THE MASS-LOSS MECHANISMS OF POLYMERS IN A RADIO-FREQUENCY INDUCED ATOMIC OXYGEN ENVIRONMENT

The effects of atomic oxygen on several classes of polymers were inves tigated. Particular attention was directed to the determination of ero sion or mass loss mechanisms in relation to the physical and chemical structures of polymers. Nineteen polymeric materials were exposed to a thermal atomic oxygen environment at fluxes of 10(22) atoms/m2-sec. B ulk material temperatures were maintained at 10, 45, and 75-degrees-C during exposure. Mass loss rate, which was characteristic of the type of polymer, was proportional to the exposure area and was linear in ti me for most polymers except for Mylar, which produced a shielding high temperature ash. The mass loss rate for the atomic oxygen degradation of polymers was related to the bond strength of the polymer structure and to the shielding effect of pendant structures. This degradation p rocess was strongly dependent on polymer temperature. Activation energ ies ranged from 1 to 48 KJ/mole and were found to be related to gaseou s diffusion in polymers. Frequency factors were proportional to activa tion energies. Activation energies were found to increase with increas ed mol wt and crosslinking. An equation was developed relating exposur e area, atomic oxygen flux, frequency factor, and activation energy to the rate of polymer mass loss.