Waterproof and breathable film principle
In the state of water vapor, water particles are very fine, and according to the principle of capillary movement, they can smoothly penetrate into the capillary to the other side (in our products, they can smoothly pass through the middle plastic layer), thus causing vapor permeation. When water vapor condenses into water droplets, the particles become larger. Due to the surface tension of water droplets (water molecules "pull each other"), water molecules can't break away from the water droplets and penetrate to the other side smoothly, that is, water infiltration is prevented, and the vapor permeable membrane has waterproof function.
Waterproof and breathable film material
Waterproof and breathable membrane technology was first introduced from Europe and America. However, the domestic production technology is varied, and the quality of products from various manufacturers is uneven, which fails to form a unified quality standard. In fact, the waterproof breathable film is mainly composed of three layers: PP spunbonded nonwoven fabric, PE polymer breathable film and PP spunbonded nonwoven fabric. The main function of spunbonded nonwovens is to enhance tension and hydrostatic pressure and protect the middle layer (breathable film). The real ventilation mainly depends on the middle layer PE polymer breathable film.
Price of waterproof and breathable film
The price of waterproof and breathable membrane is mainly composed of raw materials, production technology and equipment investment cost. At present, some domestic manufacturers distribute waterproof and breathable films as auxiliary materials, which have low cost and price, and are not higher than the main materials such as thermal insulation cotton. This is nonsense. This kind of statement is purely deceiving and misleading consumers. Because these manufacturers simply don't understand the production process of waterproof and breathable films, they use the very simple equipment of coated non-woven fabrics or hot melt adhesive spraying composite non-woven fabrics to produce fake and shoddy waterproof and breathable films, misleading consumers with fallacies and heresies, and achieving ulterior motives.
How to distinguish between true and false waterproof breathable film
1. Laboratory test
Test items: A. Temperature resistance B. Water vapor throughput (i.e. air permeability) C. Hydrostatic pressure D. Aging resistance.
The real waterproof breathable film has no compound glue, so the temperature resistance is -40, 100 degrees (EU ce standard, American ASTM standard). It is not made of polyethylene or TPO, so the air permeability should exceed 1500g/ square /24 hours. If it is made of polyethylene or TPO, it is basically airtight. According to the hydrostatic pressure test, the hydrostatic pressure of the thin waterproof breathable film is at least 1.5 m 2. Simple hands-on test.
On the surface, there are obvious pressure points on both sides of the waterproof and breathable film, which is because the production process is hot-pressed and compounded. Please note that it is not the point of the nonwoven fabric itself, but the point that obviously overlaps. To tear off the waterproof breathable film, the middle polymer layer should be a milky soft waterproof breathable layer, because it is hot-pressed and laminated, and there should be pressure points on this film. In addition, if you gently press the non-woven fabric and membrane with your hands, if you feel sticky, you can conclude that it is adhered by hot melt adhesive, then this is a fake waterproof breathable membrane. Because even if the hot melt adhesive is bonded at room temperature, these three layers of materials will bubble quickly and peel off automatically.
Waterproof and breathable membrane manufacturer
Shenzhen Nantong kangda composite material co., ltd
Kedebao building energy-saving technology co., ltd
Waterproof and breathable film structure
After selecting the waterproof and breathable membrane, the construction of waterproof and breathable membrane will begin. In the construction process, try to avoid infiltration and opening on the waterproof and breathable membrane, and try to ensure the integrity of the waterproof and breathable membrane. If opening or penetration is required, the penetration and opening shall be sealed with butyl tape.
Since the waterproof and breathable film has no obvious flame retardant effect, welding should be avoided as far as possible for curtain wall engineering connectors, and open flame operation (including welding) should be arranged before the waterproof and breathable film construction. It is strictly prohibited to carry out open flame operation (including welding construction) near the waterproof and breathable membrane.
When laying waterproof and breathable membrane, the laying method can be selected according to the actual situation. The waterproof breathable film and thermal insulation cotton are fixed with rock wool nails, and the fixed rock wool nails are sealed with butyl adhesive tape. The area of the sealing position is based on the fact that the nail head is completely covered by butyl tape.
Before construction, clean up the dust and oil stains on the corner code to ensure that the corner code is clean, so as to ensure the bonding effect between the corner code and the waterproof and breathable membrane. When the corner code passes through the waterproof membrane, the integrity of the waterproof membrane should be ensured as much as possible, and the corner code and the waterproof membrane should be completely sealed by flooding the curve of the waterproof membrane. The adhesion between the seal and the corner code is not less than 2cm.
The waterproof breathable film overlaps with the window frame and door frame, and it is used for straight-line immersion sealing, and the corner is sealed by curved immersion sealing. The bonding width between the sealing strip and the window frame and door frame shall not be less than 2cm, and the bonding width at the corner shall not be less than 10cm. The installation sequence is: lower part of door and window frame → lower corner of door and window frame → side frame of door and window frame → upper corner of door and window frame → sealing.
During roof construction, the waterproof and breathable membrane should be laid along the direction of the roof, and the overlapping length is 10cm. When the high-strength aluminum alloy bracket on the roof passes through the waterproof membrane, the joint between the aluminum alloy bracket and the waterproof membrane is sealed with butyl rubber strip. In addition, the waterproof and breathable membrane cannot be exposed to ultraviolet rays for a long time, and the external decoration project should be completed as soon as possible.
Editor's summary: