12-HSA/PAO10 Supramolecular Gel Lubricants Preparation and Tribological Properties Investigation

Abstract

Traditional lubrication methods face challenges related to spatial constraints and suboptimal tribological performance in high-speed small-module gears. To address these limitations, this study prepared supramolecular gel lubricants using three gelators—12-hydroxystearic acid (12-HSA), glycerol monostearate (GMS) and salicylic acid (SA), reacting with two base oils (PAO10 and 500SN). The gelation mechanisms, thermodynamic stability, rheological behaviour, and frictional properties were elucidated by integrating molecular dynamics (MD) simulations, Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), rheological measurements and four-ball tribological tests. The results indicated that 12-HSA exhibited the strongest gelation ability. The hydroxyl group (OH) and carboxyl group (COOH) in its molecule can form primary coordination clusters through ‘OH⋯O’ oriented hydrogen bonds, thereby constructing a three-dimensional crosslinked network to achieve the curing of the low-polarity, low-molecular-weight PAO10 matrix. The stable gelation was achieved at 1 wt.% and demonstrated an ultralow critical gelation concentration. With the increase of 12-HSA, the gel melting peak temperature shifted from 120°C to 135°C, and creep–recovery tests showed a marked increase in shear recovery rate, indicating that strengthened intermolecular interactions were the key drivers for enhanced network crosslinking strength and thermal stability. The tribological performance of the supramolecular gel was optimal at 5 wt.% 12-HSA, in which the friction coefficient decreased by 22.0%, and wear scar diameter and wear scar volume were reduced by 11.8% and 11.6%, respectively, owing to the formation of a stable boundary film through synergistic lubrication. This study provides an efficient adaptive lubrication solution for high-speed small-module gears and offers valuable insights into the design of supramolecular gel lubricants.