Pressure dependence of free radical decay in irradiated isotactic polypropylene

Free radicals were generated in isotactic polypropylene by gamma-irradiation. The samples were annealed at pressures between 1 and 8000 atm and temperatures between 60 and 110°. The concentration of free radicals was estimated by the ESR method. The rate constants of free radical decay were determined for various pressures and temperatures. The rate constant of free radical decay decreases with increasing pressure while the activation energy increases. The relationship between the kinetics of molecular motion and the kinetics of free radical decay is discussed.