Experimental And Molecular Simulation Of Hydroxy Silicone Oil Modified Boron Nitride/Silicone Rubber Composites Research

Polymers are widely used as thermal interface materials in microelectronics and wireless communications,where materials with high thermal conductivity and low dielectric loss are required for effective thermal diffusion and signal transmission.Silicone rubber is a widely used thermal interface material because of its excellent dielectric properties,good flexibility and wide operating temperature range.However,the thermal conductivity of silicone rubber is low and often requires the addition of thermally conductive fillers to improve its thermal conductivity.Boron nitride has the advantages of good thermal conductivity and good insulating properties,and is an excellent thermal conductivity filler.However,the poor interfacial compatibility and weak interfacial interaction between boron nitride and silicone rubber are not conducive to the improvement of thermal conductivity and dielectric properties,and further modifications are needed.In this work,two hydroxysilicone oil modified boron nitride/silicone rubber composites were prepared by grafting boron nitride with hydroxysilicone oil(repeat unit number 5 or 11),which has a similar molecular structure to that of the silicone rubber matrix.Infrared spectroscopy,thermal weight loss analysis,X-ray photoelectron spectroscopy and X-ray diffraction showed that the molecular chains of hydroxysilicone oil were successfully grafted on boron nitride.In addition,the thermal conductivity and dielectric properties of the hydroxysilicone oil modified boron nitride/silicone rubber composites proved to have better thermal and dielectric properties compared to the unmodified boron nitride/silicone rubber composites.In addition,the boron nitride/silicone rubber composites modified with longer chain length of hydroxyl silicone oil Si11(repetition unit of 11)have excellent thermal and dielectric conductivity,and the silicone rubber composites with 40wt% of Si11 have improved thermal conductivity by 683.3% and enhanced dielectric breakdown strength by 73.2% compared with pure silicone rubber.Compared with the boron nitride/silicone rubber composite,its dielectric loss maximum was reduced by 74.5%,showing a better overall balance of thermal and dielectric properties.The microscopic mechanisms and influencing variables of the changes in thermal and dielectric properties of the modified boron nitride/silicone rubber composites were investigated by using molecular dynamics simulations.The simulation results show that the improvement of thermal conductivity is mainly related to the improvement of interfacial properties and the degree of phonon matching;the improvement of dielectric properties is mainly related to the improvement of interfacial compatibility and the enhancement of the strength of interfacial interactions.In addition,hydroxy silicone oil modified boron nitride Si20/silicone rubber composite system with longer chain length(20 repeating units)was constructed in this study,and the thermal and dielectric properties of hydroxy silicone oil modified boron nitride/silicone rubber composites with different chain lengths were predicted based on the simulated and calculated interfacial properties and thermal conductivity.The results show that the long chain silicone oil modified boron nitride Si20 is more favorable for the enhancement of the thermal and dielectric properties of the silicone rubber composites.This study explored the microscopic mechanisms of the changes in thermal conductivity and dielectric properties of BN/silicone rubber composites modified with different chain lengths at the molecular level,providing a theoretical basis for the modification and modulation of the composite interfaces.