Atomic Oxygen-Resistant Epoxy-amines Containing Phenylphosphine Oxide as Low Earth Orbit Stable Polymers

Abstract

Atomic oxygen (AO) attacks carbon-fiber reinforcing polymers on the surfaces of spacecraft in low Earth orbit and threatens safe spacecraft operation and service life. Incorporating phenylphosphine oxide (PPO) groups into polymer chains offers a self-regenerating method of protection from AO but remains poorly understood. Herein, epoxies containing PPO groups were synthesized with increasing concentrations of phosphorus [P] from 0 to 8 wt % to investigate their AO resistance. Thin films of PPO-containing epoxies were exposed to AO via oxygen plasma etching and characterized by interferometry, X-ray photoelectron spectroscopy, and atomic force microscopyinfrared spectroscopy. Measurements confirmed that the exposure of these materials to AO produces a passivation phosphate (PO x ) layer on the surface of the sample, resulting in up to 100X decrease in AO erosion rates. Furthermore, key insights into the relationship between initial [P], passivation layer surface topology, and polymer depth profiles were obtained. Crucially, the results indicate that these materials advantageously did not exhibit linear erosion rates when exposed to AO, in contrast to most organic polymers, and their AO resistance can be readily tuned via synthetic incorporation of monomers with varying [P].

Enabling quantitative analysis of complex polymer blends by infrared nanospectroscopy and isotopic deuteration

“…11,16 For example, Fuchs et al , used AFM-IR to monitor the degradation of a phenylphosphine oxide (PPO)-modified epoxy when exposed to atomic oxygen. 17 After atomic oxygen exposure, samples containing low concentrations of PPO developed microscale nodes on the surface, indicating heterogeneous material decay. In contrast, samples containing higher concentrations of PPO maintained a comparatively homogenous surface.…”

Atomic Oxygen Resistance Vitrimers with High Strength, Recyclability, and Thermal Stability

“…Organic polymers like epoxy resins (EP) are extensively used in spacecraft owing to their light weight, high mechanical strength, excellent thermal stability, and chemical resistance. − However, these organic polymers could be easily degraded when exposed to atomic oxygen (AO), the primary factor for destroying organic polymers at low earth orbit (LEO) altitudes of 200–700 km, leading to the breakage of covalent bonds and molecular chains. , The degradation of these polymer materials will reduce the lifetime and pose great hidden dangers to the normal operation of the spacecraft . To solve this problem, researchers have proposed an effective approach by depositing protective coatings on the surface of polymers, such as silica, metal oxides, polysiloxanes, magnesium alloys, diamond carbon, polyhedral oligomeric silsesquioxane (POSS), − and phenylphosphine oxide. − Among these strategies, POSS with inorganic nanocage has superior durability against thermo-oxidative reactions, and enhancing the AO resistance by adding POSS has been intensively studied. − However, in addition to exposing in the AO erosion environment, the harsh environment with huge temperature differences between day and night is also faced during practical applications, which usually causes cracking of the AO-resistant coatings. Irreversible cracking will obviously destroy the AO-resistant ability of coatings and shorten the service life of spacecraft materials.…”

Preparation and Characterization of Transparent Polyimide Nanocomposite Films with Potential Applications as Spacecraft Antenna Substrates with Low Dielectric Features and Good Sustainability in Atomic-Oxygen Environments

“…When the spacecraft cruised in LEO at the speed of 7.9 km/s, the impact energy between the collision of polymer antennas and the AO species might be as high as 5 eV. This usually causes severe corrosion of the polymer substrates in the antennas due to the dissociation of chemical bonds in the polymers by the high-energy impacts [ 6 , 7 , 8 , 9 , 10 ]. For example, for the common polyimide (PI) substrates derived from pyromellitic anhydride (PMDA) and 4,4′-oxydianline (ODA) (PI PMDA-ODA ), which are most widely used at present in spacecraft antennas, as shown in Figure 1 , the molecular structure is mainly composed of C-N bond (dissociation energy: 3.2 eV), C 6 H 5 -H bond (dissociation energy: 4.8 eV), and -C 6 H 5 -C(=O)- bond (dissociation energy: 3.9 eV) [ 11 ].…”