Edward R. Long

Mechanism of electrical conductivity in an irradiated polyimide

Abstract A polyimide was exposed to 1.0 MeV electron radiation. The radiation-induced radical density and d.c. conductivity were measured at various post-irradiation times. The radiation-induced radical density was found to be correlated to the increased d.c. conductivity through a hopping model of conductivity. The post-irradiation radical species were identified.

Electron-Radiation Effects on the AC and DC Electrical Properties and Unpaired Electron Densities of Three Aerospace Polymers

The effects of gigarad-level total absorbed doses from 1-MeV electrons on the post-irradiation alternating-current (ac) and direct-current (dc) electrical properties and the unpaired electron densities have been studied for Kapton,® Ultem,® and Mylar.® The unpaired electron densities (determined from electron paramagnetic resonance spectroscopy) and the dc electrical conductivities of the irradiated materials were monitored as functions of time following the exposures to determine their decay characteristics at room temperature. The elevated-temperature ac electrical dissipations of the Ultem and Mylar were affected by the radiation. The dc conductivity of the Kapton increased by five orders of magnitude, while the dc conductivities of the Ultem and Mylar increased by less than an order of magnitude, due to the radiation. The observed radiation-generated changes in the ac electrical dissipations are explained in terms of known radiation-generated changes in the molecular structures of the three materials. A preliminary model relating the dc electrical conductivity and the unpaired electron density in the Kapton is proposed.

Effects of Intermediate-Energy Electrons on Mechanical and Molecular Properties of a Polyetherimide

An experiment, using 100-keV electrons and 109-rad doses, was conducted on Ultem* polyetherimide film. Mechanical, electron paramagnetic resonance, and infrared spectroscopic data suggested that the radiation produced crosslinking and embrittlement of the material.