Waterproof and moisture-permeable fabric means that water does not soak into the fabric under a certain pressure, but the sweat emitted by the human body can be transmitted to the outside world through the fabric in the form of water vapor, so as to avoid the accumulation of sweat and condensation between the body surface and the fabric to keep the clothing comfortable. 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. Below, we learn about two fabrics that achieve moisture permeability by laminating waterproof and moisture-permeable membranes, PTFE film and TPU mesh fabric.
1. PTFE film
The diameter of water vapor molecules is 0.0004 microns, while the diameter of the smallest mist in rain is 20 microns. The diameter of drizzle is as high as 400 microns. If a film with a pore diameter between water vapor and rainwater can be created, it will be waterproof. Wouldn't it be possible to achieve moisture permeability again? The American GORE company used polytetrafluoroethylene (PTFE) to become the first company to produce the film, which was compounded and laminated with the fabric to take the trade name GORE-TEX. But because PTFE is very chemically inert, there are few materials that can laminate it well with other fabrics, and the first-generation fabrics have very poor fastness. Later, after continuous efforts, the fastness is greatly improved by sub-combining with other hydrophilic film layers to form a composite film, and carrying out special treatment on the film. It is generally believed that the water pressure of Gore-Tex fabrics can reach 10,000mm, and the water pressure will only drop significantly after 6-7 washes; the maximum moisture permeability can reach 10,000g/sqm*24hrs, but this is not the case with just-made fabrics. To reach this value, it needs to be washed several times to remove part of the glue, the available pores will increase, and the moisture permeability will increase.
PTFE fabrics are now mainly represented by Gore and Donaldson in the United States. Gore produces and laminates the film by itself. Instead of selling the film alone, Gore appoints a better clothing manufacturer to make clothing, and has a single salesperson to cooperate with it. Donaldson only produces thin films, which are laminated at a laminating factory in Japan. The competition between the two companies in the market is also very fierce. Domestic PTFE manufacturers are also gradually emerging, but they are mainly single-component PTFE films, not compounded with hydrophilic films, and the washing fastness is generally only about five times. The last time I met an Indonesian manufacturer at an industrial fabric exhibition in Shanghai, it was said that it was washed about five times.
Although PTFE fabric has better waterproof and moisture permeability than other fabrics, but also due to its chemical inertness, the film is difficult to be degraded by nature, and the combustion temperature is as high as 405 ℃. Large-scale application makes GORE-TEX gradually become the killer of the environment. Faced with this challenge, GORE has established a recycling mechanism for discarded clothing called the Balance Project to reduce its impact on the environment. It is hoped that today, when environmentalism is popular, GORE can go on firmly.
2. TPU film
TPU is the abbreviation of thermoplastic polyurethane film, which belongs to non-porous hydrophilic film. Since the film itself has no pores, the waterproof effect is naturally good, and it also makes the fabric windproof and warm. Moisture permeability is mainly achieved through its hydrophilic properties, relying on the difference in steam pressure inside and outside the clothes to transfer steam from places with high pressure to places with low pressure, thereby realizing the function of moisture permeability. I have also been engaged in the production of TPU composite fabrics for a long time, and I will make some brief introductions.
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