Effects of nanoparticles and surface modification on thermal, mechanical, and electrical properties of composites from liquid silicone rubber with expanded graphite

In this study, expanded graphite-poly­(dopamine)-silver (EG-PDA-Ag) hybrid nanoparticles were synthesized in situ using a simple and environmentally friendly method. The EG nanoparticles were first PDA-modified by oxidative self-polymerization reaction of dopamine (PDA) in weakly alkaline aqueous solution, and then Ag nanoparticles were anchored to the surface of EG-PDA nanoparticles by the reduction of Ag + by ascorbic acid. The obtained EG-PDA-Ag nanoparticles were subsequently incorporated into a vinyl-methyl-silicone rubber (VMQ) matrix to generate composites with high thermal conductivity. The PDA surface modification effectively reduced the interfacial thermal resistance between EG and VMQ substrate, while the silver nanoparticles effectively established a three-dimensional thermal conductivity network. 10 wt % of EG-PDA-Ag/VMQ composites had a thermal conductivity as high as 1.15 W/mK. This value is six times higher than that of pure VMQ (0.18 W/mK). In addition, the EG-PDA-Ag/VMQ composites exhibit excellent electromechanical and mechanical properties. In conclusion, the proposed method is promising for the future preparation of high thermal conductivity dielectric materials.