Synergetic Effect of Graphite Nanosheets and Spherical Alumina Particles on Thermal Conductivity Enhancement of Silicone Rubber Composites

Small amounts (1-5 phr) of graphite nanosheets (GNSs) were added to highly filled spherical alumina (S-Al2O3)/silicone rubber (SiR) composites by the direct mechanical compounding method with a double planetary mixer. The morphology, filler network structure, and thermal conductivity of the resultant composites were investigated systematically. The results revealed that nanoscale dispersion of GNSs was achieved and the dispersion level was obviously improved with the presence of S-Al2O3. The addition of small amounts of GNSs can greatly increase the thermal conductivity of the highly filled S-Al2O3/SiR composites. For instance, the thermal conductivity of the composite filled with 300 phr of S-Al2O3 was increased from 1.103 to 2.162 W/(m K) by the addition of only 5 phr of GNSs, corresponding to an improvement of similar to 96%. We discovered that GNSs and S-Al2O3 exhibit a synergetic effect on the thermal conductivity improvement of the composite and the extent of synergy depends on both the loading and composition of the hybrid fillers. (C) 2016 Society of Plastics Engineers