Radiation Chemistry of Polymers

Abstract

Polymeric materials are exposed to high energy radiation either deliberately to alter their properties or inadvertently during their use in high dose environments. As a consequence, an understanding of how radiation modifies the polymer structure, and hence properties, is essential for many applications. In addition, the understanding of the degradation of polymers with light or heat can benefit from knowledge of the reaction pathways of radical and charged species formed on irradiation with high energy photons. This article aims to provide a broad overview of the fundamental processes occurring during radiolysis of polymers. This is achieved through a discussion of the interaction of high energy photons with matter, and the subsequent reactions of mainly radical intermediates. Polymers either cross‐link or degrade on exposure to radiation, and the final properties of the polymers depend critically on the balance of these two main reaction pathways. A number of examples are taken from the literature to illustrate how the tendency to undergo cross‐linking or main‐chain scission depends on the polymer structure. The overall yield of reactions can be greatly reduced by the introduction of aromatic groups into the polymer structure. On the other hand, yields can be increased by the inclusion of radiation‐sensitive groups such as sulfones. Similarly, the rates of reactions and the balance between cross‐linking and scission can depend sensitively on the radiolysis temperature. While this review focuses on a discussion of the reactions occurring on radiolysis in vacuo, the effect of the presence of dissolved oxygen on the reaction pathways is also discussed.

Structure of Polytetrafluoroethylene Modified by the Combined Action of γ-Radiation and High Temperatures

“…There are different points of view on the course of changes in the microstructure of PTFE during high-temperature radiation treatment for example, the decisive role of crosslinking processes is discussed in [65]. However, at the same time there are arguments in favor of amorphization and the accumulation of defects during irradiation of PTFE [66].…”

A Quantum-Based Approach to Predict Primary Radiation Damage in Polymeric Networks

“…Chemical degradation of polymer materials is thought to arise from networkaltering reactions such as chain scissions and formation of cross links, which can lead to macroscopic mechanical changes including permanent set, embrittlement, or breaking under load. 2,7,8 Experimental diagnostics that probe chemical degradation are often indirect and capture highly integrated responses from which it can be hard to infer fundamental chemical events, for instance measuring viscosity, gelation, stress-strain responses, vibrational spectra, or evolved o-gassing products.…”

Composites Containing Ag Nanoparticles for X-ray Protection

“…Polymer nanocomposites are progressive functional materials [12][13][14] composed of nanoparticles dispersed inside of polymer matrix and covered by polymer, thus forming a skeleton structure. Produced nanocomposites combine the eligible properties of both agents [1,15,16].…”

“…Polymer composites are appealing expectants for ionizing radiation armor applications and can be made transparent. In order to capitalize on the superior properties of polymer composites in transparent armor applications [12], novel techniques and fabrication/modification methods are needed. Modification of polymers with high energy radiation (X-rays, gamma rays, electron beam) leads to the formation of new bonds, free radicals, oxidized products, grafts, scission of main chains and cross-linking [12,14,21,26,27].…”