The effects of electron radiation on the properties of ziegler polyethylenes

An investigation has been made of the effects of electron radiation on the properties of stabilized Ziegler polyethylenes. Radiation was applied at dose levels of 0, 2, 5, 10, 25, 50, and 75 Mrad to polymers of various molecular weights and densities. The properties most affected were flow behavior and stress‐cracking resistance. Radiation reduces the melt index of the polymers rapidly and no flow is observed at doses of 10 Mrad or more. A corresponding increase in environmental stress‐cracking resistance is evident and in every case this property reaches a value of 2000 hr. at a dose of 10 Mrad. Changes in other properties are not very great until the radiation dose becomes large. At a dose of 50 Mrad, softening point is increased on the average by 7°C., yield strength is increased on the average by 140 psi, elongation is reduced to a common value of about 200% and impact strength is increased to a common value of about 20 ft. lb./in. notch. Power factor rises to a maximum as the dose is increased to 10 Mrad and diminishes at larger doses. Flex resistance, in the one case examined, diminishes as radiation dose is increased.