Preparation And Properties Of Modified Graphene And Its Two-component Room Temperature Vulcanized Thermally Conductive Silicone Rubber

Graphene is two-dimensional atomic crystal in honeycomb shape that consists of sp²hybrid carbon atoms.This special structure bring about excellent mechanical,electrical conductivity,thermal conductivity properties,etc,which make it widely applied in the field of silicone rubber as special filler.However,graphene is hydrophobic and oleophobic,which make it difficult to disperse and easy to aggregate in water and organic solvents.These disadvantages greatly hinder the graphene from applying in silicone rubber.In this study,we have successfully prepared two kinds of modified graphene firstly.The first is functionalized graphene?FG?.The graphite oxide?GO?was functional modified with KH-792 and became FG by reduction reaction.The other modified graphene is hydrophobic SiO₂-coated graphene?HM-SiO₂-G?.The SiO₂ nanoparticles were coated on the surface of GO with sol-gel method.Then the SiO₂-G was restored and oleophylic modified to prepare HM-SiO₂-G.Then these two kinds of modified graphene were added into silicone rubber matrix respectively,the mixture was mixed up thoroughly and solidified in room temperature to prepare two-component room temperature vulcanized?RTV-2?thermally conductive silicone rubber.The morphology,chemical structure and dispersity of these two modified graphene were characterized with TEM,AFM,FTIR,Raman and XRD methods,etc.In addition,the heat-resistance behavior,mechanical properties,thermal conductivity and electrical conductiivity of the RTV-2 silicone rubber were also studied systematically.The experimental results show that the FG could disperse in ethanol,acetone and other organic solvents uniformly and it could be completely stripped into lamellae by ultrasonic dispersion.And the addition of FG could effectively improve the thermal stability,mechanical properties and thermal conductivity of RTV-2 silicone rubber,and the electrical insulation property was retained at the same time.When the additive amount of FG was 2 wt%,the thermal conductivity of RTV-2 silicone rubber was 63.1%higher than that of the pure RTV-2silicone rubber.When the addition amount of FG was 1 wt%,the volume resistivity of RTV-2silicone rubber was around 10¹²?·cm which could meet the requirements of the electrical insulation performance of potting adhesive in most occasions.However,when the addition amount increased to 2 wt%,the volume resistivity of RTV-2 silicone rubber decreased to 10¹⁰?·cm,which was not capable of serving as electronic potting adhesive.As for the second modified graphene,there were many obvious granular materials on the SiO₂-GO surface,which was owning to the SiO₂ nanoparticles coated on graphene oxide successfully.HM-SiO₂-G was dispersed in RTV-2 silicone rubber uniformly and there was no graphene lamellae or aggregates in rubber matrix.The addition of HM-SiO₂-G could effectively improve the thermal stability,mechanical properties and thermal conductivity of RTV-2 silicone rubber and had no great influence on the electrical insulation performance.HM-SiO₂-G as filler could improve the thermal conductivity of silicone rubber much better than traditional alumina filler.Only adding a small amount of graphene could greatly enhance the thermal conductivity of RTV-2 silicone rubber,which made it smaller specific gravity.This advantage was valuable in some places that required low density silicone rubber.The results show that when the addition amount of HM-SiO₂-G was 3 wt%,the volume resistivity of RTV-2 silicone rubber was about 10¹³?·cm.And its volume resistivity wouldn't be less than 10¹²?·cm as the addition amount increased,which could serve as ideal electronic potting adhesive.