The Effect of Nuclear Radiation on Fibrous Materials

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Abstract
Dacron polyester filaments of different draw ratios were prepared and were exposed to high-energy radiation from two sources. Exposure both in a reactor and to a Cobalt-60 source resulted in an increase in the moduli of elasticity of the filaments. This indicated that cross-linking reactions took place and predominated over chain scission, particularly during the early stages of irradiation. Draw ratio, i.e., the degree of orien tation of the filament, had an influence on the behavior. The materials of lower draw ratio tended to show more cross-linking than those of high draw ratio, the optimum being between 2.5:1 and 3.0:1. The degree of cross-linking in Dacron under the conditions of these experiments was, however, of a low order of magnitude. The solubility of the filaments was decreased only slightly, and the melting point remained unchanged. The degree of crystallinity of the filament did not influence the behavior of the filaments. Although the work has not yet been extended to many other polymers, it is believed that materials which show a marked tendency to cross-link during exposure to high- energy radiation would show an effect similar to Dacron. For example, polyethylenes of different degrees of orientation or of different pretreatments might well behave quite differently with respect to changes in properties brought about by a given level of radi ation. This has been partially substantiated by some preliminary results obtained with polyethylenes of unknown history, but at the same time known to be different in character prior to irradiation.

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