Textile Testing Instruments - Analysis of Influencing Factors of Moisture Permeability Test

At present, besides the requirement of beautiful and fashionable textile fabrics, there are more and more functional requirements, such as thermal comfort, wind resistance, air permeability, moisture permeability, waterproofness, warmth, etc., in which the comfort of the garment is measured. An important indicator of sex is the moisture permeability of the fabric, which is the ability of the fabric to transfer the body's natural water vapor to the external environment. She measures the amount of water vapor that passes through the fabric sample. Today, Shanghai Quebec will introduce the factors that influence the moisture permeability test.

The moisture permeability test refers to the moisture permeability of the fabric at different ambient temperatures, which is equivalent to simulating the sweating state of the human body under different active conditions. Moisture permeability is divided into: positive cup method and inverted cup method. The positive cup method simulates the moisture permeability of the fabric worn by the human body in a resting state or in a small amount of exercise. Generally, the body discharges less sweat. The inverted cup test simulates the human body's moisture permeability during vigorous exercise. The amount of human sweat increases dramatically and the fabric is in direct contact with the sweat on the human skin.

Moisture permeability test method:

1. Equipment and reagents used

Fabric moisture permeability tester (with circulating air velocity: 0.3-0.5m/s in size), desiccant (dry 3 hours before use), distilled water.

2. Test principle:

The principle of moisture permeability test is to use a moisture-permeable cup made with desiccant or distilled water and sealed with a fabric sample. Place the moisture-permeable cup assembly in the specified temperature and humidity sealed environment, according to the weight of the moisture-permeable cup assembly within a certain period of time. The change calculates the moisture permeability.

The difference between the moisture absorption method and the evaporation method is the humidity of the opposite surface and the relative humidity in the moisture-permeable cup: the moisture absorption method is 0%, and the evaporation method is 100%. The relative humidity of the moisture permeable instrument sets the humidity for the sample. The results obtained by different test methods are also different. According to the requirements, a test method that can truly reflect the actual moisture permeability of the fabric is selected.

Analysis of factors affecting moisture permeability testing:

1. Effect of wind speed on moisture permeability

The wind speed of the moisture permeability meter directly affects the experimental data, and the wind speed can increase the evaporation of water. Different types of fabrics have different degrees of influence on the wind speed.

2. Effect of calcium chloride on hygroscopicity in hygroscopic method

Due to the water absorption of calcium chloride, the crystal water may not be completely removed during repeated use, the moisture absorption effect will be reduced, and the results will be biased. Therefore, it is recommended that calcium chloride be dried at a high temperature (260 degrees).

3. Effect of distilled water on moisture permeability in evaporation

We know that there are two temperatures to choose from in the test requirements, one is 23 degrees Celsius and the other is 38 degrees Celsius. Before the test, the temperature of the distilled water is the same as the test temperature. The water temperature is high and the evaporation of water is large.

4. Effect of test equilibrium time on test results in distillation

Under the same circumstances, the test results will vary according to the style of different fabrics when the test balance is 0.5 hours and 1 hour, and the test time is 2 hours. Therefore, it is recommended that the test balance time should be 1 hour.

5. Influence of the test surface of the sample on the test

The test fabric orientation also has a great influence on the test results, especially the manufacturing structure is different, there are coatings, etc., and the degree of influence varies.

Other notes:

1 test should be in the constant temperature and humidity chamber debugging more than 4 hours

2. Calcium chloride should be avoided from exposure to air directly after drying at high temperatures.

3. Take the sample out of the desiccant method and try to shorten the time during the weighing process.