Waterproof breathable outdoor fabrics work to keep you and your layering system dry while allowing perspiration to exit during exertion. Waterproof breathables typically offered in 2-3 layer fabrics, all of which are all built upon the same principle: the pores of these fabrics are too small for water to get through, but large enough for body vapor to escape. To attain their waterproof breathable properties, fabric makers utilize either laminate technology or coatings.Laminates are formed when waterproof breathable membranes are bonded directly to the underside garment’s face fabric. An analogy for this process is the idea of wallpaper applied to a wall.Coatings are liquid solutions that provide waterproof breathable characteristics when applied to the face of the garment, similar to paint applied to a wall. All raingear face fabrics are treated with durable water repellent finishes to provide extra water protection.Waterproof breathables commonly consist of an outer layer known as a face fabric usually made of nylon or polyester and a laminated membrane or coating made of.
A third layer consisting of a backer lining is sometimes added to provide abrasion resistance. The purpose of the face fabric is to add color and protection. Although this layer is treated with a durable water repellant , it is not waterproof. The second layer , the membrane, which has tiny holes too small to let liquid water enter, but large enough to allow water vapor to escape, is the waterproof layer. The last layer in layer fabrics is bonded for comfort. Over the years most waterproof breathable fabrics are all extremely waterproof for any weather activities, but differ in breathability and other dimensions.That means the individual atoms of the membrane are tightly bound to one another. A low surface energy solid will only get wet when it comes into contact by a low surface energy liquid. Water has a high surface energy; atoms in water, while still bound, are not bounded to the same magnitude as low surface energy liquids. When a liquid has high surface energy, molecules tend to pull together in a shape that occupies the least amount of space on other surfaces.
There are only two ways that water can penetrate if water is applied with enough force or if the ePTFE membrane is contaminated. Rain during windy seasons exerts a force of about 2 pounds per square inch, which is not strong enough to penetrate. Any high surface energy materials can cause contamination dirt, body oils, sweat, or pesticides. When the membrane is contaminated, the composition of the membrane is altered, causing its surface energy to change. If water molecules come into contact with a high-energy surface, they split open and wet the surface of the material causing leakage.It is hard to discuss waterproof breathable laminates without mentioning. Robert W. Gore discovered that ePTFE could be manipulated into a nearly weightless film, thinner than a trashcan liner. This membrane contained billions of microscopic pores that turned out to be so small, water droplets couldn’t fit through, but water vapor-that is released from the body when you sweat- could.
Thus, the creation of waterproof breathables. PU laminates tend to have many characteristics that set them apart from other waterproof breathable laminates. Some of these general characteristics are long-term durability, flexibility. Additionally, PU laminates are abrasion and oil resistant. Tensile strength measures the stress a material can withhold before breaking while being stretched. The tensile strength of PU laminates can range from 5800 to 9506 psi (pounds per square inch) while the tensile strength of other laminates is around 4000. PU laminates can elongate 800% before breaking compared to the 300% of other laminates. PU laminates possess application flexibility, which means they can be transformed and altered while still retaining flexibility and performance. These laminates remain flexible in temperatures as low as -60°F, which makes them the perfect material for demanding environments.
