Duo armour for harsh space environment: Development of polyimide nanocomposites for atomic oxygen endurance and electrostatic dissipation

Aggressive space-environment offers high atomic-oxygen (ATOX) concentration and static-charge accumulation on pristine-polyimide resulting in chemical degradation. Herein, we report the development of unary/binary/ternary nano-reinforced polyimide-films by in-situ step-growth polymerization to evaluate their performance in simulated LEO/VLEO space-conditions for ATOX-endurance and electrostatic-dissipation. The nano-reinforcements developed in this study are polyaniline-grafted-sepiolite polymer-brushes(P3%PB) prepared by emulsion-graft polymerization, gold-nanoparticles-embedded-sepiolite(Au-ES) and graphene which are reinforced for the first-time in polyimide-matrix. The developed nanocomposites were characterized by UV-Visible, DLS and FTIR-spectroscopy along with XRD, SEM-EDX to assess structural composition, particle size, crystallinity, surface morphology and elemental composition. TGA demonstrated remarkable thermal stability of polyimide nanocomposite films. The surface-resistivity of the ternary-nanocomposite was significantly reduced to 2.16×10⁶Ω/sq proving them to be electrostatic-dissipative materials. Ground-based simulated ATOX-tests revealed superior performance for binary(P2%Au1%) and ternary(P2%G1%Au1%) nanocomposites, exhibiting a mass-loss of only 20.25% and 22.76% respectively compared to pristine-polyimide which displayed the mass-loss of 76.06% at the fluence of 8.0×10 20 atoms/cm 2 . The before and after ATOX-exposure results are also supported by AFM-topographical-analysis. This study offers an innovative approach for the fabrication of polyimide-films for dual-performance (ATOX-resistant and electrostatic-dissipative PI) to enable the LEO/VLEO spacecrafts to complete highly integrated flight missions more effectively and displays high potential in the development of nano-reinforcement-polymer interface. • Unary, binary and ternary polyimide films were synthesized by in-situ step-growth polymerization process • Three nano-reinforcements are polyaniline grafted sepiolite polymer brushes, gold nanoparticles embedded sepiolite and graphene flakes • Pristine PI and its nanocomposite films were tested for ground-based simulated atomic oxygen exposure experiments to analyse their endurance against atomic oxygen attack and their surface resistivity was analysed for electrostatic dissipation • Ternary nanocomposite film (P2%G1%Au1%) has displayed excellent ATOX resistance by losing only 22.76% mass at the fluence of 8.0×10 20 atoms/cm 2 and exhibited surface resistivity of 2.16×10⁶Ω/sq proving the films to be promising candidate for LEO/VLEO harsh space environment