Analysis on Factors of Influencing Moisture Permeability Test

At present, people not only demand beautiful and fashionable textile fabrics, but also more and more functional requirements, such as thermal comfort, wind resistance, air permeability, moisture permeability and water resistance, warmth retention, etc. Among them, an important index to measure the comfort of clothing is the moisture permeability of fabrics, that is, the ability of fabrics to transfer water vapor naturally discharged from the body to the external environment, which is measured according to the amount of water vapor passing through fabric samples. Today, Shanghai Pinkui will introduce the influencing factors of moisture permeability test.
Moisture permeability test refers to the moisture permeability of fabric under different ambient temperatures, which is equivalent to simulating the sweating state of human body under different activities. The 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 human body under static or little movement, and the amount of sweat discharged by human body is generally less. The test of inverted cup method simulates the moisture permeability of human body under strenuous exercise. The amount of sweat increases rapidly, and the fabric is in direct contact with sweat on human skin.

Test method of moisture permeability:
1. Equipment and reagents used
Fabric moisture permeability tester (with circulating airflow speed: 0.3-0.5m/s), desiccant (drying for 3 hours before use), distilled water.
2. Test principle:
The principle of moisture permeability test is to use a moisture permeable cup with desiccant or distilled water and seal it with a fabric sample, place the moisture permeable cup assembly in a specified temperature and humidity sealed environment, and calculate the moisture permeability according to the weight change of the moisture permeable cup assembly within a certain time.
The difference between moisture absorption method and evaporation method lies in the opposite humidity and the relative humidity in the moisture permeable cup: 0% for moisture absorption method and 100% for evaporation method. The relative humidity of the moisture permeable instrument is the set humidity of the sample. Different test methods have different results. According to the requirements, choose the test method that can truly reflect the actual moisture permeability of fabrics.

Analysis on influencing factors of moisture permeability test;
1. the influence of wind speed on moisture permeability
The wind speed of the moisture permeable instrument directly affects the experimental data. High wind speed can increase the evaporation of water. Different kinds of fabrics have different effects on it.
2. The influence of calcium chloride on moisture permeability in moisture absorption method
Because calcium chloride has water absorption, crystal water may not be completely removed in the process of repeated use, and the moisture absorption effect will decrease, resulting in deviation. Therefore, it is recommended to dry calcium chloride at high temperature (260℃).
3. Influence of distilled water on moisture permeability in evaporation method
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, try to make the temperature of distilled water consistent with the test temperature. The higher the water temperature, the greater the evaporation of water.
4. The influence of test equilibrium time on test results in distillation method
Under the same environment, when the test time is 2 hours after balancing for 0.5 hours and 1 hour, the test results will be different due to different styles of fabrics. Therefore, it is suggested that the test balance time should be 1 hour.
5. The influence of the test surface orientation of the sample on the test
The orientation of the test fabric also has a great influence on the test results, especially in different manufacturing structures and coatings, and the influence degree varies in different situations.

Other precautions:
1. the test should be debugged in the constant temperature and humidity room for more than 4 hours
2. Calcium chloride should not be exposed directly in the air after being dried at high temperature.
3. Try to shorten the time in the weighing process after taking out the sample in the desiccant method.