Link structure and tribological properties of zinc dialkildithiophosphates

The article considers the dependence of the antiwear and antifriction action dialkyldithiophosphate zinc (ZDDP) from the value of hydrocarbon radicals. Experimentally studied the friction parameters in sliding contact, simulating a radial bearing. The value of the contact pressure, which implements a hydrodynamic modes depends on the roughness of the surfaces. Dedicated mode is boundary lubrication, which differs from the hydrodynamic and boundary friction regimes. This mode is characterized by a relatively constant coefficient of friction and a small amount of wear. As a criterion for evaluation of antiwear properties, used the value of contact pressure at which the transition from the boundary lubrication regime to the regime of boundary friction. It is found that the transition to the boundary friction regime occurs at different contact pressures for the same type of ZDDP with different length of hydrocarbon radicals. When using zinc dihexadecylnaphthalene the transition to boundary friction occurs at much larger values of contact pressure than when using dioctylphthalate zinc. The results are discussed taking into account the mechanism of adsorption of components of lubricating oils on metal surfaces. The dependence of the antiwear action of ZDDP from the length of the hydrocarbon radicals correspond to their influence on the parameters of a multi-molecular adsorption layer. The data on the influence of ancillary components on the structure and mechanical properties of adsorption layers, and on the rheological properties of lubricants in friction units. It is shown that the introduction of a hydrocarbon base oil ZDDP along with other components consisting of linear molecules with a sufficiently long hydrocarbon radicals, affects the range of contact pressures, which implements a hydrodynamic mode of friction. As an example, used hexadecanol diester and maleic acid. The inclusion of such components in the lubricating oil contributes to the implementation of the hydrodynamic regime, but does not affect the transition from boundary lubrication to boundary friction.