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Interpretation of waterproof, windproof and breathable functional fabrics

Feb 06/2021 / news / Author: DongJing

Summer is a rainy season. For those who love the outdoors, there are good and bad. When you go hiking, you may encounter rain. If you continue to climb with an umbrella, it will inevitably be a lot of inconvenience. Mountain climbing is a very physical exercise and will emit a lot of sweat, but the low temperature on the mountain does not allow you to take off your clothes. How to solve this kind of problem? In fact, people began to study this problem very early, that is, wearing a waterproof and breathable clothing (usually professionals often call it breathable fabric, this kind of breathability is not the gas in the air. It's the steam that evaporates from sweat). Waterproof and breathable fabric means that water cannot penetrate into the fabric under a certain pressure, and the sweat emitted by the human body can be transmitted to the outside through the fabric in the form of water vapor, so as to prevent sweat from accumulating and condensing between the body surface and the fabric to keep the clothes worn. Comfortability, it is a high-tech, unique functional fabric. Waterproofing is not a problem for the fabric industry.
1. Realize ventilation by laminating waterproof and breathable membrane
(1) PTFE film 
The diameter of water vapor molecules is 0.0004 microns, the diameter of the smallest mist in rainwater is 20 microns, and the diameter of drizzle is as high as 400 microns. If a film with a pore diameter between water vapor and rainwater can be made, it can be both waterproof and Breathable. U.S. Gore Company used polytetrafluoroethylene (PTFE) to become the first company to produce the film, and after laminating it with fabric, it was named as GORE-TEX film. After continuous efforts, it becomes a composite film by laminating with other hydrophilic films. Special treatment on the film greatly improves its fastness. It is generally believed that the water pressure of the fabric can reach 10000mm, and the water pressure will decrease significantly after washing 6-7 times; the maximum air permeability can reach 10000g/sqm*24hrs, but it is not possible that the fabric just made can reach this value. After several washings, part of the glue is washed away, the available pores increase, and the air permeability increases; at the same time, the clothing made of this fabric can also block the intrusion of cold wind, preventing the wind from taking away the heat emitted by the body through the cloth, making the body not It feels cold due to the loss of heat; in addition, the fabric can resist 97.5% of ultraviolet rays.
(2) TPU film

TPU is short for Thermoplastic Polyurethane Film, which is a non-porous hydrophilic film. Since the film itself has no pores, the waterproof effect is naturally good. Ventilation is mainly achieved through its hydrophilic properties. Relying on the difference in vapor pressure inside and outside the clothes, the steam is transferred from high pressure to low pressure, thus realizing the function of ventilation.
2. Realize breathability through coating
Using process technologies such as dry direct coating, transfer coating, foam coating, phase inversion or wet coating (solidified coating), various coating agents with waterproof and breathable functions are applied to the fabric. On the surface, the pores on the surface of the fabric are closed or reduced to a certain extent by the coating agent to obtain water resistance. The air permeability of the fabric is through the microporous structure formed on the coating by a special method or the hydrophilic group in the coating agent interacts with water molecules. With the help of hydrogen bonds and other intermolecular forces, the water molecules are adsorbed on the high humidity side. It can be obtained by transferring to the analysis function of the low temperature side. Coated fabrics are widely used because of their low price and certain air permeability. However, due to its poor waterproof and breathable performance and unsatisfactory feel, the market share is gradually decreasing.   The wet transfer coating fabric developed now makes the coated fabric look new. It not only has high physical properties such as waterproof and breathable, but also can be treated with 100% Teflon, and the washing fastness can reach more than 25 times, and the hand feel is very good.

3. Through fiber to achieve ventilation

(1) Ventair fabric.

It was designed by the British Shirley Research Institute in the 1940s. It used Egyptian long-staple cotton high-count, low-twist pure cotton yarn and high-density heavy-weight flat fabric. It was originally mainly used for cold-proof and anti-cold resistance of British Air Force pilots during World War II. Immersion. When the fabric is dry, the gap between the warp and weft yarns is relatively large, about 10 microns, which can provide a highly breathable structure; when the fabric is exposed to rain or water, the cotton yarn expands, reducing the gap between the yarns to 3 to 4 microns. A closed cell mechanism is combined with a special water-repellent finishing to ensure that the fabric is not further penetrated by rain. This type of fabric has long been replaced by other waterproof and breathable fabrics.

(2) Coolmax fabrics

Perspiration can be discharged from the body by creating holes in the fiber, which is the moisture wicking fabric currently on the market.