Investigation of the protective ultraviolet absorbers in a space environment. III. Protective effectiveness

The effectiveness of the ultraviolet absorbers in protecting organic coatings exposed to an extraterrestrial environment from photochemical degradation was studied for the commercially available absorbers and certain errocene derivatives. The change in solar absorptivity of the coatings was used as a measure of the degradation incurred, these data being obtained from the ultraviolet, visible, and near-infrared absorption spectra of the polymers. Ultraviolet absorbers of the benzophenone and benzotriazole type used for terrestrial applications were found to be considerably less effective in a space environment. This was attributed to the strong ultraviolet absorption of the polymers at the shorter wavelengths, which competes with the absorber for the incident radiation. Certain benzoyl-substituted ferrocene compounds were found to be extremely effective in protecting many types of polymeric coatings. The benzoylferrocenes are highly colored materials (red to orange) whose absorbing properties are extremely stable to ultraviolet radiation.