水和羧酸钙对润滑油氧化产物聚集影响的分子动力学

采用分子动力学(MD)模拟的方法，研究了不同温度下润滑油氧化产生的极性小分子的聚集行为以及水和羧酸钙分子对其聚集的影响。研究结果表明：润滑油氧化产物分子可以通过氢键产生聚集，形成的氢键聚集体相互作用能为14~58 kJ/mol;随着温度的升高,键能较低的氢键不易形成或容易断裂，因此其聚集程度降低；当体系中含有水或羧酸钙分子时，不同温度下均发生明显的聚集，分别形成了润滑油氧化产物包裹的水分子团聚体或羧酸钙分子的聚集体。润滑油氧化产物与水和羧酸钙分子之间的相互作用能分别为24~60 kJ/mol和66~87 kJ/mol，其比各类润滑油氧化产物分子之间形成的氢键聚集体的相互作用能高，稳定性更好，因此可以在温度较高的条件下形成较稳定的聚集体。

Molecular Dynamics Simulation on the Effect of Water and Carboxylic Acid Calcium on the Aggregation of Lubricant Oxidation Products

Molecular dynamics (MD) simulations method was used to study the aggregation of molecules of lubricant oxidation products and the effect of water and carboxylic acid calcium on the aggregation. Simulation results suggest that aggregates can be formed between molecules of lubricant oxidation products by hydrogen bonds. The interaction energy of hydrogen bonds formed by different lubricant oxidation product molecules is between 14 kJ/mol to 58 kJ/mol. The degree of aggregation reduces with the increase of temperature because hydrogen bonds with low interaction energy is easy to rupture or difficult to form at higher temperatures. Severe aggregations can take place under different temperatures when lubricants contain water molecules or carboxylic acid calcium molecules, and lead to the formation of water molecule aggregates or carboxylic acid calcium molecule surrounded by lubricant oxidation product molecules, respectively. The interaction energy between water molecule and lubricant oxidation product molecules can be 24 kJ/mol to 60 kJ/mol, and the interaction energy between carboxylic acid calcium molecule and lubricant oxidation product molecules is from 66 kJ/mol to 87 kJ/mol. Both of the above interaction energies are higher than that among lubricant oxidation product molecules. Aggregates formed in the former are more stable, and thus lead to obvious aggregation occurs at higher temperatures with presence of water or carboxylic acid calcium in lubricants.