Thermo-mechanical Properties Of Crosslinked Epoxy Resin:a Molecular Dynamic Simulation

In this paper,crosslinking process and thermo-mechanical properties of epoxy material composed of DGEBA/DGEBAEO-2 as the epoxy resin and DDS as the hardener have been investigated using molecular dynamic simulation.The influence of DGEBA/DGEBAEO-2 ratio and crosslinking density on structure and properties have been studied.In addition,the change of the Tg and mechanical properties of DGEBA/DGEBAEO-2 ratio and crosslinking density have been predictedAn efficient script to build molecular model between epoxy resin and amine curing agents has been developed,which was applied to monitor the crosslinking process and cooling process of an epoxy resin system composed of DGEBA/DGEBAEO-2 and DDS.The thermo-mechanical properties and structures with the change of epoxy resin ratio and crosslink density have been investigated.As a result of which,the best ratio for DGEBA/DGEBAEO-2 have been found.The result show that,with the increase of the DGEBAEO-2,crosslink density and elastic modulus shows an increasing trend at first and then decrease,and reaches the maximum when the mass fraction of DGEBAEO-2 is 50%.Glass transition temperature(Tg)shows a gradually decreasing in trend.Mean square displacement(MSD)can be used to measure the molecular chain flexibility in the system,the MSD shows that DGEBAEO-2 chain flexibility is higher than DGEBA chain flexibility in the system.The effect of crosslinking density on the system performance was studied.With the increases of crosslink density,The density of the structure increased and the volume shrinked,elastic modulus showed an increasing trend,glass transition temperature(Tg)showed the same trend.Non-bond energy like vdw and Electrostatic interaction increase with crosslink density's increase,however,total potential energy,angle energy and torsion energy reduce with it.Radial distribution function(RDF)was used to study the local structure of the epoxy and its evolution with the increase of crosslink density's.Mean square displacement(MSD)and fraction free volume(FFV)of the system were analyzed.The MSD of the system shows a decrement phenomenon and FFV shows an increasing trend at first and then a decrease with the increase of crosslink density's.The reason is that the crosslinking process forms the 3D network structure,which restricts the movement of the molecular chain.