Molecular-scale investigation on relationship between thermal conductivity and the structure of crosslinked epoxy resin

Epoxy resins are widely used as matrix resins in many fields due to their excellent physical and mechanical properties. However, their low thermal conductivities restrict their applications, especially in electronic packaging. In this work, nonequilibrium molecular dynamics (NEMD) simulations were used to investigate the relationship between thermal conductivity and epoxy resin structure. Three systems, diglycidyl ether of bisphenol A (DGEBA)/4,4’-diamino diphenyl sulfone (4,4’-DDS), DGEBA/diethylene triamine (DETA), and tetraglycidyl diamino diphenyl methane (TGDDM)/4,4’-DDS, were simulated based on our previous crosslinking algorithm. The thermal conductivity of DGEBA/4,4’-DDS increased with the degree of crosslinking, which is due to increases in new thermal pathways through crosslinking bonds. The sequence of thermal conductivities was found to be TGDDM/4,4’-DDS > DGEBA/DETA > DGEBA/4,4’-DDS which was quantitatively validated with our experimental measurements, consistent with the sequence of crosslink density. To explore the microscopic mechanism governing thermal conductivity, separate heat transfer modes were investigated, revealing that the thermal conductivity contribution of bonded interactions dominates over that of non-bonded interactions for all three systems. This finding verifies that introducing crosslinking bonds dominantly contributes to higher thermal conductivity in epoxy materials. Our research provides suggestions for large scale manufacture of higher thermal conductive epoxy resins.