Radiation-induced Oxidation of Polymers

A polymer is a macromolecule formed by the combination of simple molecules, monomers, of low molecular weight. A polymer molecule usually has at least 2000 atoms linked by covalent bonds. In general, polymers can be divided into inorganic and organic, and also into naturally occurring and synthetically produced. Polymers may contain additives such as dyes, fi llers, antioxidants, fl ame retardant materials and other components needed to carry out their use in many application areas. The properties of polymers largely depend on both their microstructure and macrostructure. Ionizing radiation excites active species, like radicals. In the radiation processing of polymers, usually two kinds of radiation are used: (i) high energy electrons from accelerators, which give continuous and homogeneous radiation, but have limited penetration depth, and are a source of high doses of radiation per unit of time, and (ii) gamma rays from radionuclides of cobalt-60 and cesium-137, which more deeply penetrate materials and give relatively small doses of radiation per unit of time.