Preparation Of High Thermal Conductivity Insulating Elastomer Composites By New Surface Modifications

With the advent of the 5G technology,the electronic components are rapidly developing in the direction of high integration,power,digitalization,density,and high frequency,resulting in fast heat accumulation in electronic devices during operation and,in turn,severely affecting the reliability,stability,and service life.Therefore,preparation thermal interface material（TIM）with superior thermal conductivity（λ）has become a research hotspot.In this paper,new methods of surface modification were used to prepare several types of thermally conductive fillers,which were then filled into elastomer matrices to prepare high thermally conductive elastomer composites.In Chapter 3 of this paper,dopamine（DA）was self-polymerized on the surface of hexagonal boron nitride（BN）particles to introduce polydopamine（PDA）,and then silver（Ag）nanoparticles were deposited on the surface of BN-PDA particles by silver mirror reaction to prepare BN-PDA-Ag particles with core-shell structure.The prepared BN-PDA-Ag particles were next filled into methyl vinyl silicone rubber（SR）matrix to prepare silicone rubber composites with excellent electrical insulation and high thermal conductivity.PDA improved the interfacial compatibility between BN particles and SR and reduced the interfacial thermal resistance of the composites.High thermal conductivity Ag particles further improved the thermal conductivity properties of BN-PDA-Ag/SR composites,meanwhile,due to the Coulomb blocking effect of Ag nanoparticles,BN-PDA-Ag/SR composites still maintain high electrical insulation.The results showed that the thermal conductivity of 30 vol%BN-PDA-Ag/SR composite was0.75 W/m K,which is 5.77 times that of silicone rubber.At the same time,the alternating current（AC）conductivity of the 30 vol%BN-PDA-Ag/SR composite at 100 Hz was 1.89×10^-11 S/cm,indicating that the BN-PDA-Ag/SR composites still have excellent electrical insulation.In Chapter 4 of this paper,firstly,poly（catechol-polyamine）（PCPA）were modified on the surface of micron alumina（Al₂O₃）particles and further grafted with graphene oxide（GO）to prepare alumina@poly（catechol-polyamine）@grapheneoxide（Al₂O₃@PCPA@GO）multilayer core-shell particles.Al₂O₃@PCPA@GO particles were then dispersed into carboxyl nitrile rubber（XNBR）latex to prepare high thermal conductivity insulating elastomer composites.The abundant hydroxyl（-OH）,carboxyl（-COOH）,carbon oxygen double bonds（-C=O）and epoxy groups on GO can form hydrogen bonds with the polar cyano group（-C≡N）of carboxyl nitrile rubber.The carboxyl nitrile rubber elastomer composites showed electrical insulation properties,high thermal conductivity,and good mechanical properties.The results showed that theλof XNBR insulating elastomer composite filled with 30 vol%Al₂O₃@PCPA@GO particles was 0.48 W/m K,which is about 3 times that of pure carboxyl nitrile rubber.In Chapter 5 of this paper,firstly,polyrhodanine（PRd）was formed by oxidative polymerization of rhodanine（Rhd）which initiated by adsorbed disulfate ion（S₂O₈）^2-on the surface of BN particles.Due to the existence of acceptor N-C=S group in PRd,the surface of BN-PRd was grafted onto the molecular chains of epoxy natural rubber（ENR）by mechanochemical method,and ultra-thin thermally conductive insulating elastomer composites with anisotropy thermal conductivity were prepared by vacuum suction filtration.There were stable covalent bonds between PRd and ENR molecular chains,and the grafted ENR molecular chains acted as bridges between adjacent BN particles to form heat conduction channels,which improved the heat conduction capacity of the BN-PRd/ENR composites evidently.The results showed that the out-plane thermal conductivity（λ_⊥）and in-plane thermal conductivity(λ_//)of 30 wt%BN-PRd/ENR flexible insulating elastomer composite were0.52 W/m K and 14.57 W/m K,which are 2.89 times and 8.094 times of pure epoxy natural rubber（0.18 W/mK）,respectively.