The effect of space irradiation on the lubricating performance of perfluoropolyether greases in simulated space environment

Abstract

In this paper, 2 kinds of commercial perfluoropolyether (PFPE) greases were coated on the polyimide (PI) blocks, which were placed within simulated space environment including atomic oxygen (AO), proton (Pr), ultraviolet (UV), and electron (El) irradiations, and then the tribological performance has been investigated with a ball‐on‐disc tribometer. Results indicated that the MoS2‐grease showed better lubrication performance than the PTFE‐grease. The changes in infrared spectroscopy induced by Pr and El irradiations were more obvious than that by AO and UV irradiations. Results of energy dispersive X‐ray spectroscopy indicated that Pr and El irradiations caused carbonation of greases, and AO and UV irradiations induced oxidation of greases. Referred to the tribological properties of PI coated with PFPE oil, PI coated with PFPE greases showed minor changes in friction coefficient and wear rate, and the MoS2 additives could significantly improve the lubrication properties of PFPE greases in simulated space environment.

Tribological properties of the polyacrylate/PTFE coating modified by POSS in the space environment

“…The peaks for the OvPOSS/PMB/PTFE coatings [Figure (b)] show a similar trend with the pristine coating after UV and EI exposition. On the contrary, the characteristic peaks at 2956 cm −1 (CH 3 ) and 1716 cm −1 (C  O) were greatly weakened after AO exposure, whereas the peaks for the CF and SiO bonds only slightly changed, which indicates that the AO induced a complex chemical process in the coatings . Most likely, the irradiation resulted in the fragmentation of the macromolecule chains by breaking CC, CO, and CC bonds, which destroyed the microstructure and the composition of the coating as the organic bonds were oxidized into volatile by‐products and escaped from the surface …”

Tribological performance of IL/(GO-MWCNT) coatings in high-vacuum and irradiation environments

“…The Pr and El irradiation times were controlled at approximately 10 and 120 min, respectively, because the Pr and El irradiations had higher energy than the AO and UV irradiations. The speed of a spacecraft in outer space is approximately 7 to 8 km/s, and this relative velocity endowed the particles with a flux about 10 12 –10 15 atoms cm 2 s −1 28 , 29 . Therefore, in our irradiation device, the flux of Pr, AO, and El irradiation was close to that of AO produced by electron cyclotron resonance microwave plasma technology and had mean kinetic energy of 5 eV, which is similar to the energy of AO impinging on the surface of a spacecraft in a space environment 30 .…”

Diversity of Synthetic Approaches to Functionalized Perfluoropolyalkylether Polymers

“…14 This highlights the usefulness of the chemical modification of PFPAEs for lubricant applications as well as in confined spaces even in a simulated space environment. 15 However, even though their lubricant characteristics are their major advantage, high-performance thermoplastics and thermosets were fabricated after their chemical modification. Because of the intrinsic properties of the fluorine atoms, omniphobic coatings were obtained through a thermal process such as sol−gel procedures 16−19 or photochemical processes with (meth)acrylate substituents.…”

“…On the other hand, functionalized PFPAEs having four hydroxyl, cyclotriphosphazene, piperonyl, or even 3-phenylpropyl groups were examined depending on their adhesion, mobility, or humidity resistance properties and also compared to nonfunctionalized PFPAEs. − Molecular dynamic simulations were often applied to determine the lubricity properties , as for silane-terminated PFPAE films to investigate the intrachain and interchain interactions in view of antifingerprint coatings . This highlights the usefulness of the chemical modification of PFPAEs for lubricant applications as well as in confined spaces even in a simulated space environment . However, even though their lubricant characteristics are their major advantage, high-performance thermoplastics and thermosets were fabricated after their chemical modification.…”