What is waterproof breathable functional fabric? How is it tested!
Introduction to waterproof and breathable functional fabrics
When you go hiking, it will rain unexpectedly, so you can’t go up the mountain with an umbrella. Mountain climbing is also a very physically demanding sport and requires a lot of sweating. The temperature on the mountain is usually very low, so you can’t take off your clothes. So, how can we solve this kind of problem at once? In fact, people have been studying this issue for a long time, that is, wearing clothes that are both waterproof and breathable. (People often call it breathable fabric, but it is not the gas in the air, but the steam evaporated from sweat).
Specifically speaking, waterproof and breathable fabric means that water does not penetrate into the fabric under a certain pressure, but the sweat emitted by the human body can be transmitted to the outside world in the form of water vapor through the fabric, thereby preventing sweat from accumulating and condensing on the body surface and the fabric. In order to maintain the comfort of clothing, it is a high-tech, unique functional fabric. Waterproofing is not a problem for ordinary fabric workers. The key is how to achieve moisture permeability. Next, let’s take a deeper look at the types of waterproof and breathable fabrics.
1. Achieve moisture permeability through fiber
1. Ventel fabric. The earliest waterproof and breathable fabric is the famous Ventile fabric. It was designed by the British Shirley Research Institute in the 1940s. It uses high-count, low-twist pure cotton yarn from Egyptian long-staple cotton and high-density heavy-weight flat weave fabric. It was initially mainly used for cold protection for British Air Force pilots during the Second World War. Soak. When the fabric is dry, the gaps between the warp and weft yarns are larger, about 10 microns, which can provide a highly moisture-permeable structure; when rain or water hits the fabric, the cotton yarns expand, reducing the gaps between the yarns to 3 to 4 microns. This closed-cell mechanism is combined with a special water-repellent finish to ensure that the fabric is not further penetrated by rainwater. At present, this type of fabric has long been replaced by other waterproof and breathable fabrics.
2. Coolmax fabrics. Major international companies such as DuPont and Japan’s Toray have researched the method of creating pores inside the fiber to discharge sweat from the body, which is the moisture-absorbing and sweat-wicking fabric on the market. The production technology of this type of fiber is concentrated in the hands of such large international companies, and the price is relatively high, making it difficult to become the mainstream of the market.
2. Achieve moisture permeability through coating
Use dry direct coating, transfer coating, foam coating, phase inversion or wet coating (solidified coating) and other process technologies to combine various A coating agent with waterproof and moisture-permeable functions is applied to the surface of the fabric, so that the pores on the surface of the fabric are closed or reduced to a certain extent by the coating agent, thereby obtaining waterproof properties. The moisture permeability of fabrics is determined by the microporous structure formed by a special method on the coating or the interaction between the hydrophilic groups in the coating agent and water molecules. With the help of hydrogen bonds and other intermolecular forces, water molecules are adsorbed on the high-humidity side, and then Pass to the low temperature side to obtain the analytical action. Coated fabrics are widely used because they are low in price and achieve a certain degree of moisture permeability. However, due to its poor waterproof and breathable performance and unsatisfactory feel, its market share is gradually decreasing.
The wet transfer coating fabrics now developed have given coated fabrics a new lease of life. Not only do they have high physical properties such as waterproofing and moisture permeability, the surface fabric can be treated with 100% Teflon, and its washing fastness can be Reached more than 25 times, the feel is also very good.
3. Achieve moisture permeability by laminating waterproof and moisture-permeable membranes
1. PTFE film
The diameter of water vapor molecules is 0.0004 microns, while the diameter of small mist in rainwater is 20 microns, drizzle The diameter of the film is already as high as 400 microns. If a film with a pore diameter between water vapor and rainwater can be produced, wouldn’t it be possible to achieve both waterproofing and moisture permeability? The American GORE company became the first company to produce this membrane using polytetrafluoroethylene (PTFE). It was laminated with fabric and named GORE-TEX. However, because PTFE is very chemically inert, there are few materials that can laminate it well with other fabrics, resulting in very poor fabric fastness. Later, after continuous efforts, it was combined with other hydrophilic film layers to form a composite film, and special treatment was performed on the film, so that the fastness was greatly improved. It is generally believed that the water pressure of Gore-Tex fabric can reach 10,000mm, and the water pressure will drop significantly after washing 6-7 times; the moisture permeability can reach 10,000g/sqm*24hrs, but this is not the case with just made fabrics. To reach this value, it takes several washings to remove part of the glue, increase the available pores, and increase the moisture permeability.
