Molecular Simulation Of Hydrogenated Nitrile Rubber Modified Stator For Electrical Submersible-motor-driven Progressive Cavity Pumping

With the rapid development of submersible screw pump oil recovery technology in China,the service life of its stator rubber also affects the use efficiency of the screw pump oil recovery system to a certain extent.Since hydrogenated nitrile rubber(HNBR)has excellent oil resistance and medium corrosion resistance,it is widely used in the aerospace and automotive industries;however,the research on the structural properties of hydrogenated nitrile rubber and its mechanical properties are mainly affected The factors are rarely discussed.In this paper,through molecular simulation technology,the physical and mechanical properties of hydrogenated nitrile rubber under the action of plasticizers are studied.At the end of aging,when the content of oxygen entering the molecular chain increases,the oxygen in the hydrogenated nitrile rubber system The mechanism of diffusion is discussed and analyzed.Finally,the effect of molecular chains of hydrogenated nitrile rubber with different degrees of polymerization on the tensile behavior is studied.The main conclusions are as follows:Odified hydrogenated nitrile rubber with dibutyl phthalate(DBP)plasticizer.Firstly,the solubility parameters and the radial distribution function molecular simulations were carried out to calculate the compatibility of the two.After modeling the blending system of hydrogenated nitrile rubber and DBP with different components,it is found that the addition of DBP plasticizer has a significant effect on reducing the glass transition temperature of hydrogenated nitrile rubber,and increases the applicable temperature of hydrogenated nitrile rubber range.Due to the brittleness of the nitrile rubber after being hydrogenated,the mechanical constant calculation of the blending system found that the hydrogenated nitrile rubber molecular chain had the best flexibility when the DBP plasticizer content was10%,and its elastic modulus can be reduced by about 20%,indicating that the proper addition of DBP can improve the ductility of hydrogenated nitrile rubber to a certain extent.Secondly,through the MD simulation of the oxygen diffusion phenomenon in the HNBR system,it is found that the free volume of the HNBR molecular chain increases with the increase of the oxygen fraction,indicating that the oxygen content affects the integrity of the molecular chain,resulting in an increase in the free volume of the system.In the calculation of the root mean square displacement,it was found that oxygen molecules would destroy the stability of the HNBR molecular chain;however,the presence of a large number of oxygen molecules had little effect on the stability of the system;indicating that small molecules had limited influence on the HNBR molecular chain.The radial distribution function of the HNBR molecular chain is calculated,and it is found that as the temperature increases,the coordinate at the position of the C-H bond and the C-C bond length decreases more obviously.Through Lammps simulation,it was found that at high temperature,oxidation will generate formaldehyde,acetaldehyde,methane,water,and hydroxyl radicals in HNBR diffusion,which corroborates the results of the calculation of the radial distribution function of the HNBR molecular chain.The molecular simulation of the same tear elongation was carried out on the four hydrogenated nitrile rubber molecular chains with different polymerization degrees.After the model was built,the tensile process was simulated and found that the higher the polymerization degree,the more obvious the molecular chain stress response.The stretching effect is even more.After analyzing the different potential energy of the system,it is found that with the increase of the degree of polymerization,the compactness of the system is enhanced,which affects the increase of van der Waals non-bonded potential energy;at the same time,the more entangled the molecular chain,the more the barrier energy needs to be As the degree of polymerization increases,the root mean square displacement(MSD)of the system also decreases.As the length of the molecular chain increases,its flexibility increases,which makes it easier for entanglement between chains.However,the MSD growth is not obvious after the polymerization degree reaches 50,indicating that the increase in the polymerization degree can affect the flexibility of the molecular chain and make the system more prone to entanglement,but the effect is limited.