Effects of Vacuum Ultraviolet Radiation on DC93-500 Silicone

Vacuum ultraviolet radiation is among the space environment elements that can be hazardous to DC93-500 silicone film, which has been proposed for use on spacecraft exterior surfaces. Investigations have been conducted to examine vacuum ultraviolet effects on DC93-500 film. Laboratory exposure tests were used to determine the effectiveness of various wavelength ranges in causing optical and mechanical degradation and to determine intensity-dependence of optical and mechanical properties degradation. Results indicated that wavelengths between 185 and 200 nm were significantly more effective in causing degradation than wavelengths between 140 and 185 nm. These findings were consistent with results of vacuum ultraviolet ellipsometric optical measurements, which provided data on depth of penetration in DC93-500 as a function of wavelength. Wavelengths between 185 and 200 urn penetrate to depths between 1 and 3 zm in DC93-500, depths where bulk degradation is likely, whereas the penetration of shorter wavelengths is much more shallow and more likely to result in only surface degradation. Results of exposures of DC93-500 film samples to vacuum ultraviolet radiation of intensities between 1.5 and 5.5 times the sun's intensity indicated no intensity-dependence of optical and mechanical property degradation.