Fiber impregnation process and impregnated fiber formed thereby

Abstract From the Canadian patent

A method for producing a low cost impregnated and coated fiber useful in forming pump valve, expansion joint, hydraulic cylinder and similar packings capable of resisting high caustic concentrations is provided. In accordance with this method a relatively low cost yarn, such as rayon, is simultaneously subjected to a spreading operation and passed through a highly alkaline colloidal tetrafluoroethylene (TFE) solution. As the yarn fibers are spread from a fiber bundle to a flat ribbon-like array of spaced parallel fibers, the fibers swell or "balloon," thus allowing the TFE to completely penetrate the interior of each fiber. A subsequent coating step insures that the exterior of each fiber …