Study On Mechanical And Thermal Properties Of Soy Protein Isolate Modified Carbon Nanotube/epoxy Nanocomposite

Epoxy resin is widely used for aerospace,electronic device and packaging applications duo to its good adhesion,corrosion resistance,its ease of processing and the like.Especially in the field of electronic packaging,with the continuing miniaturization and increasing power density of elcetronic equipment,pure epoxy with poor toughness and low thermal conductivity is difficult to rapidly dissipate a large amount of heat genernated by electronic devices,which seriously affects the reliability and service life of device.It can be seen that the development of epoxy resin with synergistic enhancement of mechanical and thermal properties has been of great importance for the development of high-power density electronic devices.In this paper,carbon nanotube（CNT）was selected as nano filler,and soy protein isolate（SPI）was used to improve the dispersion and interfacial properties between CNT and epoxy,so as to effectively improve the thermal and mechanical properties of epoxy.The effect and mechanism of SPI on the thermal-mechanical properties of carbon nanotube/epoxy were revealed by molecular dynamics simulation and effective medium theory.The specific work and results are as follows:The dispersion efficiency and quality of soy protein isolate modified carbon nanotubes（SPI-CNT）aqueous solution were studied by the transmission electron microscope,ultraviolet visible spectrum and dynamic light scattering particle size analyzer.The treatment process of SPI-CNT was optimized,and the SPI-CNT solution with long-time（30days）dispersion and stability was obtained.By analyzing the hydrogen bond of SPI-CNT/H₂O and SPI-CNT/epoxy systems,the mechanism of SPI enhancing the dispersibility of SPI-CNT through hydrogen bond was explained.The influence of SPI on the interfacail mechanical properties of CNT/epoxy was studied by molecular dynamics simulation.SPI effectively improved the interface interaction of CNT/epoxy,resulting in the increase of the shear strength of SPI-CNT/epoxy interface by 26.9%.Combined with the mean square displacement analysis of CNT,it is clarified that SPI enhances the load transfer efficiency between CNT and epoxy interface throughπ-πstacking and CH-πinteraction.The in-situ tensile and fracture toughness of soy protein isolate modified carbon nanotube/epoxy（SPI-CNT/epoxy）were tested.The results showed that the Young’s modulus,tensile strength and fracture toughness of SPI-CNT/epoxy were 27%,24%and 32%higher than those of raw carbon nanotube/epoxy（Raw-CNT/epoxy）,respectively.The in-situ tensile fracture process of SPI-CNT/epoxy was further analyzed,and combined with the full field strain analysis and SEM images of fracture section,the corresponding crack propagation mechanism was proposed to clarified the mechanism of SPI improving the mechanical properties of CNT/epoxy.Through the calculation of CNT thermal conductivity,the influence mechanism of SPI on CNT thermal conductivity was analyzed,and the enhancement mechanism of heat conduction between SPI and CNT was revealed by the phonon state vibration energy spectrum.The internal relationship between the volume fraction,aspect ratio,interfacial thermal conductance,intrinsic thermal conductivity of SPI-CNT and the thermal conductivity of SPI-CNT/epoxy wsa established by the effective medium theory.In the same volume fraction,adding SPI-CNT with large aspect ratio,high intrinsic thermal conductivity or high thermal conductance can significantly improve the thermal conductivity of the composites.A corresponding heat transfer mechanism was proposed to reveale the thermal conductivity enhancement effect of SPI on carbon nanotube/epoxy.By calculating the change of volume with temperature of epoxy-SPI,it was confirmed that the interaction between SPI and epoxy can improve the glass transition temperature and thermal expansion coefficient of epoxy.