Effect of nanoparticles and siloxane groups on the atomic oxygen erosion resistance of copolyimides

The properties, resistance to atomic oxygen (AO) in particular, of copolyimides based on 4,4′-(9-fluorenylidene)dianiline, 3,3′,4,4′-diphenyloxide tetracarboxylic acid and hexamethylenediamine (PI-1), 4,4′-(9-fluorenylidene)dianiline, 3,3′,4,4′-tetracarboxylic acid diphenyloxide and 1,3-Bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (PI-2) were studied. Tris-(methyldiethoxysiloxy)gallium and tetrakis-(methyldiethoxysiloxy)hafnium were used as precursors for in situ filling of the polymers. The filling of copolyimides leads to an order of magnitude decrease in the specific mass loss of nanocomposites under the AO action. The filled PI-2 shows the better resistance to AO compared to the PI-1 nanocomposite. Based on the analysis of the erosion rates of polymer films, it was shown for the first time that at low fluences the resistance of filled PI-2 to atomic oxygen erosion is determined by the filler, whereas at high fluences the protective function is based on both components of the nanocomposite (filler and matrix). In the case of nanocomposites based on siloxane-free PI-1, their resistance to atomic oxygen erosion is caused by the nanoparticles, regardless of the fluence value.