Graphene and boron nitride nanoplatelets for improving vapor barrier properties in epoxy nanocomposites

Enhancement of barrier properties of coating materials are essential for potting sensitive electronic devices to prevent moisture penetration, in addition to enhancement of thermal conductivity required to facilitate efficient thermal management. The barrier of polymers is significantly improved by inclusion of impermeable 2D fillers. Clays, which are the most common "barrier-modifier" for polymers, are less effective for reducing water vapor permeability since they absorb water and swells. In this communication we focus on the addition of Graphene and Boron Nitride Nano Platelets (GNP and BNNP) as an alternative to clay, both are known to be impermeable to most gases and liquids. Alignment of the fillers within the matrix has a substantial effect on the barrier properties. Therefore, the nanocomposite was applied on a surface by a rod coating method. The larger aspect ratio ((similar to)700) of the GNP filler (compared to BNNP) results in an alignment perpendicular to the vapor flow upon rod-coating. As a result, the GNP-loaded polymer film provided more substantial barrier enhancement (80% reduction in permeability) than the BNNP-loaded film (60% reduction). Moreover, the thermal conductivity enhancement of the pristine epoxy matrix (0.2 W/(mK)) was higher when loaded with GNPs (2.18 W/(mK)) than with the BNNPs (0.57 W/(mK)), most probably due to the high intrinsic thermal conductivity and larger aspect ratio of the former.