The number of washes has a certain impact on the measurement of the air permeability tester

​Gas Permeability Tester Also known as differential pressure gas permeability tester. Air permeability test refers to the barrier effect of packaging materials on gases and other permeable substances. From a packaging perspective, this is an important indicator of the shelf life of the product. It is used to measure the gas permeability, solubility coefficient, diffusion coefficient and permeability coefficient of plastic films, composite films, high barrier materials, foils and metal foils at different temperatures.

Air permeability tester is used to test air flow per unit area under specific conditions and pressure. The user only needs to set the standard test pressure, and the instrument will automatically detect the test head area, automatically select the hole sizetest and will automatically control the suction force of the fan. . Suitable for a variety of fabrics, including woven fabrics, non-woven fabrics, airbag fabrics, blankets, fleece fabrics, knitted fabrics, multi-layer fabrics and cotton fleece fabrics, these fabrics can be used for competition, large surface, coated, resin treated or any other treatment. The tester can also test airflow through thick, flexible, porous objects, such as polyurethane foam.

After research, it was found that the air permeability of fabrics measured by the air permeability tester is affected by the number of washes. The durable press washing procedure was used to wash different samples, that is, the water temperature was (49 ± 3) ℃. Wash for 10 minutes, dehydrate for 4 minutes and dry it to examine the effect of washing times onthe breathability of the fabric.

Although the number of washes has different effects on the air permeability of different fabrics, they basically follow a similar rule: during the first 5 washes, the air permeability of the fabric changes significantly; after 5-100 washes, the air permeability of the fabric changes. Changes are small and tend to be stable; among them, the breathability of the fabric tends to increase slightly after more than 30 washes.

The influence of the number of washes on air permeability is directly linked to the shrinkage rate of the fabric. During fabric processing, the threads are stretched several times, causing stress concentration. When the fabric is under the action of water, the internal stress is released and the slow recovery of elastic deformation of the fibers and yarns causes a change in the size, density and tightness of the fabric, resulting in a reductionof the air permeability of the fabric. Generally, fabric shrinkage evolves significantly over the course of 5 washes, then tends to stabilize, breathability will therefore reach a turning point after 5 washes. As the number of washes increases, the fibers gradually wear out, the fabric becomes looser, the gaps between the threads increase, and the air permeability gradually increases.

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