Barrier properties of thermal and electrical conductive hydrophobic multigraphitic/epoxy coatings

Epoxy composites doped with different content of graphene nanoplatelets (GNPs) and/or carbon nanotubes (CNTs) have been manufactured. Their chemical, thermal, electrical, and mechanical behaviors have been studied, evaluating also their performance as coatings of glass fiber composite substrates. It is confirmed that the graphitic nanofillers present different efficiency as nanofillers as a function of their geometry. CNTs are much higher efficient electrical nanofillers than graphene, but an important synergetic effect is determined in the electrical conductivity of hybrid GNP/CNT/epoxy composites. In contrast, the thermal conductivity scarcely depends on the geometry of graphitic nanofillers but on the graphitic nanofiller content. Adding up to 12 wt% GNP and 1 wt% CNT, the thermal conductivity of the epoxy resin can be increased more than 300%. GNP presents high efficiency to increase the barrier properties, reducing the water absorption up to 30%. The stiffness of nanocomposites proportionally increases with graphitic addition, up to 50%, regard to the modulus of the neat epoxy resin. The adherence of coatings over glass fiber composite substrates increases by nanofiller addition due to the nanomechanical anchoring. However, the water uptake induces a higher weakening on nanodoped composites due to the preferential water absorption by the interface.