Shanghai Weitao automation equipment Co., Ltd
Contact person: Mr. Lu
Address: 2312 Weiqing East Road, Shanyang Town, Jinshan District, Shanghai
Testing of air permeability of fabrics and influencing factors of air permeability
The so-called air permeability test refers to the barrier effect of packaging materials on gas and other penetrants. The air permeability test is an important index to analyze the shelf life of products from the perspective of packaging. Fabric air permeability meter is used to measure gas permeability, solubility coefficient, diffusion coefficient and permeability coefficient of plastic film, composite film, high barrier material, sheet and metal foil at various temperatures. The air permeability tester is used to test the air velocity per unit area under specific pressure conditions. Users only need to set the standard test pressure. The instrument will automatically detect the area of the test head, automatically select the size of the test hole, and automatically control the suction force of the fan.
In addition, the air permeability of fabric is an important factor affecting the comfort of fabric. Sportswear and windproof and cold proof clothes have higher requirements on the air permeability of fabrics. Some industrial textiles, such as parachute and filter cloth, have special requirements for air permeability of fabrics. The air permeability of a fabric depends on the number and size of the space between the warp and weft yarns and between the fibers, that is, it is related to the density of the warp and weft, the count of the warp and weft yarn, and the twist of the yarn. In addition, it is related to fiber properties, yarn structure, fabric thickness and volume weight.
Testing principle of fabric permeability: the so-called fabric permeability refers to the air permeability of fabric under the condition of pressure difference on both sides of the fabric. It is conventionally expressed by air permeability, that is, the air volume per unit area of the fabric vertically passing through the fabric under the specified pressure difference on both sides in unit time, and the unit is L / m2 * s. Because the pressure difference is a necessary condition for air flow, only when a certain pressure difference is maintained on both sides of the tested fabric, can air flow be generated in the fabric.
The air permeability of textiles refers to the air passing through the fabric vertically, forming a certain pressure difference on the front and back sides of the fabric. The air volume passing through the fabric in unit time under a certain pressure difference is measured. According to scientific analysis, there are many factors affecting the air permeability of the fabric, and the fabric material and fabric structure are two of them.
1. The influence of fabric material on air permeability
Five kinds of fabrics with similar texture and thickness, such as cotton, linen, wool, nylon and polyester, were selected and tested by YG (b) 461 digital air permeability tester according to GB / t5453-1997 (the same below). The results are shown in Table 2
It can be seen from table 2 that fabric material is one of the main factors affecting air permeability. In general, the air permeability of cotton, linen, wool and other natural fibers and protein fiber fabrics is better than that of nylon and polyester fabrics.
2. The influence of fabric structure on air permeability
Fabric structure is also an important factor affecting the air permeability of fabric. It can be seen from table 2 that the permeability relationship of fabrics with different weave structures is as follows: porous fabric > satin fabric > twill fabric > plain fabric. This is because plain fabric has the most times of interweaving of warp and weft threads, and the pores between yarns are smaller and the air permeability is smaller; the gap between yarns of porous fabric is larger and the air permeability is greater. Due to the change of fabric structure and density, the air permeability of fabric increases with the increase of float length. When the count of warp and weft yarn is constant, the air permeability of fabric decreases with the increase of warp and weft density, while the density of fabric remains unchanged, while the fineness of warp and weft yarn decreases, the air permeability of fabric increases. Within a certain range, yarn twist increases, yarn unit volume weight increases, yarn diameter and fabric tightness decrease, and fabric permeability increases.