Gas production in the radiolysis of poly(vinyl chloride)

The yields of H2 and Cl- were determined in the radiolysis of deaerated, aerated, and water mixtures of poly(vinyl chloride) (PVC) powders with gamma-rays and 5 MeV He ions. H2 yields with gamma-rays are low at about 0.25 molecule/100 eV and they double with He ion radiolysis indicating a second order formation process. The production of H2 in the gamma-radiolysis of water-PVC mixtures is much greater than expected from the weight fraction of the components and is due to acidification of the aqueous phase by the evolution of HCl from the polymer. Cl- yields in the gamma-radiolysis of PVC with number average weights of 22,000, 47,000, and 99,000 Daltons are 19.6, 33.8, and 32.5 atoms/100 eV. Cl- continuously evolves from the polymer for days following radiolysis. The extremely large yields suggest that a chain process involving radicals stabilized on the polymeric chain are responsible. Reflectance UV/vis and infrared spectroscopy show subtle changes in the PVC with radiolysis while UV/vis absorption spectra clearly indicate the formation of polyenes with 1 to 11 units. Cl- formation is probably initiated by Cl radical production followed by an electron rearrangement mechanism along the PVC chain to produce more Cl- and polyenes.