Introduction of textile water permeability and water resistance testing

With the continuous improvement of people's quality of life and the continuous progress of the textile industry, some basic functions of traditional textiles can no longer meet people's needs. Various functional textiles have received widespread attention, and the requirements for textile performance are getting higher and higher.

 

What is textile waterproof and water permeability?

 

People often come into contact with water in daily life, which puts forward waterproof requirements for various textiles. The waterproofness and permeability of textiles are two aspects of the same performance of textiles, namely the water resistance of textiles and the water permeability of textiles.

Textile waterproof test category

 

The main indicators of textile waterproofing are water immersion grade, hydrostatic pressure resistance grade and water vapor permeability tester. There are two test methods: spray method and hydrostatic pressure method. In order to measure the water permeability or water resistance of the fabric, different methods are used according to the actual use of the fabric, and the corresponding index is used to indicate the water permeability of the fabric.

 

1. Spray method

 

The spray method evaluates the waterproofness of fabrics by comparing standard samples with different wettability levels with water stain characteristics (continuous spraying on the samples for a fixed time). The spray method simulates the degree to which the sweater becomes wet in a drizzle.

 

In the AATCC22 test method, an iron ring with a diameter of 152.4 mm is used to fix the sample, and the surface of the sample is flat without wrinkles. Spray distilled water (250mL) on the sample 150mm under the nozzle for 25-30s, then compare the surface of the sprayed sample with the standard chart card and make a rating. The test uses a spray tester.

 

2. Water pressure method

 

Hydrostatic pressure refers to the permeability test equipment of textiles under a certain water pressure. Suitable for all kinds of fabrics, including water-repellent treated fabrics. The fabric waterproof adopts static pressure method, including static pressure method and dynamic pressure method. Static pressure is used for water-conducting fabrics, and dynamic pressure is used for coated fabrics or dense fabrics.

 

In the AATCC127 test method, cut at least three samples with an area of ​​200mm*200mm along the diagonal of the tested sample. The water resistance of the two sides of the sample is different and should be marked. Use distilled water to test at (21±2)°C with a test area of ​​100cm2. The water pressure increases at a constant speed. If there are 3 water droplets at different positions on the sample, the test will be completed (however, if the water droplets seep within 3 mm of the sample clamp, the test will be invalid). The result is the average of three samples under the same conditions. The greater the test value, the greater the pressure required for water seepage, and the better its waterproof performance. The test uses a hydraulic testing machine.

 

3. Rain test method

 

The rain test method is to simulate the waterproof performance of the fabric exposed to the air during heavy rain. This method is suitable for any fabric with water-repellent treatment or non-water-repellent treatment. Principle: Wrap the test sample around the weighing absorbent paper, and weigh the absorbent paper again after the test. The difference between twice the weight is the water permeability of the sample.

 

In the AATCC35 test method, a standard absorbent paper, measuring 152cm×152cm, is placed on the back of the sample, and the standard absorbent paper is weighed to the nearest 0.1g. On a vertical rigid surface, clamp the sample on the sample holder, place it in the middle of the nozzle, 30.5 cm away from the nozzle, and spray a stream of water at S (27±1)°C. Level for 5 minutes, after spraying, carefully take out the absorbent paper and quickly weigh to 0.1g. Calculate the weight of the paper during the spraying process and take the average of the test data. A rainfall tester was used in the test.

Factors of affecting the breathability or waterproofness of textiles

 

The permeability testing equipment of a textile is the ability of liquid water to penetrate from one side to the other. There are three main factors that affect the waterproofness and water permeability of textiles.

 

1. Fabric coating: using waterproof, microporous coating can form a good waterproof, water-permeable, and air-permeable coated fabric, which is mainly used for cloaks or raincoats.

 

2. Fiber surface wettability: The wettability of the fiber is related to the compactness of the fiber structure when the structure is tight, and the waterproof effect is better.

3. Environment: The relative humidity of the water-conducting fabric increases, the moisture absorption of the fiber increases, and the water conductivity of the fabric increases.