There are many varieties of knitted products in China, and different varieties have different characteristics. The industry standard of knitted thermal underwear batting class has made standardized requirements for thermal insulation underwear of battings.
The batting layer is made by a needle-punching carding process using melt-blown methods, including wool, silk, and non-woven batting layers of various chemical fibers.
Insulation rate Air permeability Moisture permeability rate According to the characteristics of "Knitted thermal underwear", "Insulation knitted thermal underwear category" industry standards stipulate 11 internal quality indicators, insulation rate, square meters of dry weight, air permeability, moisture permeability , Pilling, the strength of the top of the marble, the dimensional change rate of the washing, the stretching elasticity, the formaldehyde content, the fiber content, and the color fastness. Among them, the insulation rate, air permeability, and moisture permeability are important indexes reflecting the comfort of thermal underwear. At present, the knitted thermal underwear with knitted layer occupies a large proportion in the market. The structure of the product is a warm layer formed by the composite of flakes in the middle layer, which is the fastest-changing type of development at present. The intermediate batt may use synthetic fiber composite fibers, polyester polypropylene staple fibers, functional fibers, silk, and wool. The structure of the fabric generally adopts a knitted single-sided structure, and the fiber raw materials generally use cotton, polyester-cotton blended fiber, modified polypropylene fiber, and the like. According to experts' arguments, a comfortable undergarment is the result of the best fit of the three indicators, namely, the heat preservation rate is over 50%, the air permeability is controlled between 300 and 600 mm/s, and the moisture permeability is greater than 3000 g/m 2 /day. .
Pilling In addition, in order to ensure the wearing performance of knitted thermal underwear, the standard also specifies the specifications for pilling, dimensional change rate of water washing, stretch elasticity, formaldehyde content, and dyeing rate. Among them, pilling, dimensional change rate of washing, and color fastness are directly felt by the consumer after wearing. For example, if the pilling index is evaluated after the product has been rubbed, the fiber end protrudes from the surface to form a pile or a small ball-like protrusion. The quality of this indicator is related to the cotton used. The use of low-cotton or polyester-cotton woven products is easy to pilling, and pure cotton products are not easy to pill.
Water Wash Size Change The rate of change in water wash size specifies the method of measuring the change in size of a textile after it has been treated with an appropriate washing and drying combination program. The test washing temperature is 40 °C, to remind consumers to grasp the temperature in the process of washing warm underwear, it is best to wash at 40 °C water temperature, otherwise it will cause poor washing results.
The color fastness test of color fastness is a comprehensive evaluation of the degree of discoloration of textiles from the three aspects of acid resistance, alkali resistance and friction resistance. The color fastness is low and the product is heavily discolored.
Formaldehyde content The formaldehyde content also makes stringent requirements regarding formaldehyde content. According to the analysis, formaldehyde is generally present in some finishing agents, and some knit thermal underwears use adhesives during processing, which is one of the factors that lead to the presence of formaldehyde. After a large number of tests, we finally determined the formaldehyde content as ≤50mg/kg.
Invited Expert: Xing Zhigui, Deputy Director of National Knitwear Quality Supervision and Inspection Center
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