Use of high pressure liquid chromatography in the study of liquid lubricant oxidation

The general principles of classical liquid chromatography and high-pressure liquid chromatography (HPLC) are reviewed, and their advantages and disadvantages are compared. Several chromatographic techniques are reviewed, and the analysis of a C-ether liquid lubricant by each technique is illustrated. An analysis by size exclusion chromatography of an ester lubricant, which had been degraded using a micro-oxidation apparatus, is illustrated to show how HPLC can be used in the study of high-temperature lubricant degradation

Formation of high molecular weight products from benzene during boundary lubrication

High molecular weight products were detected on the wear track of an iron disk at the end of a sliding friction and wear test using benzene as a lubricant. Size exclusion chromagography in conjunction with UV analysis gave evidence that the high molecular weight products are polyphenyl ether type substances. Organic electrochemistry was used to elucidate the possible surface reaction mechanisms

Simulation of lubricating behavior of a thioether liquid lubricant by an electrochemical method

An electrochemical cell was constructed to explore the possible radical anion forming behavior of a thioether liquid lubricant. The electrochemical behavior of the thioether was compared with the electrochemical behavior of biphenyl, which is known to form radical anions. Under controlled conditions biphenyl undergoes a reversible reaction to a radical anion, whereas the thioether undergoes an irreversible reduction yielding several products. These results are discussed in relation to boundary lubrication

Preliminary results of the comparison of the electrochemical behavior of a thioether and biphenyl

An electrochemical cell was constructed to explore the feasibility of using electrochemical techniques to simulate the tribochemistry of various substances. The electrochemical cell was used to study and compare the behavior of a thioether 1,3-bis(phenylthio) benzene and biphenyl. It is found that under controlled conditions biphenyl undergoes a reversible reduction to a radical anion whereas the thioether undergoes an irreversible reduction yielding several products. The results are discussed in relationship to boundary lubrication

Analysis of a MIL-L-27502 lubricant from a gas-turbine engine test by size-exclusion chromatography

Size exclusion chromatography was used to determine the chemical degradation of MIL-L-27502 oil samples from a gas turbine engine test run at a bulk oil temperature of 216 C. Results revealed a progressive loss of primary ester and additive depletion and the formation of higher molecular weight products with time. The high molecular weight products absorbed strongly in the ultraviolet indicating the presence of chromophoric groups

Thermal and oxidative degradation studies of formulated C-ethers by gel-permeation chromatography

Gel-permeation chromatography was used to analyze C-ether lubricant formulations from high-temperature bearing tests and from micro-oxidation tests. Three mu-styragel columns (one 500 and two 100 A) and a tetrahydrofuran mobile phase were found to adequately separate the C-ether degradation products. The micro-oxidation tests yielded degradation results qualitatively similar to those observed from the bearing tests. Micro-oxidation tests conducted in air yielded more degradation than did tests in nitrogen. No great differences were observed between the thermal-oxidative stabilities of the two C-ether formulations or between the catalytic degradation activities of silver and M-50 steel. C-ether formulation I did yield more degradation than did formulation II in 111- and 25-hour bearing tests, respectively

A preliminary study of ester oxidation on an aluminum surface using chemiluminescence

The oxidation characteristics of a pure ester (trimethyolpropane triheptanoate) were studied by using a chemiluminescence technique. Tests were run in a thin-film micro-oxidation apparatus with an aluminum alloy catalyst. Conditions included a pure oxygen atmosphere and a temperature range of 176 to 206 C. Results indicated that oxidation of the ester (containing 10 to the minus 3 power M diphenylanthracene as an intensifier) was accompanied by emission of light. The maximum intensity of light emission (I sub max) was a function of the amount of ester, the concentration of intensifier, and the test temperature. The induction period or the time to reach one-half of maximum intensity (t sub 1/2) was an inverse function of test temperature. Decreases in light emission at the later stages of a test were caused by depletion of the intensifier

Analysis of a spacecraft instrument ball bearing assembly lubricated by a perfluoroalkylether

An analysis of a spacecraft instrument ball bearing assembly, subjected to a scanning life test, was performed to determine the possible case of rotational problems involving these units aboard several satellites. The analysis indicated an ineffective transfer of a fluorinated liquid lubricant from a phenolic retainer to the bearing balls. Part of the analysis led to a novel HPLC separation method employing a fluorinated mobile phase in conjunction with silica based size exclusion columns

Analysis of a thioether lubricant by infrared Fourier microemission spectrophotometry

An infrared Fourier microemission spectrophotometer is used to obtain spectra (wavenumber range, 630 to 1230 0.1 cm) from microgram quantities of thioether lubricant samples deposited on aluminum foil. Infrared bands in the spectra are reproducible and could be identified as originating from aromatic species (1,3-disubstituted benzenes). Spectra from all samples (neat and formulated, used and unused) are very similar. Additives (an acid and a phosphinate) present in low concentration (0.10 percent) in the formulated fluid are not detected. This instrument appears to be a viable tool in helping to identify lubricant components separated by liquid chromatography