Low-Energy-Electron-Stimulated Degradation of a Multiply Alkylated Cyclopentane Oil and Implications for Space Bearings

Abstract

The volatile and liquid-phase products of low-energy electron irradiation of a multiply alkylated cyclopentane oil in vacuum were analyzed using mass spectroscopy, infrared spectroscopy, supercritical fluid chromatography, and gel-permeation chromatography. Both alkanes and alkenes are formed in each phase; in the fluid both primary and trans-alkenes are detected. Smaller and larger molecules than are present in the original oil (product molecular weights up to at least 10,000 g/mol) are found, and alkenes are present over the entire molecular weight range. The dependence of the amount of products found on electron beam energy and current suggest that the first step of the process is fragmentation of the oil molecules and their initial transformation into both volatile and non-volatile alkenes and alkanes, followed by further reaction to form larger molecules. Combining these results with an estimate of the properties of the triboelectrons that would probably be produced during wear in either all-steel or hybrid (steel raceways with ceramic balls) ball bearings in spacecraft, we find that degradation in vacuum due to triboelectronic reactions alone, with this type of lubricant in this application, is insignificant. Oil degradation in these systems in vacuum is likely due to chemical reactions with fresh metal surfaces produced during wear.

Tribochemical degradation of vacuum‐stable lubricants: A comparative study between multialkylated cyclopentane and perfluoropolyether in a vacuum ball‐on‐disc and full‐bearing tests

“…The XPS surface analysis revealed an oxidation and fragmentation reaction of the MAC fluid with debris particles and the nascent wear track. The in situ mass spectrometry indicated the formation of various alkanes and alkenes (CH 3 + , C 2 H 3 + , C 2 H 5 + , C 3 H 5 + , and C 3 H 7 + ) with different chain lengths during each loading interval . The test performed using the fluorocarbon‐based PFPE oil showed no correlation between the measured hydrogen partial pressure and tribological contact.…”

Hydrogen assisted rolling contact fatigue due to lubricant degradation and formation of white etching areas

“…As a product of the degradation reaction lubricant fragments like H 2 + , CH 3 + , C 2 H 3 + , C 2 H 4 + , and C 3 H 7 + were formed [20,21,22,23,24,25,26]. Additional oxidation reaction products of the lubricant and the metal oxide layer like esters, ethers, and carboxylic acids were detected [24,27,28,29,30].…”

Highly stable tribological performance and hydrophobicity of porous polyimide material filled with lubricants in a simulated space environment

“…Among them, protons, electrons, atomic oxygen and ultraviolet rays could severely erode the materials used in the spacecra and then induce equipment failure, especially for proton radiation, which causes the worst damage to polymer materials. [6][7][8][9][10][11] Therefore, developing durable materials that can be applied to the extremely rigorous space environment is still a highly challenging task.…”