Textile materials include textile raw materials and textile semi-finished products processed into textiles, such as Various fibers, slivers, yarns, fabrics, etc. The hygroscopicity of textile materials is an important characteristic related to material performance and processing technology. The hygroscopicity of textile materials is usually expressed by the moisture regain rate and the official moisture regain rate of textile materials. These basic quality indicators play a very important role in the commercial trade, performance testing and textile processing of textile materials. Common moisture regain test methods for textile materials Test methods (1) direct measurement method (2) indirect measurement method.
Moisture regain and official moisture regain: The moisture regain of textile materials is the percentage of the amount of water adsorbed in the sample to the dry weight of the sample. The moisture regain of textile materials varies from time to time, as does their weight. In order to eliminate weight differences caused by different moisture regains and meet the needs of textile material trade and inspection, the country has stipulated corresponding standards for the moisture regain of various textile materials, called the official moisture regain, which is numerically close to the standard temperature and humidity Equilibrium moisture regain measured under conditions. It should be noted that the regulations on the official moisture regain rate of textile materials in various countries are often based on their own actual conditions, so they are not completely consistent.
There are many methods for testing the moisture regain of textile materials:
(1) Direct measurement Method: First weigh the sample, then remove the moisture, then weigh the dry weight of the sample to calculate the actual moisture regain. Depending on the method of removing moisture, direct measurement methods include: oven method, infrared radiation method, high-frequency electric field heating method, vacuum drying method and hygroscopic agent drying method. The oven method and infrared radiation method are often used in industrial production. The advantage of the oven method is that the measurement results are more accurate, but the disadvantage is that it is slow and has low efficiency. The advantages of the infrared radiation method are fast speed, high efficiency, and energy saving. The disadvantages are that the temperature is difficult to control and the measurement results fluctuate.
(2) Indirect determination method: It uses the relationship between certain properties of the fiber and the moisture regain to indirectly estimate the moisture regain of the fiber. The advantages of this method are fast speed and high efficiency, but the determination of the relationship between fiber-related properties and moisture regain still requires the use of a direct method. Indirect methods can be divided into resistance method, capacitance method, infrared absorption method and microwave method. In China, the resistance method is often used to measure the moisture content of raw cotton. The microwave method has the characteristics of rapid, continuous, non-contact and non-destructive. It can be used for continuous measurement and automatic control. It is a new technology that is still developing recently.
Introduction to the commonly used oven method: It uses resistance heating in the oven to bring the temperature of the air in the oven to a certain value, and maintains this temperature throughout the drying, and then weighs the wet weight of the textile. The material sample is placed in a constant temperature oven for drying to make the textile The moisture in the material continues to evaporate in the hot air, and the exhaust device of the oven is used to continuously discharge the hot and humid air out of the box, creating conditions for the moisture contained in the textile material to continuously evaporate and lose. When the weight is dried until it remains unchanged, it is the dry weight of the textile material. At this time, the dry weight of the sample can be obtained by using the method of thermal weighing in the box, and then the textile weight can be obtained based on the wet weight and dry weight of the sample. The resurgence of materials In the oven method, the drying temperature is 105℃±3℃; for wool and most chemical fibers, it is 105~220℃; the drying time for silk is generally 90min.
In addition, the moisture regain of textile materials can also be measured by the resistance wet method. The resistance wet method is based on the different resistivities of textile materials at different moisture regains, thereby measuring the moisture contained in textile materials. For dry moisture Commodities with unstable rates, such as wool, raw silk, cotton, etc., in order to accurately calculate the weight of such commodities, metric (Conditioned) is usually used internationally. Weight) calculation method, that is, measuring the actual moisture regain (moisture content) of the product to calculate the clean weight of the product, and then converting it into the weight of the official moisture regain.
Calculation. The formula is as follows: common quantity = [actual weight of product/(1 + actual moisture regain)] ╳ (1 + official moisture regain rate) = clean weight of the product ╳ (1 + official moisture regain rate)
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