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Test method for waterproof, hydrostatic pressure, vapour and air permeability of textiles

May 12, 2021

Test method for waterproof, hydrostatic pressure, vapour and air permeability of textiles



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Textile production and fabrication are complex. The clothes that people wear actually go through numerous processes before they change from cotton or yarn to fabric products, including textile clothing test categories up to hundreds of kinds, such as shrinkage, fade, water permeability, heat preservation.....Here, will briefly explain the performance test methods of waterproof, hydrostatic pressure, vapour and air permeability of textiles.



.Hydrostatic pressure


It used to call resistance to water pressure in outdoor fabric industry , unit with mmH2O, refers to the strength of water pressure per unit area. Under standard laboratory conditions, the fabric is subjected to the pressure of the upward spray of distilled water, and the maximum water pressure is recorded, such as the water pressure of 5000mmH2O, that is, the maximum pressure per unit area can withstand 5m without leakage.


Common test standard: AATCC 127; JIS L1092B; EN: IS0 811;
WaterProofness is divided into two methods: before washing and after washing


1.Test before washing: domestic outdoor brands generally test the water pressure resistance value before washing, not test the water pressure resistance value after washing. After washing several times, the water pressure resistance value drops greatly, which may decrease by about 1000-3000mmH2O.


2.Test after washing: some famous outdoor brands abroad, they generally test WaterProofness after 5 times washing, THENORTHFACE even test water pressure resistance after 20 times washing. Because of many times after washing test, the drop in water pressure value is large. Such a test method means that any coating plant or laminating plant must be processed with better materials, For example, the water pressure resistance of coated fabrics is required to reach 5000mmH2O after 5 times of washing, so it should be at least 7-8000mmH2O before washing; Of course, such a requirement would lead to higher prices.



.Air Permeabbility


Means the ability of air to pass through the fabric; Under the condition of specified pressure difference, the airflow that passes through a given area of the sample in a certain time is measured, and the air permeability is calculated. The airflow rate can be measured directly or can be converted by measuring the pressure on both sides of the flow aperture. This is really breathable.


Test standards: ASTM D737, ISO 9237, JIS L1096

Air permeablity units: mm/s, cm3/cm2/s





In the standard laboratory, the sample is sprayed with distilled water through a funnel and graded against the standard waterproof sample.


Common test standard: AATCC 22, ISO 4920


1.Three kinds for WaterRepellent: WaterRepellent (WR); DurableWaterRepellent (DWR), used to be called super splashing water in outdoor fabric industry; TEFLON

W/R: If you often go hiking or a mountain with a certain altitude, the weather on the mountain is changeable and it may rain at any time. If you wash the ordinary waterproof clothes for several times without waterproof, the surface of the clothes will get wet, it will increase the body bearing when wear.


2.DWR: Japan Daikin carbon 6 waterproof, wash 20 times to maintain 80 points effect (European standard level 3); Carbon 8 used to be waterproof and could reach 80 points after 30 washes, but it has been banned by the European Union because its fluoride content does not meet the EU standard.


3.TEFLON: DuPont production in the United States, very high visibility, waterproof, anti-fouling, oil and other three prevention effect, the price is more expensive, buy this brand of waterproof can provide Teflon tag, but the shortcomings of Teflon anti-splash effect is not as good as carbon 8, carbon 6.



Ⅳ.Water vapour permeability (Shorthand for MP)


The water vapour permeability is expressed in unit g/m2/24h, which means that under certain standard laboratory conditions, a specific humidity difference is formed on both sides of the sample, and the water vapor enters the dry side through the sample. By measuring the change of the weight of the vapour permeability cup with time, the water vapor transmission rate and other parameters of the sample can be obtained.

There are two test methods for water vapour permeability: Straight and poured

Straight way: ASTM E96 A、C、E; JIS L1099 A1

Poured way: ASTM-E96, JIS L1099B1

This test uses pre-wash data.


Domestic outdoor practitioners and outdoor enthusiasts all call water vapor permeability , or directly air perrmeability. It is incorrect and not rigorous to confuse the two words together. Air perrmeability and water vapor permeability are completely two concepts, which need to be differentiated and correctly understood.

The above three functional indicators of the fabric is called waterproof and moisture-permeable fabric, also known as windproof, waterproof, warm and moisture-permeable fabric, simple understanding is that the rain outside can not come, the sweat inside through the pores of the coating and film out.