Friction and Wear Protection Performance of Synthetic Siloxane Lubricants

Several new siloxane lubricants were synthesized with linear and ring-shaped branch structures of various lengths and branch contents, aiming at a search for better molecular design for lower boundary friction and more effective surface protection against wear of materials. Their molecular structure and mass were measured by means of nuclear magnetic resonance and gel permeation chromatography, respectively. The new lubricants were compared with commercially available polysiloxanes, poly-α-olefins, and perfluoropolyether in lubricating a steel ball-on-steel disk interface using a tribotester at a load of 1.76 GPa and an entrainment speed of 0.025 m/s. The results are used to explain the effects of alkyl branch length L , pendant type J , percent of branch functional monomers Q , and degree of polymerization DP on siloxane design for the most effective boundary lubrication.