Study On Thermal Oxygen Aging And Tribological Properties Of Molybdenum Disulfide/Nitrile Butadiene Rubber Composites

A submersible screw pump is one of the most widely used oil extraction devices in the subsea oil exploration industry.Its oil recovery function is achieved by the internal metal rotor and stator rubber through organic engagement.However,in the process of oil extraction,stator rubber was often subject to the coupling effects of various factors such as high temperature,high pressure,and strong corrosive media.This not only made the stator rubber extremely prone to fracture and wear failures but also greatly reduced the working efficiency of the submersible screw pump.Therefore,improving the wear,corrosion,and high-temperature resistance of stator rubber has very important practical significance.Nitrile butadiene rubber（NBR）was often selected as the base material for stator rubber due to its excellent wear resistance,oil resistance,and viscoelasticity.However,during oil extraction,NBR was often affected by harsh environments such as high temperature,high pressure,and sediment,making it difficult for pure NBR to meet the growing production demand.Therefore,it is urgent to improve the thermal oxygen aging and tribological properties of NBR.Traditional materials had disadvantages such as difficulty to degrade and limited reinforcement capacity.At the same time,new nano-reinforcing materials were expensive and polluting.Therefore,molybdenum disulfide（MoS₂）,which had a large specific surface area,excellent lubricity,and reinforcement ability,was selected as the reinforcement material.Due to the simplicity and efficiency of molecular dynamics（MD）,simulation can also effectively predict the material properties of complex systems.Therefore,this article used MD simulation,using NBR as the matrix,MoS₂ as the reinforcing material,and adding antioxidant 4020 to improve the thermal and oxygen aging performance of NBR.The purpose was to study the mechanical and tribological properties of NBR improved by MoS₂ from a microscopic perspective.At the same time,the thermal oxygen aging mechanism of antioxidant 4020 on NBR was analyzed from an atomic perspective.In this thesis,multiple groups of MoS₂/4020/NBR composites were prepared through experimental research.The purpose was to explore the effects of different mass fractions of MoS₂ on the mechanical and tribological properties of NBR.In this thesis,using MD simulation,two sets of models,4020/NBR and MoS₂/4020/NBR were constructed to study the effects of MoS₂ on the mechanical,thermal oxygen aging,and tribological properties of NBR.The results showed that compared to 4020/NBR,Young’s modulus of MoS₂/4020/NBR was increased by about 28%,a friction coefficient was increased（μ）It had been reduced by about 30% and the wear amount（W）had also been reduced by about 5%.At the same time,the addition of MoS₂ not only improves the compatibility between fillers but also improved the heat and oxygen aging properties of NBR.Then,using MD simulation,three models of Pure NBR,C₆H₁₂/NBR,and MoS₂/C₆H₁₂/NBR were constructed under the swelling conditions of cyclohexane(C₆H₁₂).The effects of MoS₂ on the swelling and tribological properties of NBR were studied.The results showed that C₆H₁₂ accelerated the movement rate of NBR molecular chains and decreased their various properties.At the same time,compared to C₆H₁₂/NBR,the tensile strength（TS）of MoS₂/C₆H₁₂/NBR increased by about 50%,and reduced use by about 20%.Therefore,the addition of MoS₂ effectively limited the movement of NBR molecular chains and improves the swelling resistance of NBR.Finally,MoS₂/NBR composites were prepared through experiments,and the effects of different mass fractions（0,0.5,1,2,3phr）of MoS₂ on the mechanical,thermal oxygen aging,and tribological properties of NBR were analyzed.The results showed that after adding MoS₂,TS showing a trend of first increasing and then decreasing,and μ Showing a trend of decreasing first and then increasing.The mechanical and tribological properties were the best when 2phr MoS₂ was added.Through the electron microscope,it was found that when 2phr MoS₂ was added,the holes and protrusions on the surface of NBR composites were the smallest and the surface was the smoothest.Therefore,this topic provided a new type of NBR composite material for the stator rubber of submersible screw pumps.