Dynamic evolution of cases in the gamma- and helium-ion radiolyses of solid polymers

The dynamic evolution of gaseous hydrogen, methane, and carbon dioxide in t he gamma- and He-4-ion radiolyses of solid polymers was investigated. The p olymers used include low-density and high-density polyethylene, polypropyle ne, polystyrene, poly (methyl methacrylate), Nylon 11, Nylon 6, and poly(di mer acid-co-alkyl polyamine). An inline quadrupole mass spectrometer was ut ilized to monitor the dynamic profiles of the gases produced in the radioly sis. One- and two-dimensional numerical diffusion models were developed to simulate and extract optimum diffusion coefficients and gas yields from the experimental dynamic gas profiles. It was found that the dynamic evolution of molecular hydrogen from the bulk polymer is controlled by its diffusion in most cases, such as CO2 in poly(methyl methacrylate). In the gamma radi olysis of some polymers such as low-density polyethylene and polypropylene, the dynamic evolution of methane is only partially controlled by the diffu sion process, and some other postirradiation process is a factor. It is con cluded that the simulation method developed in this article is helpful in u nderstanding and predicting the mechanisms of gas evolution in the radiolys is of solid polymers. (C) 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1449-1459, 2001.