Enhanced Extreme-Pressure and Antiwear Performance of Organically Modified Synthetic Montmorillonite/ZDDP Composite Additives

Synthetic montmorillonite (MMT) was prepared via a hydrothermal method and further modified through organic intercalation to obtain organically modified montmorillonite (OMMT). Using OMMT as an oil additive, four-ball tribological tests showed that both alkyl chain length and intercalation level play critical roles in lubrication performance, with longer chains and higher organic loadings resulting in improved friction-reduction and antiwear properties. Under high-load and long-duration conditions, the synthetic OMMT/ZDDP composite additive exhibited excellent lubrication stability and antiwear capability, significantly outperforming naturally derived organically modified montmorillonite NOMMT/ZDDP oil. The enhanced performance was attributed to the formation of a stable composite tribofilm, which combines the load-bearing capacity of the inorganic layered structure with the self-repairing capability of the tribochemical reaction film. Modified synthetic montmorillonite provides a uniform interlayer structure for the development of a stable, synergistic lubricating protective film.