Thread Content
In the construction industry, waterproof and breathable membranes are primarily used in steel-frame and wooden buildings. The domestic market is rather chaotic; most brands promoted online do not have the capability to produce such membranes, and instead offer fake and substandard products made by simply combining non-woven fabric with glue. For reputable brands, it is recommended to refer to the **Standard Design Manual 06J925-2: Construction of Roofing and Wall Structures Using Corrugated Steel Sheets and Sandwich Panels (Part 2)**. Working principle of the waterproof and breathable membrane: In the form of water vapor, water particles are extremely small; based on the principle of capillary action, they can easily penetrate through the capillaries to the other side, thereby enabling vapor transmission. When water vapor condenses into water droplets, the particles grow larger. Due to the surface tension of the water droplets (the mutual “pulling” between water molecules), these molecules are unable to easily leave the droplets and penetrate to the other side; this prevents water from seeping through, thereby endowing the vapor-permeable membrane with waterproof properties. Materials for waterproof and breathable membranes: The technology behind waterproof and breathable membranes was first introduced from Europe and the United States. However, the manufacturing processes used for domestic products vary widely, and the quality of products produced by different manufacturers differs significantly, resulting in the absence of a unified quality standard. In fact, a waterproof and breathable membrane is mainly composed of three layers: PP spun-bonded non-woven fabric, PE polymer breathable membrane, and PP spun-bonded non-woven fabric. The main function of spun-bonded non-woven fabric is to enhance tensile force and hydrostatic pressure as well as to protect the intermediate layer (the breathable membrane); actual breathability relies on the PE polymer breathable membrane in the intermediate layer. Production processes for waterproof and breathable membranes: There are mainly three types: 1. Cast coating compounding. This process involves melting plastic particles and then bonding them together using the viscosity of the plastic itself. The downside is that it is almost impermeable to air. In 2014, it was not possible anywhere in the world to use this process to produce truly highly breathable, heat-resistant, and waterproof breathable membranes. 2. Glue spraying or scraping compounding (hot melt adhesive compounding). This manufacturing process was first used in sanitary pads, diapers, and protective clothing. Currently, almost all domestic manufacturers use this process to produce highly breathable waterproof and vapor-permeable materials. The downside is that its breathability is relatively low, as the micropores in the membrane in the middle are actually blocked by hot melt adhesive. Additionally, the most serious drawback is its very low temperature tolerance – it can only withstand temperatures of up to 60 degrees. Because this glue is actually a pressure-sensitive adhesive (stickery). A simple example is that in winter, double-sided tape has almost no adhesion and tends to delaminate, but in summer, the adhesive on the surface of the tape melts. One can imagine the quality of the waterproof and breathable membrane made using this process. During construction, as long as there is a certain temperature, the non-woven fabric will delaminate. Which construction company can guarantee that the roof will be covered right after the waterproof and breathable membrane is laid? Therefore, such waterproof and breathable membranes can only be counterfeit products of genuine waterproof and breathable membranes, and they have **no market at all in Europe and the United States. 3. Thermocompression bonding. The domestic market is currently chaotic; in fact, there are very few manufacturers that produce genuine waterproof and breathable membranes. Many factories or sellers claim that their membranes are of high quality, but almost no users realize that some of the membranes provided by these manufacturers are not waterproof at all.