Use of High-Energy Radiation in Polymer Blends Technology
Exposure of organic systems to high-energy radiation (radiolysis, radiation processing) at room temperature leads to the formation of ions and free radicals. These species, in turn, react to give stable products, often through other free radicals and meta
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USE OF HIGH-ENERGY RADIATION IN POLYMER BLENDS TECHNOLOGY
Ajit Singh1 and Kamarudin Bahari2
1
AECL, Whiteshell, Laboratories, Pinawa, Manitoba, Canada
2
Nuclear Energy Unit, Kompleks Puspati, Malaysia
Abstract Exposure of organic systems to high-energy radiation (radiolysis, radiation processing) at room temperature leads to the formation of ions and free radicals. These species, in turn, react to give stable products, often through other free radicals and metastable species. The course of their reactions is influenced by the conditions under which the system has been radiation processed; for example, in the presence of oxygen, oxidative degradation predominates. The course of the reactions can also be influenced by the presence of other additives. Ambient temperature processing and the ability to change the course of resulting chemical reactions by suitable additives have been important factors in the attraction of this technology for the polymer industry. The major industrial applications of this technology in the field of polymers are based on (i) polymerization, (ii) crosslinking, (iii) scission, and (iv) sterilization of medical disposables. Radiation processing of polymer blends can lead to crosslinking or scission of one or more components, or even to inter-phase (inter-polymer) crosslinking. These effects modify the blends’ properties. Many research groups have been working on radiation processing of polymer blends, to stabilize the phases and improve performance. The polymers that have been used in the radiolytic studies of blends include polyethylene (PE), polypropylene (PP), ethylene propylene rubber (EPR), polyvinyl chloride (PVC), polystyrene (PS), and polymethylmethacrylate (PMMA). The primary aim of this chapter is to summarize the literature on radiation processing of polymer blends, to highlight the achievements, and to discuss the problems encountered. The text is preceded by brief descriptions of relevant radiation chemistry of organic compounds and known effects of high-energy radiation on the leading polymers used in blends, with the aim of enabling future workers to draw upon this knowledge in the design of experiments, in industrial applications, or both. The effects of radiation processing, first of commodity resin blends, then on the engineering and specialty resin blends, are discussed. L.A. Utracki (Ed.), Polymer Blends Handbook, 757-859. © 2003 Kluwer Academic Publishers. Printed in the Netherlands.
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Introduction
Radiation processing involves the use of natural and manufactured sources of high-energy radiation on an industrial scale, to give products that are safe, practical and beneficial [Silverman, 1981]. In comparison to conventional methods, radiation processing is an energy-conserving and environmentally benign technology. The number of electron accelerators in the industrial use has been steadily increasing despite the fact that radiation-based technologies face close scrutiny by society and regulators [Saunders, 1988; Machi, 1989; Leemhorst a
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