Nonwovens refer to paper-like structures made from non-cellulose fibers (such as polymer, ceramic, glass, metal, alloy, and carbon fibers).
During the wet-lay process, the fibers are dispersed in liquid, and the liquid is drained through a screen (on a handsheet mold or continuous paper machine). As the stock or slurry passes through the screen, the fibers are deposited on the screen. Then as more stock runs through the process, it is directed by fluid dynamic forces to the places where the least amount of fiber has been previously deposited. This fills in light spots and prevents heavy spots from forming. This action is referred to as “self-healing,” and as a result, the wet-lay method produces sheets with better than three times the uniformity of air-laid sheets.
Since no hydrogen bonding takes place with noncellulosic fibers, an alternative bonding method is necessary. The method most commonly employed by IntraMicron is to sinter the nonwoven at high temperature, which results in very strong bonds. Sintering takes place below the melting point of the fiber, but close enough to that point to cause solid phase welding at the points where fiber crosses fiber. An alternative bonding method is using a chemical binder, but for IntraMicron's products this method is not typically used because of its interference with chemical reactions, sorbents, and catalysts.
The typical wet-lay process produces a sheet with a 95% void volume before calendaring (pressing). IntraMicron has developed a method to produce 98% void thermally conductive media that can be sintered to entrap catalysts and sorbents. This allows for the manufacturer of extremely active (endothermic and exothermic) catalyst structures that have the ability to maintain remarkably consistent temperature profiles.