A Study On Friction And Wear Mechanism Of Vulcanized Styrene-butadiene Rubber Based On Molecular Dynamics Simulation

Vulcanized rubber is widely used in the field of tribology due to its excellent mechanical and physicochemical properties.The experimental study on the macro-tribological properties of vulcanized rubber has been very mature and has an important position.However,the work of studying the friction and wear mechanism of vulcanized rubber from the microscopic scale is still lacking.Therefore,the friction and wear model of vulcanized styrene-butadiene rubber were established by molecular dynamics method.The effects of vulcanization on the mechanical properties of styrene-butadiene rubber and the microscopic mechanism of improving the friction and wear properties were studied from a microscopic perspective.First,the styrene and butadiene are used as repeating units to construct the geometric configuration of styrene butadiene rubber.The molecular model of raw styrene butadiene rubber is obtained by geometric optimization,annealing simulation and equilibrium simulation with the COMPASS force field.The vulcanized styrene butadiene rubber model is obtained by imposing the self-designed vulcanization algorithm to crosslinking the raw styrene butadiene rubber.The rationality of the model was verified by the glass transition temperature.On this basis,by comparing the structural and dynamic mechanical properties of vulcanized styrene butadiene rubber with raw rubber,the effect of vulcanization on the relevant physical properties of styrene butadiene rubber was studied.Secondly,a friction model of vulcanized rubber-iron matrix was constructed,the atomic concentration,temperature distribution,radial distribution function,and interface energy were calculated.It was found that the introduction of the crosslinking structure can limit the movement of molecular chains and hinder the movement of rubber atoms to the friction area,which can reduce the adhesion effect,reduce the deformation of the rubber and the interface temperature,and reduces the friction coefficient and tribological stress,improving tribological properties.Third,the effect of temperature,load and sliding speed on the friction coefficient of vulcanized styrene-butadiene rubber was studied by using MFT-R4000 high-speed reciprocating friction and wear tester.After comparing the experimental results with the simulation results,it was found that the friction coefficients of the two showed a trend of increasing first and then decreasing,which verified the accuracy of friction simulation from a qualitative perspective.As for the factors of load and sliding speed,there is also a certain relationship between the macro experiment and the micro simulation.Finally,the wear model between vulcanized rubber and iron pin is constructed,some key phenomena of micro friction wear such as unwrapping and stretching of molecular chains,adhesion,interface failure,and peeling of some materials were captured.The introduction of crosslinking structure reduces the abrasion phenomenon mentioned above,thereby reducing the damage of the matrix and improving the tribological properties.The effects of different interface parameters on the micro wear properties of vulcanized rubber were also studied.The molecular dynamics model of vulcanized rubber was established in this study.The mechanism of crosslinking structure to improve the micro friction and wear performance of rubber was studied from nanoscopic perspective.The work enriches the research content of rubber tribology,and provides a theoretical basis for reference to further improve the tribological properties of rubber.