separation functional fibers are produced by exposing fibers with a core / sheath structure to an ionizing radiation and then grafting a polymerizable monomer to the fibers . ion - exchange fibers are produced by introducing , through radiation - initiated graft polymerization , ion - exchange groups into the sheath of each of composite fibers the core and the sheath of which are composed of different kinds of high - polymer components . the separation functional fibers and the ion - exchange fibers are useful in various applications such as the production of pure water in electric power , nuclear , electronic and pharmaceutical industries and the demineralization of high - salt content solutions in the production of foods and chemicals . the fibers are also useful in removing harmful components from gases , as well as odorous components such as ammonia .