Electron-Induced Conduction in Plastics. II. Bulk Excitation in Polystyrene and Other Insulating Polymers

Abstract

The electrical conduction in a number of commercial plastics has been studied under pulsed bombardment by fully penetrating electrons. Detailed results are given mainly for polystyrene. The kinetics obeyed by the ``prompt'' component of the induced current are predominantly first order, those of the ``long‐lived'' current, second order. The results generally support the assumptions made in Paper I, and in particular confirm the interpretation of the decay time of the long‐lived current as a bimolecular recombination lifetime. A simple model for radiation‐induced conduction in polymers, based on topological considerations, is developed. The prompt component is identified with intramolecular carrier drift. The mobility in this process has a lower limit of 10⁻² cm²/Vsec. The long‐lived current is associated with intermolecular jumps. It is suggested that, while the effective mobility of the long‐lived component (as determined in Paper I) in kinked‐chain polymers is controlled by the intermolecular jump probability, that in polyethylene is subject to an additional limitation, viz. strong localization of carriers in the U bends of the molecules.