Aqueous dispersion of submicron-sized diamond particles for thermally conductive polyurethane coating

To improve corrosion resistance of steel sheet, polymeric resin coating has been practiced in steel industry. However, this method has a drawback to use because polymeric coating layer decreases the thermal conductivity. With an aim to enhance the thermal conductivity of the polymeric coating layer on steel sheet, submicron-sized diamond (μD) particles were employed as a thermally conductive material. Various anionic and non-ionic surfactants were tested in order to stabilize heavy μD particles in aqueous phase. Among them, 1-pyrenecarboxylic acid (PCA) endowed the best stability to μD particles. The polyurethane-based coating layer containing PCA-stabilized μD particles was applied on the steel sheet. The thermal conductivity of the coating layer effectively increased from 0.351 W/(m K) (0 wt% μD) to 0.434 W/(m K) (for 1.0 wt% μD). Furthermore, the corrosion behavior was not observed upon salt spray test for 144 h.