Radiation effects on polymers

In this brief section, we have not touched the vast field of radiation-induced polymerization and radiation effects on polymers. Fortunately, the field has been surveyed very well in international conference proceedings published in Radiation Chemistry and Physics referred in the beginning of this section. The earlier books by Charlesby (1960) and by Dole (1973) provide adequate background information. 

Research studies of radiation effects on polymer materials are normally carried out on samples in powder, granule, film or sheet form in a completely unstressed condition. 

LOV MOLECULAR WEIGHT MODEL COMPOUNDS. The mechanisms of radiation effects on polymers are frequently investigated by studies of low molecular weight model compounds. Analysis of the chemical reactions is much easier than with high molecular weight polymers. Thus, N-acetyl amino acids can be studied as model compounds for poly(amino acid)s and hence for proteins. 

Much research into radiation effects on polymers is done with samples sealed under vacuum. However, polymer materials may, in practical applications, be subjected to irradiation in air. The effect of irradiation is usually substantially different in air, with increased scission at the expense of crosslinking, and the formation of peroxides and other oxygen-containing structures. Diffusion rates control the access of oxygen to radicals produced by the radiation, and at high dose rates, as in electron beams, and with thick samples, the behaviour may be similar to irradiation in vacuum. Surface changes may be quite different from bulk due to the relative availability of oxygen. 

The species present in polymers that can be studied by ESR are often highly reactive, short-lived and are present in low concentrations. However, developments in instrumentation have offered improvements in sensitivity and,combined with more reliable interpretation of data (1), the increasing application of this method of polymer characterization in studying radiation effects on polymers can be expected. 

Radiation Effects on Polymers for Biological Use Volume Editor Kausch, H. 

Basic and applied researches on charged particle and photon-induced reactions of polymers are surveyed. The basic parts are fundamentals of radiation effects on polymers and pulse radiolysis studies on polymers. The intermediate parts are a great diversity of radiation effects on polymers and reaction mechanisms of electron beam (EB) and x-ray resists. The applied parts are economic scale of utilization of radiation and industrial application of radiation to polymers. 

RADIATION-INDUCED REACTIONS IN POLYMERS 3.1. Fundamentals of Radiation Effects on Polymers... 

Classical investigations of radiation effects on polymers have been summarized in some books or review articles in the 1970s to the 1990s [29,62-64]. Many of the works were focused... 

Radiation effects on polymers are more subtle than normal radiation chemistry, in that small chemical changes may have pronounced effects on the physical properties. Because of the sensitivity of these physical properties, the radiation chemistry of Polyox is best discussed in two parts—the chemical reactions occurring and the effects of these reactions on the physical properties. 

Harrington, R. "Radiation Effects on Polymers." Rubber World 88, 3 (1960) 475. 

Polyethylene is known as one of the typical polymers which crosslink under the influence of ionizing radiation. The radiation-induced crosslinking (the formation of C-C covalent bonds between polymer chains) of polyethylene has long attracted the interest of a large number of research workers, because this polymer has the most simple chemical structure for the fundamental study of radiation effects on polymers, and also because the irradiation with ionizing radiation is a practically important means of modifying the mechanical and thermal properties of polyethylene. 

The meeting on radiation effects on polymers was held at the Radiation Laboratory at the University of Notre Dame to review and discuss advances in the radiation processing of polymers. The trends in the basic research, R D and industrial applications were reported. 

GINSBERGEN J., OVERBERGH N., Radiation effects on polymer blends, in Radiation processing of polymers (eds SINGH A., SILVERMAN J.) Hanser - Oxford Univ.Press, Munich - New York, 1992. 

Additional work was performed by Gardner (Refs 92 99) on proplnts for future missions in space. A PBAA AP/Al proplnt, an aluminized double-base proplnt, and a polyurethane—AP/Al proplnt were studied as a function of Co radiation, with a dose rate of 2.54 x 10 R/hr and total doses ranging up to 1.5 x 10 R. The effects were noted on tests with the burning rate, tensile stress, elongation modules and hardness of the three materials. The PBAA proplnt withstood 1.5 X lO R. On the tensile strength, the double base and polyurethane decrease significantly at a dose of 4 x 10 R. On elongation, the double base decreased on stress at max strain after 10 R, while the polyurethane pro-pint decreased on modulus and hardness after a dose of 10 R. Estimates of the radiation effects on polymers are listed in Table 19... 

Burg, K. J. L. and Shalaby, S. W., Radiation sterilization of medical and pharmaceutical devices, in Radiation Effects on Polymers Chemical and Technological Aspects, American Chemical Society, Washington, DC, 1996, 240. 

Tagawa, S. In Radiation Effects on Polymers. ACS Symposium Series 475, Clough, R.L., Shalaby, S.W., Eds. American Chemical Society Washington, DC, 1991 2 pp. 

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