High Thermal Conductivity Polyurethane-Boron Nitride Nanocomposite Encapsulants

An experimental investigation has been conducted to determine the effect of adding boron nitride (BN) nanoparticles on the thermal conductivity of polyurethane nanocomposites. BN nanoparticles (average size of 70 nm) were functionalized using three different materials: acetone, nitric acid, and an alkoxysilane. Various weight fractions of the alkoxysilane-coated particles were incorporated into a polyurethane via shear mixing and ultrasonication. The dispersion of nanoparticles within the fabricated nanocomposites was verified using fieldemission scanning electron microscopy (FE-SEM). Analysis of the FE-SEM images indicated that the particles were well dispersed in the polyurethane matrix, and functionalization with alkoxysilane improved BN adhesion to the polyurethane, as verified by water drop contact angle measurements. Thermal conductivity measurements, made using a thermal conductivity analyzer, indicated that non-functionalized BN particles (5% weight fraction) increased the thermal conductivity of the resulting nanocomposite by 50%, while the increase in thermal conductivity realized by the addition of the silane-treated BN particles was only about 20%. Additional testing is underway to determine why better thermal conductivity results were not obtained from the silane-treated BNpolyurethane nanocomposites.