Tribology of High-Performance Polymers at Extreme Conditions From Cryogenic to Elevated Temperatures
Date
2022-07-25Metadata
Show full item recordAbstract
There is a strong need for long life bearings and tribological surfaces for expanding the ability of NASA and other space companies and agencies to explore the deep atmosphere and surface of different planets and comets using long-lived (days or weeks) balloons and landers. The missions would experience extreme temperatures - ranging from cryogenic temperatures of -220°C on Europa to upwards of 462°C on Venus, which impede the use of traditional oil lubricants and greases, resulting in dry sliding conditions that generally have significant detrimental effects on component performance; with the addition of abrasive dusty environment in Mars, the complexity is further compounded.
To address these challenges, high-performance polymers (HPPs) based on polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), polyimide (PI), and aromatic thermosetting co-polyester (ATSP) were selected for tribological experiments at extreme temperatures ranging from -196 to 300°C, simulating extreme operating conditions that bearing materials in space will encounter. The efficacy of adding solid lubricants such as PTFE, graphene nanoplatelets (GNPs), and graphite to ATSP polymer matrix was studied, and the best lubricant composition was selected. The addition of GNPs and PTFE was shown to significantly decrease the friction and improve the wear resistance of the polymer composite, compared to neat ATSP. The developed transfer film and its characteristics were found to substantially affect the tribological performance. Inspired by the beneficial effects of this “transfer layer,” a novel method was proposed to deposit the polymer coating on both pin and disks to simulate polymer coating sliding on pre-deposited “transfer layer.”
ATSP polymer composite was shown to outperform the other groups of HPPs with low coefficient of friction and unmeasurable “zero” wear from cryogenic to high temperatures (-196°C to 300°C) under dry sliding conditions, expanding the application of the polymer to 500°C temperature range. In addition, polymer-on-polymer sliding significantly mitigated the sand and dust accumulation at the interface, which is advantageous for Lunar/Mars explorations. The work contributes to the current and future research on the development of HPPs for space exploration devices and other engineering applications that require operation under extreme environments.
Citation
Bashandeh Khodaeinaeini, Kian (2022). Tribology of High-Performance Polymers at Extreme Conditions From Cryogenic to Elevated Temperatures. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /197977.