Surface Functionalization Of Sic For Prepartion Of High Thermally Conductive Elastomer Composites

With the advent of the 5G era,electronic components are tending towards integration and miniaturization.The heat dissipation under high-frequency damages the performance of electronic components and shorts their service life.Therefore,it is necessary to prepare thermal interface materials with simple manufacturing processes and excellent heat dissipation performance to meet the rapid heat dissipation needs of electronic components.Elastomers have high elasticity and easy processing,which can be prapred as thermal interface materials to solve the heat dissipation problem of electronic components.However,the thermal conductivity（λ）of elastomers is low,which limits their widespread application.In order to improve theλof elastomers,the silicon carbide（SiC）with relatively highλand excellent insulation was used as fillers to prepare high thermally conductive elastomer composites.However,the interface compatibility between the SiC fillers and the elastomer matrix is poor,resulting in a large interface thermal resistance（ITR）.Moreover,the SiC fillers is prone to forming aggregates in the polymer matrix,making it difficult to form continuous heat conduction channels,resulting in a limited increase in theλof composite.To solve these problems,the SiC was surface functionalized to improve the interface compatibility between the fillers and the matrix,reducing the ITR of the composite and constructing heat conduction channels in elastomer composites.In this thesis,three types of high thermally conductive elastomer composites were prapred.Non-covalent modification of SiC particles was firstly carried out using poly（caffeic acid/polyamine）（PCPA）,followed by covalent modification using 3-mercaptopropyltriethoxysilane（Si747）,resulting in the SiC-PCPA-Si747 thermally conductive fillers.Then,SiC-PCPA-Si747was filled into a natural rubber（NR）matrix to prepare SiC-PCPA-Si747/NR elastomer composites with highλ.The non-covalent modification of PCPA protected the intrinsicλof SiC,while the covalent modification of Si747 enhanced the interfacial compatibility between SiC and the NR matrix,resulting in lower ITR and improved phonon transfer efficiency in the composite.Theλvalue of the 50 vol%SiC-PCPA-Si747/NR composite reached 0.4980 W/（m K）,which was about 4.75 times of pure NR.In addition,SiC-PCPA-Si747/NR elastomer composites still exhibited good insulation performance.SiC was first modified using polydopamine（PDA）and further decoated with silver（Ag）nanoparticels with in-situ chemical plating to prepare SiC-P-Ag hybrid fillers.Then,SiC-P-Ag hybrid fillers was incorporated into an epoxidized natural rubber（ENR）matrix to produce rubber composites（SiC-P-Ag/ENR）with excellentλand dielectric properties.The PDA modification improved the interfacial interaction between SiC and the ENR matrix,reducing the ITR of the composites.Due to the construction of the SiC heat conduction channels and anchoring of Ag nanoparticles,theλof 50 vol%SiC-P-Ag/ENR composite was increased to 0.5655 W/（m K）,which was 5.39 times that of pure ENR（0.1048 W/（m K））.In addition,due to the formation of a micro-capacitor effect of Ag nanoparticles in the ENR elastomer composites,a high dielectric constant of 35 at 10 Hz and good insulation properties were obtained.Tannic acid（TA）and Fe³⁺were first used to chelate the surface of SiC particles.Then,the graphene oxide（GO）was further grafted onto its surface by hydrogen bonding interaction to prepare SiC-TA/Fe-GO hybrid fillers.Next,the SiC-TA/Fe-GO hybrid fillers was dispersed into a carboxylated nitrile rubber（XNBR）matrix using a co-precipitation method to prepare SiC-TA/Fe-GO/XNBR elastomer composites with highλand excellent insulation.The chelation layer of TA/Fe protected the surface properties of SiC particles and provided a secondary reaction platform for GO grafting.More importantly,the hydrogen bonding interaction between SiC-TA/Fe-GO and XNBR significantly reduced phonon scattering in the elastomer composites,leading to an effective increase inλ.In addition,the three-dimensional network structure of SiC-TA/Fe-GO in the XNBR matrix further improvedλ.The results showed that theλof 50 vol%SiC-TA/Fe-GO/XNBR composite material reached 0.5401 W/（m K）,which was2.93 times that of pure XNBR（0.1843 W/（m K））.In summary,surface functionalization of SiC can effectively improve theλof elastomeric composites,which also provide ideas for the preparation of other functional elastomer composites.