Method For Realizing Moisture Permeability Function Of Waterproof Breathable Fabric
May 14, 2020
1. Moisture permeability through fiber
1. Ventel fabric. The earliest waterproof and breathable fabric was the famous Ventile fabric. It was designed by the Shirley Institute in the UK in the 1940s. It uses high-count low-twist cotton yarn with high density and heavy flat weave from Egyptian long-staple cotton. It was originally mainly used for the cold protection of British Air Force pilots during World War II Anti-dip clothing. When the fabric is dry, the gap between the warp and weft yarns is large, about 10 microns, which can provide a highly moisture-permeable 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 This closed-cell mechanism is combined with a special water-repellent finish to ensure that the fabric is not further penetrated by rain. At present, this kind of fabric has been replaced by other waterproof and breathable fabrics.
2. Coolmax fabrics. International companies such as DuPont and Toray Japan have researched the method of making holes in the fiber to remove sweat from the body, which is the moisture wicking fabric on the market. This type of fiber production technology 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.
Second, through the coating to achieve moisture permeability
Using dry direct coating, transfer coating, foam coating, phase inversion or wet coating (solidified coating) and other process technologies, various coating agents with waterproof and moisture permeability functions are applied to the fabric On the surface of the fabric, the pores on the surface of the fabric are closed or reduced to a certain degree by the coating agent, thereby obtaining waterproofness. The moisture 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 the water molecule. With the help of hydrogen bonding and other intermolecular forces, the water molecule is adsorbed on the high humidity side Obtained by the analysis function transferred to the low temperature side. Coated fabrics are low in price, have achieved a certain degree of moisture permeability, and are widely used. However, due to its poor waterproof and moisture-permeable performance and unsatisfactory feel, the market share is gradually decreasing.
The wet transfer coating fabric developed now makes the coated fabric renewed. It not only has high physical properties such as waterproof and moisture permeability, but also can be treated with 100% Teflon, and the washing fastness can reach 25 times. Above, the feel is also very good.
3. Moisture permeability is achieved by laminating waterproof and moisture permeable membranes
1. PTFE film
The diameter of the water vapor molecule is 0.0004 microns, and the diameter of the lightest mist in the rain water is 20 microns. The diameter of the drizzle has been as high as 400 microns. If a film with a pore diameter between water vapor and rain can be manufactured, it is waterproof. Isn't it possible to achieve moisture permeability? The American company GORE used polytetrafluoroethylene (PTFE) to become the company that produced the film. After the composite lamination with the fabric, the trade name was GORE-TEX. However, because PTFE is very chemically inert, there are few materials that can be laminated well with other fabrics, and the fabric fastness is very poor. Later, after continuous efforts, by sub-combining with other hydrophilic film layers into a composite film, and special treatment on the film, the fastness is greatly improved. It is generally believed that the water pressure of Gore-Tex fabrics can reach 10000mm, and the water pressure only drops significantly after 6-7 washings; the moisture permeability can reach 10000g / sqm * 24hrs, but this is not achieved by the fabric just made This value needs to be washed several times to remove some of the glue. The available pores increase and the moisture permeability increases.
PTFE fabrics are mainly represented by Gore and Donaldson in the United States. Gore produces its own film and makes composites. Instead of selling the film separately, it appoints a better clothing manufacturer to make the clothing and has a single salesperson to cooperate with it. Donaldson only produces thin films, which are compounded by Japanese compound manufacturers. The competition between these two companies in the market is also very fierce. Domestic PTFE manufacturers are gradually emerging, but they are mainly based on single-component PTFE films, which are not compounded with hydrophilic films, and the washing fastness is generally only about five times. Last time I met an Indonesian manufacturer at the Industrial Fabrics Exhibition in Shanghai, and it was said that it was washed about five times.
