Molecular Dynamics Simulation Of Mechanical Properties Of Graphene Oxide/Polymer Composites

Graphene oxide(GO)is a derivative of graphene,containing a large number of functional groups,such as carboxyl,hydroxyl and carbonyl.Due to the existence of these oxygen-containing functional groups,GO can be well dispersed in water and several other polymer matrix.Furthermore,its mechanical properties are similar to graphene,and it is cheaper and easier to process or produce than graphene.These properties will enable graphene oxide to be a promising nano-filler in the future.In this paper,the mechanical properties of graphene oxide/polymer composites [nylon 66 and styrene butadiene rubber(SBR)] were studied by molecular dynamics simulation and ReaxFF potential.For the research of graphene oxide/nylon 66 composites,two models of graphene oxide/nylon 66 composites and pure nylon 66 had be built by Materials Studio software firstly.Then the mechanical properties,Young's modulus and yield strength of these two models were investigated by uniaxial tensile simulation.The results show that the graphene oxide could be dispersed in the nylon 66 matrix uniformly and stably,and the Young's modulus and the yield strength of the composite are 49% and 27% higher than those of pure nylon 66.In addition,the glass transition temperatures of the two models were measured,and the results show that the glass transition temperature of the composite is higher than that of pure nylon.Finally,the hydrogen bond between graphene oxide and nylon 66 was analyzed.It is found that every GO nano-meter piece can be formed 5-6 intermolecular hydrogen bonds with nylon 66,which would improve bonding force between graphene oxide and nylon 66.Based on these simulation results,we proposed a strengthen mechanism of mechanical properties between graphene oxide and nylon 66.In the study of GO/SBR composite,the mechanical properties of SBR and GO/SBR composite have be investigated by uniaxial tensile simulation firstly,and then the hardness and the friction properties have be calculated by establishing an iron-subject material-iron three-layered model.The binding energy and hydrogen bond energy between GO and SBR have be also calculated during the friction process.The results show that the Young's modulus and hardness of the composite is 77% and 20.3% higher than those of pure SBR,respectively.The friction coefficient and wear rate are 18% and 38% lower than those of pure SBR,respectively.During the friction process,hydrogen energy and binding energy between GO and SBR have increased from 28.7 kJ/mol to 89.3 kJ/mol and 463.45 kJ/mol to 867.18 kJ/mol,respectively.This fact implies that there is strong interaction between GO and SBR,leading to the improvement of mechanical properties of SBR.