| Popis: |
The study of the resistance of various thermo-regulating (thermal control) protective coatings to space environment was conducted on carbon fiber-reinforced polymer (CFRP) epoxy composites and three-layered honeycomb specimens after the longterm exposure of “Komplast” removable cassettes outside of “Kvant-2” module of Space Station “MIR”. Scanning electron microscopy (SEM), X-ray spectral analysis and visual inspection were used as the major tools in the study. Surfaces of white thermal control coatings, based on acrylic and epoxy polymers, in pristine condition and after 839 and 1218 days of the exposure were comparatively evaluated. In addition, similar analysis was conducted for a number of coatings based on organosilicone polymers, for inorganic coatings based on liquid glass, and aluminum foil, after 1024 days of space exposure. During the space exposures, some specimens with coatings of similar types were exposed in holders allowing to keep them in a stack, one under another with positioning of the upper specimen with the coating on outside and of the lower specimen’s coating facing the wall of the module that allowed to expose coatings of the same structure to different space conditions. Different types of macro- and micro-defects that appeared in the coatings were revealed, in particular, long cracks with a partial delamination of the coating from the substrate, a network of thin web-like cracks, scaly swelling-up and ring-like delamination. The change of the coatings surface composition, including the substances deposited on the surface during the long-term exposure in space, was evaluated. The possible coatings degradation mechanisms under the complicated space environment factors were discussed, with the account for the coating’s chemical nature. |
