High thermal conductive epoxy resins with controlled high-order structure [electrical insulation applications]

The thermal conductivities of resins can be improved by introducing a high-order structure having microscopic anisotropy while maintaining their macroscopic isotropy. We studied four kinds of diepoxy monomers with a biphenyl group or two phenyl benzoate groups as mesogens, and cured them thermally with an aromatic diamine curing agent. Their thermal conductivities were up to 5× higher than those of conventional epoxy resins, because the molecular groups, mesogens, form highly ordered crystal-like structures which suppress phonon scattering. We confirmed the existence of crystal-like structures in the epoxy resins directly using TEM observation. We also observed mezoscopic structures in the resins using an AFM. The results suggest a novel method to improve the thermal conductivities by controlling the high-order structures. Furthermore, the laminates were prepared with the high thermal conductive epoxy resin containing a biphenyl group and ceramic fillers as a part of a feasibility study. Thermal conductivities more than 10× higher than ordinary epoxy resin laminates were obtained for test pieces of the laminates.