Polymers Under Ionizing Radiations: Concepts and Applications

Abstract

Introduction Since their industrial development in the 20th century, the use of polymers in various fields is widespread and the electronuclear industry is no exception. Here, polymers are submitted to ionizing radiations during their use and irradiation is considered negative. Polymers in the electronuclear industry are encountered in various applications, be it for surface or human protection, as insulation sheaths for electric cables, or as paints in the reactor building. In this realm, these materials are submitted to ionizing radiations either during or after their use, especially for those contaminated by radionuclides. For most of these usages, nuclear security is at stake. Besides, ionizing radiations are used deliberately for medical appliance sterilization, for material processing (curing), or for new materials design through, for example, Ion Track Technology, or radiation-induced synthesis. Whatever the reasons why polymers are submitted to ionizing rays, a thorough knowledge of their evolution as a function of the irradiation conditions (dose,1 dose rate,2 radiation types, irradiation temperature, and environment) is mandatory either to determine the right conditions of use (aging level) or the optimal conditions for material design. First, what are polymers and which of their features can influence their behavior under irradiation? Polymers are macromolecules made of long chains of repetition units obtained through the covalent bonding between monomers. They present various levels of organization—molecular, macromolecular, and supra-macromolecular—associated with various mobility levels and thus to various transitions and relaxations types and related temperatures. Polymers are semicrystalline materials, meaning that they contain crystalline domains organized in an amorphous matrix (Figure 1). This leads to a multiphase material composed of phases with almost opposed characteristics in terms of reactive species and chain mobility, gas diffusion, and so on. Polymers are complex materials to study under ionizing radiations, as they differ by the chemical structure of the monomers (repeating unit), their organization along the backbone, and the resulting microstructure. Therefore, herein, we will intentionally present concepts and give specific information as examples when needed. We will focus on the parameters affecting their evolution under ionizing radiations and present some applications using polymer modifications under ionizing radiations.