Atomic oxygen resistance of polyimide/silicon hybrid thin films with different compositions and architectures

Abstract

Silicon (Si)-containing polyimides (PIs) with superior atomic oxygen (AO) resistance are promising materials for space applications. Here, in this study, we present the synthesis and characterization of eight Si-containing PI thin films and evaluate their AO durability. The resulting PI films exhibited high thermal stability and preferable AO resistance but showed slightly reduced mechanical performance relative to pristine PI. The highest optical transparency at 550 nm was observed for PI/octaaminopropylsilsesquioxane, while the lowest value was observed for PI/silica (SiO2) hybrids. X-Ray photoelectron spectroscopic study suggested that the topmost surface of PI was degraded at the early stage and an SiO2 inert protective layer was finally formed on the surface of hybrid films after AO exposure. It is found that Si-containing units of higher oxidation states and with higher Si/O molar ratio are favorable to improve the AO resistance. Dispersion of Si at molecular level contributes to improving anti-AO property as well as optical transparency of the prepared films. The characterization of scanning electron microscopy indicated a continuous SiO2 protective layer was crucial to prevent AO from eroding the bulk matrix.

Evolution of surface chemistry and morphology of hyperbranched polysiloxane polyimides in simulated atomic oxygen environment

“…It is significant to note that, O/Si ratio of PI -21.9 and PI -29.7 rapidly reaches approximately 2/1 albeit undergoing a small dose of AO irradiation of 0.88 × 10 20 O atoms cm −2 . This implies a rapid conversion of silsesquioxane to SiO 2 upon AO exposure [4,23], which is well consistent with remarkable decrease in surface carbon atomic concentration as is graphed in Fig. 7a.…”

“…Therefore, a much denser and more connected silica passivating layer is likely to play a more positive role in resisting AO attack. In fact, during the initial stages of degradation of a HBPSi polyimide, erosion of the organic portions occurs and will compete with the development of a SiO 2 passivating layer [4,18,23]. When HBPSi loading is not particularly high, such as 4.1 wt%, polyimide erosion may be significant and makes a dominant contribution to mass loss.…”

“…1. The specific operation procedures and details of the system were described in our previous study [18,23]. The AO flux at the sample's position was finally calculated to be approximately 4.89 × 10 15 atom cm −2 s −1 from mass loss of Kapton ® H. During AO exposure, all samples were handled in vacuum chamber and irradiated to various AO fluences ranging from 0.88 to 3.87 × 10 20 O atoms cm −2 or larger for some select samples.…”

“…Amine-functionalized HBPSi was synthesized according to our previous study [18,23]. Typically, to a 100 mL, round-bottom flask containing 25 g of THF was added 0.01 mol of TEOS, 0.07 mol of DPDMS and 6.5 mmol of APS.…”

A comparative study of characteristics of polytetrafluoroethylene fibers manufactured by various processes

“…Environmental scanning electron microscopy (SEM) (Quanta250, FEI Czekh) was employed to analyze morphologies of PTFE fibers. Samples of filaments or fibers were sputtered with a thin layer of Au to avoid charging, and then imaged using the SEM at 3.5 KV acceleration voltage …”