PTFE fabrics are now mainly represented by Gore and Donaldson from the United States. Gore produces and laminates its own films and does not sell films separately. It designates better clothing manufacturers to make clothing and has separate sales staff to cooperate with them. Donaldson only produces films and laminates them at Japanese laminating manufacturers. The competition between these two companies in the market is also very fierce. Domestic PTFE manufacturers are also gradually emerging, but they mainly use single-component PTFE films without compounding with hydrophilic films, and the washing fastness is generally only about five times. Last time I met an Indonesian manufacturer at the Shanghai Industrial Fabrics Exhibition, it was said that the products were washed about five times.
Although the waterproof and breathable performance of PTFE fabric is better than other fabrics, due to its chemical inertness, the film is difficult to be degraded by nature, and the combustion temperature is as high as 405°C. Large-scale application makes GORE-TEX has gradually become an environmental killer. Faced with such a problem, GORE established a waste clothing recycling mechanism called Balance Project in order to reduce its impact on the environment. I hope that GORE can continue to move forward firmly as environmentalism becomes more and more popular.
2. TPU film
TPU is the abbreviation of thermoplastic polyurethane film, which is a non-porous hydrophilic film. Since the film itself has no pores, the waterproof effect is naturally very good, and it also makes the fabric windproof and warm. Moisture permeability is mainly achieved through its hydrophilic properties. It relies on the difference in vapor pressure inside and outside the clothes to transfer steam from places with high pressure to places with low pressure, thereby achieving the function of moisture permeability. I have also been engaged in the production of TPU composite fabrics for a long time, so I will give a brief introduction.
Product properties:
A. Green and environmentally friendly
B. Excellent breathability and moisture permeability
C. Absolutely waterproof, anti-blood stain, antibacterial
D. Windproof and cold-resistant, anti-velvet, Smooth
E. Durability, super water-repellent finish
F. Easy decontamination finish, can be washed normally
Scope of application:
A. Field military uniforms, firefighting, military special clothing
B .Protective equipment, military tents, sleeping bags and postal bags
C. Sports clothing for mountaineering, skiing, golf and other sports
D. Materials for shoes and hats, bags, blackout curtains, anti-UV umbrella cloth
E. Rainproof, breathable ponchos, casual windbreakers
F. Medical supplies
Product specifications:
1. Door width: 1500mm
2. Product thickness: 0.012~0.025mm
3. Low Transparent film, low fog permeability mask, low milk permeability white film
Moisture permeability index: greater than 1000g/m2*24hrs (ASTME96BW2000 version)
Hydrostatic pressure resistance index: greater than 10000mmH2O (AAASE3RETRUY7I8OFGTCC127)
4. Medium Transparent film, medium mist mask, medium translucent white film
Moisture permeability index: greater than 3000g/m2*24hrs (ASTME96BW2000 version)
Hydrostatic pressure resistance index: greater than 10000mmH2O (AATCC127)
5. High Transparent film, high mist-permeable mask, high milk-permeable white film
Moisture permeability index: greater than 5000g/m2*24hrs (ASTME96BW2000 version)
Hydrostatic pressure resistance index: greater than 10000mmH2O (AATCC127)
6. Suitable Lamination of various fabrics such as knitted, woven, non-woven fabrics
The most common TPU composite fabrics on the market are:
1. Four-way elastic + TPU + polar fleece, which is what people often Called SoftShell. The four-sided elastic is mainly 75D (for women’s clothing) and 100D (for men’s clothing), and the polar fleece is mainly 75D/72F and 100D/144F. It can have many styles such as plain weave, twill weave, plaid, etc. Because it is waterproof, breathable, windproof and warm, its use is no longer limited to ordinary outdoor sportswear. Many large foreign companies use it as work clothes for their employees. One of my Japanese customers actually used it as a ramen restaurant waiter’s work clothes!
2. Chemical fiber woven fabric + TPU + Tricot (polyester warp knitted mesh fabric). Woven fabrics mainly include pongee, taslan, oxford, peach skin, nylon, etc. Ordinary ones such as 228T Taslan can be used as the main fabric of jackets; nylon camouflage printed fabrics can be used as military clothing; fluorescent fabrics can be used as police uniforms and other work clothes; AA
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