Kinetic study of the γ radiolysis of polyethylene

A kinetic study was made of the formation of hydrogen and trans‐vinylene unsaturation in the radiolysis of polyethylene induced by γ rays with a dose rate of 6.35 × 105 rad/hr at 30–100°C in vacuo. The rates of the formation of hydrogen and trans‐vinylene unsaturation were described by the zero‐order formation kinetics with respect to each concentration combined with the first‐order disappearance. The apparent rate constant for the formation of hydrogen increased gradually with rising irradiation temperature to give the activation energy of 0.6 kcal/mole. On the other hand, those for the disappearance of hydrogen and the formation and disappearance of trans‐vinylene unsaturation were almost independent of temperature. The G values for crosslinking and main‐chain scission were obtained from the gel data by using the Charlesby‐Pinner equation, and the activation energy of 1.5 kcal/mole was given for both of them. On the basis of these results the reactions induced by γ rays in solid polyethylene were discussed.