不同交联密度下硫化丁腈橡胶摩擦特性的分子动力学模拟

Molecular Dynamic Simulation of Tribological Properties of Vulcanized Nitrile Rubber with Different Crosslinking Densities

建立了不同交联密度(0.4,0.8,1.2,1.6)硫化丁腈橡胶-铁基板分子动力学摩擦模型,分析了在剪切摩擦过程中交联密度对摩擦因数、相对原子浓度、摩擦界面温度和橡胶分子均方位移的影响,并对模型的准确性进行了试验验证。结果表明:硫化丁腈橡胶-铁基板摩擦副的摩擦因数随交联密度的增加而增大,该变化趋势与试验结果一致。硫化交联可以有效提高橡胶分子之间的刚度,限制分子链发生移动,导致摩擦界面相对原子浓度和橡胶分子均方位移减小;橡胶分子刚度增加,使得橡胶基体与铁基板的相对位移增大,铁基板移动需要克服更多的原子性黏结,即黏附摩擦力增加,导致摩擦界面摩擦因数增大;而相对位移增大也导致更多的能量损耗,使摩擦界面产生更多的热量,摩擦界面温度上升。

Molecular dynamic tribological models for vulcanized nitrile rubber with different crosslinking densities(0.4, 0.8, 1.2, 1.6)-iron substrate were established, and then the effect of the crosslinking density on the friction coefficient, relative atomic concentration, friction interface temperature and mean square displacement of rubber molecular in shear friction were analyzed. The accuracy of the model was experimentally verified. The results show that with the increase of crosslinking density, the friction coefficient of the friction pair of vulcanized nitrile rubber-iron substrate increased;the change trend was consistent with the test results. Vulcanization crosslinking could effectively improve the stiffness between rubber molecules, and restrict the movement of molecular chains, resulting in a decrease in the relative atomic concentration at the friction interface and the mean square displacement of rubber molecules. The increase in the stiffness of the rubber molecular improved the relative displacement between the rubber matrix and the iron substrate, and the moving of iron substrate needed to overcome more atomic bonding;so the adhesion friction force increased, resulting in an increase in the friction coefficient of the friction interface. The increase in the relative displacement also led to more energy loss, making the friction interface generate more heat;so the temperature of the friction interface rose.