What is waterproof breathable fabric? What is the principle of waterproof breathable fabric?
What is waterproof breathable fabric? What is the principle of waterproof breathable fabric? What are the functions and uses of waterproof breathable fabric? Test methods for waterproof breathable functional fabric
Waterproof fabrics and breathable fabrics sound like a pair of contradictions. Since the fabric is waterproof, it is sealed. We all know that water is pervasive, so how can it be breathable? In fact, this is related to the characteristics of water. As we all know, the surface of water has tension. In life, we can find that when we pour water, the water can often be a little higher than the mouth of the cup without flowing out. This is the surface tension of water. As a result, this phenomenon is mainly because water molecules only have a relatively large molecular attraction, making each water molecule as closely connected as possible without being separated. Water vapor is also a water molecule, but at this time, the distance between each water molecule are completely independent and therefore not so closely linked. Taking advantage of this characteristic, the laboratory found through tests that if the hole is small enough, it can only allow water in the vapor state to pass through but not liquid water. Taking advantage of this characteristic, waterproof and breathable materials were invented, which use the interlacing of polyester fiber materials to form multiple tiny holes on the fabric. Taking the common waterproof and breathable material GORE-TEX as an example, the principle of this material is that there is no square There are hundreds of millions of small holes distributed in the inch. The diameter of each small hole is one 20,000 times that of a small liquid water droplet, but 700 times larger than the small state of water vapor. This is the principle of waterproof and breathable fabrics.
Waterproof and breathable fabric is a new type of textile fabric, which is made of polymer waterproof and breathable material (PTFE membrane or TPU membrane) plus fabric composite fabric. The main functions of waterproof and breathable fabrics are: waterproof, moisture-permeable, breathable, insulating, windproof, and warm. In terms of production technology, the technical requirements of waterproof and breathable fabrics are much higher than those of ordinary waterproof fabrics. At the same time, from a quality point of view, waterproof and breathable fabrics also have functional characteristics that other waterproof fabrics do not have. Waterproof and breathable fabrics not only enhance the air-tightness and water-tightness of the fabric, but also have unique breathable properties that can quickly discharge water vapor inside the structure, avoid mold breeding in the structure, and keep the human body always dry. It perfectly solves the problem of breathability, windproof, waterproof, It is a new type of fabric that is healthy and environmentally friendly.
The English name of waterproof breathable composite fabric is: Waterproof breathable composite fabric;
How waterproof breathable fabrics work:
In the state of water vapor, the water particles are very small. According to the principle of capillary movement, they can smoothly penetrate into the capillary tube to the other side, thus causing vapor permeability. When water vapor condenses into water droplets, the particles become larger. Due to the surface tension of the water droplets (the water molecules “pull and compete” with each other), the water molecules cannot smoothly break away from the water droplets and penetrate to the other side, which is to prevent Water penetration occurs, making the breathable membrane waterproof.
Note that there are two types of waterproof and breathable fabrics: water-resistant and waterproof. The former is divided into two types: fiber/cloth type (not windproof but good breathability) and membrane type (windproof but poor breathability); the latter is generally film-permeable. Type, two or three layers, windproof, two layers are softer and more breathable than three layers, while three layers are stronger. Water-resistant or highly water repellent fabrics will seep when pressure is applied to them, such as when you sit on a wet stool wearing pants made of this material.
The development of completely waterproof and breathable fabrics (waterproof) began in the late 1970s. The current second generation products are completely waterproof and windproof and maintain good breathability. However, garments made of this kind of fabric are not necessarily completely waterproof, mainly because of water seepage in seams or zippers. To ensure that the garment is completely waterproof, you need to tape all the seams (good garments use waterproof tape). This requires a lot of labor and cost, which is one of the reasons why such clothes are so expensive.
Test methods for waterproof and breathable functional fabrics
1. Cup control method
1.1 Water vapor transmission method
1.1.1 Cup correcting method
A, Chinese national standard: GB/T12704-91 B
B, American Society for Testing and Materials standard: ASTM E96 Produce B and D
C, Japanese Industrial Standard: JIS L-1099 A2
D, Canadian Standard: (CGSB)-4.2 No.49-99
E, British Standard: BS 7209-1990
1.1.2 Cup pouring method (also called moisture absorption method)
A. American Society for Testing and Materials standard: ASTM E96 BW (1995 and 2000 editions)
1.2 Desiccant method
1.2.1 Cup correcting method
A. Chinese national standard: GB/T 12704-91 A
B, Japanese Industrial Standard: JIS L-1099 A1
C, American Society for Testing and Materials standards: ASTM E-96 A, C, E
1.2.2 Cup pouring method
A, Japanese Industrial Standard: JIS L-1099 B1, B2
B, American Society for Testing and Materials standard: ASTM E-96
C, Belgian UCB company standard: UCB law
D, British Standard: B.T.T.G method
2. Sweating hot plate method, also called skin model method
A. ISO standard: ISO 11092
B. Fire protective clothing testing: NFPA 1971
C, American Society for Testing and Materials standard: ASTM F 1868-98 B
D, German standard: DIN 54 010 T01-A
3. Sweating dummy method
The sweat dummy dummy is somewhat like a hot plate and is used to simulate the shape and size of a typical human body. The dummy test is more practical than the sweaty hot plate test because it can take into account more variables.��Including the surface area of the human body covered by clothing, the number of textile layers and the distribution of the air layer on the human body surface, loose or tight fit, skin temperature differences in different parts of the human body, body position and movement status, etc. However, there has not yet been a sweat dummy that can test evaporative thermal resistance under dynamic conditions such as walking.
Currently, there are no design standards and testing procedures for sweat dummies. And because sweating dummies are more complex and expensive, dummy testing is more expensive than the hot plate method.
4. Other methods
A, Watkins method
B, Mernander method
C, Farnworth method
D, Van Beest method
E, Ruchman method
F, Gibson method
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