Recent advances in the radiation chemistry of polymers

Radiation chemical yields, G values, for scission and crosslinking in a variety of polymers have been determined indirectly from measurements of soluble fractions using a gel permeation chromatography technique and directly from solid-state 13C NMR spectra. Similar G values have been obtained by both methods for amorphous ethylene-propylene copolymers, indicating random spatial distributions for scission and crosslinking, whereas much greater crosslinking yields have been obtained by NMR in polydiene rubbers and attributed to clustering of crosslinks. Greatly enhanced degradation indicated by increased creep rate and decreased time to failure has been found for irradiation of amorphous thermoplastic polymers, including high-performance polyarylene sulfones, below their glass transition temperatures, Tg, while subjected to tensile stress; this has significant implications for the use of polymer materials in structural applications in radiation environments. (author). 12 refs, 6 figs