Hydrogen production in the heavy ion radiolysis of polymers. 1. Polyethylene, polypropylene, poly(methyl methacrylate), and polystyrene

The production of molecular hydrogen in the radiolysis of isotactic polypro pylene (PP), poly(methyl methacrylate) (PMMA), and polystyrene (PS) with pr otons and carbon ions has been investigated. Previous experimental data on the above polymers with gamma -ray and helium ion irradiations have been co mbined with similar studies on high-density polyethylene (PE) to give a com prehensive survey of the dependence of molecular hydrogen yields on particl e linear energy transfer, LET, in the range 0.2-800 eV/nm. The radiation ch emical yields of molecular hydrogen are very dependent on LET and generally increase with increasing LET. However, the relative change in hydrogen yie ld as a function of LET is very different for the various polymers. It appe ars that with increasing high LET the hydrogen yields for each of the polym ers are approaching the same value. This observation suggests that the radi olytic source of molecular hydrogen is similar for all of the polymers and increases with increasing LET of the irradiation. Unexpectedly high yields of molecular hydrogen can have implications in many fields including those that involve heavy charged particles and intense photon sources.