To achieve this dual functionality, engineers have developed hybrid fabrics that incorporate elastic fibers, such as spandex or elastane, into the base structure. These fibers give the waterproof stretch tent fabric its distinctive stretch and flexibility, allowing it to adapt to different shapes and surfaces. At the same time, waterproof coatings or membranes, such as polyurethane (PU) or thermoplastic polyurethane (TPU), are applied to the fabric’s surface. These coatings create an impermeable barrier that prevents water from penetrating the fabric, ensuring it remains dry even during heavy rainfall. https://www.kaidali-fabric.com/news/industry-news/how-to-test-and-ensure-the-waterproofing-of-your-tent-fabric.html