1. What is fabric shrinkage?

Shrinkage rate of fabric refers to the percentage of fabric shrinkage after washing or soaking. Synthetic fibers and blended fabrics have the smallest shrinkage, followed by wool, hemp and cotton fabrics, and silk fabrics have the largest shrinkage, while viscose, rayon and rayon fabrics have the largest shrinkage.

The shrinkage rate of fabrics can generally be divided into: 1. Natural shrinkage refers to the natural shrinkage of fabrics after ironing or relaxation in bulk production; 2. Shrinkage after washing refers to the shrinkage of ready-made clothes after washing.

The method to test the correct shrinkage of the fabric should be the same as the washing type of the large ready-to-wear clothes. If the ready-to-wear clothes do not wash, the fabric should be measured after being pumped with a steam iron.

Note: The shrinkage of general fabrics is:

Cotton 4% - 10%; Chemical fiber 4% - 8%; Cotton polyester 3.5% - 5.5%; 3% for plain white cloth; 3-4% for woolen blue cloth; Poplin is 3-4. 5%; 3 - 3.5% for calico; The value of Cartier gabardine is 4-5.5; 4% for twill cloth; Creak is 3-4%; Labor cloth is 10%; 10% for rayon.

2. What are the factors affecting shrinkage?

① The shrinkage rate of fabrics is different with different raw materials. Generally speaking, the fibers with high hygroscopicity will expand, increase in diameter, shorten in length and increase in shrinkage after immersion. For example, the water absorption of some viscose fibers is as high as 13%, while the water absorption of synthetic fiber fabrics is poor, and its shrinkage is small.

② The shrinkage of the fabric varies with its density. If the density in longitude and latitude is similar, the shrinkage in longitude and latitude is also close. The warp shrinkage of fabrics with high warp density will be large. On the contrary, the weft shrinkage of fabrics with higher weft density will be large.

③ The shrinkage rate of the fabric varies with the yarn count. The shrinkage rate of coarse count fabric is large, and that of fine count fabric is small.

④ The shrinkage of fabrics varies with the production process. Generally speaking, in the process of weaving, dyeing and finishing, the fiber needs to be stretched many times, and the processing time is long. The shrinkage of the fabric with large tension is large, and vice versa.

After clarifying the above problems, let's introduce the test method of shrinkage. 1. Reference standards:

GB/T8629-2001, FZ/T70009, ISO5077/6330, IWS TM31, BS 4923, EN25077/26330, JIS L1909, etc

2. Reference test tools:

① Shrinkage tester

② Dryer

③ Shrinkage rate washable cloth

④ Standard detergent

⑤ Shrinkage marking plate

⑥ Steel ruler

⑦ Others (sewing machine, textile butter pen, etc.)

3. Test steps (taking the national standard as an example):

① Take 50 from the middle of the sample with the shrinkage marking plate × 50cm size sample and mark with a textile butter pen 35 × 35cm, and sew the edge of the sample.

② Put it into the shrinkage washing machine with the washcloth, and pour in the standard detergent. ③ After washing, use a dryer to dry or dry naturally.

④ Use a steel ruler to measure the size after washing and drying.

⑤ Shrinkage rate=(size before washing - size after washing)/size before washing × 100% Generally, the radial and weft shrinkage of the fabric should be measured.