soap washing shall be carried out in accordance with the provisions of Table 2 Test Method A (1) in GB/T3921-2008.

The color fastness to water shall be in accordance with the provisions of GB/T5713.

Color fastness to perspiration shall be in accordance with the provisions of GB/T3922.

The color fastness to rubbing shall be carried out in accordance with the provisions of GB/T3920 and only tested in the vertical direction.

The color fastness to light shall be determined in accordance with the provisions of 8.3.4 Method 3 in GB/T8427-2019. When the rating difference between each stage exceeds half a grade, the average color fastness to light shall be used for judgment.

The color fastness to dry cleaning shall be in accordance with the provisions of GB/T5711.

The color fastness test for splicing shall be conducted in accordance with the provisions of 7.1 Method A in GB/T31127-2014. For fabrics or products with added edge (strip) whose specimen dimensions do not meet the requirement of (100±2)mm×(40±2)mm, the specimen may be cut to the maximum size of the actual specimen and then two specimens may be sewn together along the short edges to form a combined specimen.

The combined color fastness to light and perspiration shall be in accordance with the provisions of GB/T14576.

The degree of staining of the washing liquid is determined by preparing and washing the sample according to the conditions of Method A (1) in Table 2 of GB/T3921-2008. The sample is then filtered with qualitative filter paper (medium speed) to remove impurities from the residual soap solution. The filtered soap solution is poured into a colorimetric tube with a diameter of 25 mm. The unwashed soap solution at the same temperature as the test temperature is poured into another colorimetric tube (diameter 25 mm) as a reference sample. Under D65 standard light source, with white cardboard without fluorescent whitening agent as the background, the cardboard is placed on a rating rack, and the degree of staining of the washing liquid is evaluated according to the requirements of GB/T251. The amount of soap solution poured into the colorimetric tube is about 50 mL. The distance between the colorimetric tube and the white cardboard during the rating is about 10 cm to avoid interference from the colorimetric tube's shadow. The rating should be completed within 15 minutes.

Pilling is carried out in accordance with the provisions of parameter E in Table 1 of GB/T4802.1-2008, and the rating is assessed according to the requirements of GSB16-1523 based on the fabric style and pilling shape.

Products containing 30% or more wool are evaluated according to GB/T 4802.3. Combed fabrics are tumbled at 14,400 r/min, while semi-combed and carded fabrics are tumbled at 7,200 r/min. Rating is based on fabric style and pilling pattern. Combed fabrics are evaluated according to GSB 16-2923, while semi-combed and carded fabrics are evaluated according to GSB 16-2922.

The appearance quality after washing and dry cleaning shall be washed and dried in accordance with the test methods for dimensional change rate after washing in 6.1.2.7 and dimensional change rate after dry cleaning in 6.1.2.8, and the washed garments shall be evaluated piece by piece in accordance with the requirements of Table 1.

Appearance quality inspection

Appearance quality inspection conditions

Generally, light inspection is adopted, and the inspection should be carried out under a light source with an illumination of not less than 600lx. If natural light source is used indoors, natural northern light should be used as the standard.

During inspection, the product should be spread flat on the inspection table with a layer of white cloth on it. The inspector should look directly at the surface of the spread product, with the distance between the eyes and the product at least 35 cm.

Measurement location and method

Measure each part with an accuracy of 0.1cm.

The grain skewness shall be in accordance with the provisions of GB/T14801.

Color difference shall be implemented in accordance with the provisions of GB/T250.

Decision rules

Batch determination

Intrinsic quality

If one or more items of intrinsic quality do not meet the requirements of 5.2, the batch of products will be deemed unqualified. Among them, if the color fastness item does not meet the requirements, the batch of products will be deemed unqualified according to the color.

If at least two pieces of the appearance quality inspection results after washing are qualified, the batch of products is assessed as qualified; otherwise, the batch of products is judged as unqualified.

Appearance quality

The non-conforming product rate for appearance quality is calculated by type and color. If the non-conforming product rate is 5% or less, the batch of products is considered qualified; if the non-conforming product rate is above 5%, the batch of products is considered unqualified.

Result determination

If both 8.1.1 and 8.1.2 are passed, the batch of products is considered qualified.

Single piece determination

If the number of product inspection pieces is lower than the number of sampling pieces for batch determination, the internal quality and appearance quality shall be determined only on the inspected products in accordance with 8.1, and this shall be noted in the inspection report.

other

There should be no defects that seriously affect the performance.