Stabilisation of hydrogen bonding in polypropylene glycol at EHL contact region

Abstract

In the present work, the stabilisation of hydrogen bonding of polypropylene glycol at elastohydrodynamic lubrication (EHL) contact was investigated by in situ observation with a micro-Fourier transform infrared spectrometer, and the effect of hydrostatic pressure on infrared (IR) spectra was confi rmed using a diamond anvil cell. Polypropylene glycols with different molecular weights were used as sample oils. Polypropylene glycol molecules interact with themselves by hydrogen bonding with their hydroxyl groups. Stability of the hydrogen bonding is observed by IR peak shift of the O-H stretching mode (3400-3700 cm −1 ). In the case of the dynamic condition under EHL, the C-H stretching mode shifted to a higher wavenumber, whereas the O-H stretching mode shifted to a lower wavenumber at the Hertzian contact region. This result means that the hydrogen bonding of polypropylene glycol was stabilised under high pressure, and the stabilisation of hydrogen bonding by pressure was dependent on the molecular weight of polypropylene glycol.

Effect of pressure and temperature on the molecular interaction of polar lubricant containing oleic acid in polypropylene glycol observed by infrared spectroscopy

“…This result demonstrates the pressure and temperature response of the hydrogen bonding of lubricant molecules, which suggests change of molecular interaction. In past study, it was found that the peak position of the O–H stretching mode in PPG and the C═O stretching mode in OA were shifted to a lower wavenumber at the Hertzian contact region …”

“…The O–H stretching mode at 3480 cm −1 and the C═O stretching mode at 1735 cm −1 are related to the associated structure formed by hydrogen bonding . The O–H stretching mode of base oil shows the interaction between OH groups . The C═O stretching mode of OA consists of two peaks, the major peak at 1735 cm −1 as a monomer interacted with base oil and the minor peak at 1712 cm −1 as a dimmer interacting with itself, respectively .…”

“…We have investigated that molecular interaction between molecules of additive and base oil at EHL contact by means of in situ observation with micro‐Fourier Transform IR Spectrometer (micro‐FTIR) . It was found that hydrogen bonding of lubricant molecules was stabilised by high pressure of the Hertzian contact region.…”

<i>In Situ</i> Observation of Lubricant Film of Semi-Solid Lubricants at EHL Contact Using Micro-FTIR

“…Micro-Fourier transform infrared spectrometry (micro-FTIR) is useful for the in situ observation of a lubricant film under elastohydrodynamic lubrication (EHL) conditions. In previous studies, several tribological phenomena at the contact point were investigated, such as the change in concentration of components [2], molecular orientation [3], and molecular interactions [4]. The results demonstrated that tribological performance was closely related to the structure of the lubricant film at the contact point.…”

Effects of Surface Chemical Properties on the Frictional Properties of Self-Assembled Monolayers Lubricated with Oleic Acid

“…Infrared (IR) absorption spectroscopy [2][3][4][5][6][7][8][9][10][11][12][13][14][15] and Raman spectroscopy [16][17][18] are particularly attractive tools for studying buried interfaces nondestructively. There are many practical and interpretational problems associated with the application of Raman and IR spectroscopy to in-contact studies.…”