Molecular Dynamics Simulation Study On Mechanical And Thermal Properties Of Polyisoprene

Rubber is a high-molecular composite material with a complex structure and composition.It is widely used in many fields,especially tires,seals and elastic materials.In order to meet these applications,rubber needs to meet the corresponding mechanical and thermal performance requirements,so the polymer and various additives need to be selectively selected and mixed to form an elastic composite material.Due to the complexity of the rubber system,it is difficult to observe the microscopic details in the experiment,and computer simulation can deeply understand the details of the substance from the microscopic perspective.In this paper,molecular dynamics(Molecular Dynamics Simulations,MD)were used to study the mechanical strength,heat generation and thermal conductivity of polyisoprene rubber(IR).First,the effects of cross-linking density,filler content,filler particle size,interface strength,temperature and strain rate on the mechanical properties and heat generation of IR were studied by MD method.The study found that the existence of the best cross-linking density minimizes the heat generation of the IR;the increase in the filling content and interface strength increases the mechanical properties and heat generation of the IR rapidly;the increase in particle size can reduce the heat accumulation,but the mechanical properties decrease;The temperature increases,the heat generation of IR decreases,and the mechanical properties also decrease;at high strain rates,as the strain rate increases,the mechanical properties and thermal properties of IR both increase significantly.Then heat generation performance of IR was studied by means of energy analysis.First,the analysis of kinetic energy and potential energy shows that the change of potential energy in the filled IR is much greater than the change of kinetic energy;then through the study of bonding energy and non-bonding potential energy,it is found that non-bonding potential energy is the main influencing factor in the change of potential energy;The non-bonding potential energy calculation of polymer-polymer(pp),polymer-filler(pf)and filler-filler(ff)found that pf non-bonding potential energy is the dominant factor of energy change.Finally,the effects of network structure,filler content,filler size,p-f interface strength and molecular chain orientation on IR thermal conductivity were investigated.The study found that the increase in cross-linking density can improve the thermal conductivity of polyisoprene within a certain range;the double network structure can further improve the thermal conductivity of cross-linked polyisoprene;the addition of fillers can improve the thermal conductivity of IR,which The increase of the pf interface strength is more obvious for the improvement of its thermal conductivity;the molecular chain orientation has a greater influence on the IR thermal conductivity of low crosslinking,low filling and low pf interface strength.The study found an important factor affecting the heat-generating properties of rubber materials,namely the strength of the interaction between the polymer segment and the filler.The simulation research results can help experimental design and manufacture of new rubber materials with high strength,low heat generation and good thermal conductivity.