Tribological properties of polyol-ester-based lubricants and their influence on oxidation stability

Abstract

Unlike oxidative degradation of lubricants, tribology-induced degradation is rarely studied. In this work, the tribological performance and oxidative stability of ester-based lubricants were evaluated before and after tribological testing. Results showed that the tribological performances of base oils are highly dependent on the lubricant formulation and test conditions. Tribological processes could cause detrimental effects on oxidative stability even under moderate conditions. The addition of antiwear additives seems to effectively inhibit the chemically breakdown of esters by forming a protective film. Mechanical shearing, high temperature in contact zones, catalytic effect of nascent surface, wear debris, as well as self- catalysis are the major reasons that are responsible for the oxidative deterioration of the lubricant after tribological testing.

Vegetable Oil-Based Pentaerythritol Ester for Industrial Air Compressor Applications: A Tribological Investigation

“…A robust film with a high viscosity is formed in part by the free fatty acids (from the vegetable oils) [26]. Even at high loads and high sliding velocity, this film separates and avoids the metal-to-metal contacting surfaces between the pin and disc [27,28].…”

Preparation and performance evaluation of an ester‐bridged antioxidant used as multifunctional additive in ester oil

“…Owing to their excellent properties such as high thermal-oxidative stability, low-temperature fluidity, outstanding viscosity-temperature performance and lubricating properties, synthetic esters have attracted considerable interest. [1][2][3][4] However, with the rapid advancement of equipment, synthetic ester oils fail to satisfy operations demand under increasingly harsh working conditions, especially the high temperature of the lubrication system. 5,6 The high-temperature status inevitably caused rapid thermal oxidation of the synthetic ester oils to form some degradation products and/or polymerised large molecules; consequently, the harmful substances deteriorate their comprehensive performance, resulting in a short service life of the lubricants.…”

“…Synthetic esters are classified as API Group V base stocks and have been widely used in many applications such as automobile and aviation engine oils, compressor oils, and gear oils. Owing to their excellent properties such as high thermal‐oxidative stability, low‐temperature fluidity, outstanding viscosity–temperature performance and lubricating properties, synthetic esters have attracted considerable interest 1–4 . However, with the rapid advancement of equipment, synthetic ester oils fail to satisfy operations demand under increasingly harsh working conditions, especially the high temperature of the lubrication system 5,6 .…”