Preparation And Thermal Conductivity Mechanism Of ZnOs@T-ZnOw/EP Composite

As electronic integration technology gathers momentum,heat dissipation performance of heat management materials is now facing higher requirements.At present,the research focus is mainly on the development of polymer composites with good thermal conductivity,high insulation performance,and excellent processing performance.In this work,epoxy resin composites were obtained through thermosetting curing process with spherical zinc oxide（ZnOs）,tetraneedle-shaped zinc oxide whiskers（T-ZnOw）as fillers,and epoxy resin as matrix.In this work,the effects of different morphology,filler content,and coupling agent modification processes on the thermal conductivity,insulation,and mechanical properties of the composite were studied.Through surface modification method,the filler matrix interface bonding ability was optimized,the interfacial thermal resistance was reduced,and the thermal conductivity was improved.The thermal conductivity mechanism of the composite material was explained through simulation.The main conclusions obtained are as follows:（1）ZnOs@T-ZnOw/EP composite materials were prepared with ZnOs and T-ZnOw as fillers.The results showed that the thermal conductivity of ZnOs@T-ZnOw/EP composite materials was significantly improved compared with that of pure epoxy resin,and the thermal conductivity of 40%ZnOs@60%T-ZnOw/EP composite materials was0.52W·（m·K）^-1,176%higher than that of pure epoxy resin;the impact strength of ZnOs@T-ZnOw/EP composite materials was slightly lower than that of pure epoxy resin,which decreased gradually with the rise of T-ZnOw content,and the impact strength of40%ZnOs@60%T-ZnOw/EP composite materials was 5.44 k J·m^-2.The Shore hardness of40%ZnOs@60%T-ZnOw/EP composite materials was basically maintained at 90 HD.The insulation performance of ZnOs@T-ZnOw/EP composite materials was lower than that of pure epoxy resin,which fall off with the increase of T-ZnOw content;40%ZnOs@60%T-ZnOw/EP composite had the lowest volume resistivity of 4.73×10¹⁰Ω·cm²,still higher than10¹⁰Ω·cm²,showing good electrical insulation performance.（2）The modified ZnOs@T-ZnOw/EP composite materials were prepared by selecting a silane coupling agent to modify the surface of zinc oxide powder.In this work,the effects of the types of silane coupling agents,the amount of coupling agents,the amount of fillers filled,and the ratio of fillers on the thermal conductivity,mechanical properties,insulation properties,and thermal stability of modified ZnOs@T-ZnOw/EP composite materials were studied.The experimental results displayed that when the filler content was 22.04 vol%,the KH550 silane coupling agent content was 4 wt.%,and the proportion of ZnOs and T-ZnOw content was 20%:80%,the thermal conductivity of the composites reached the highest value of 0.71W·（m·K）^-1,upped by 274%compared to pure epoxy resin;the mechanical properties of modified ZnOs@T-ZnOw/EP composite materials were significantly improved compared to unmodified composite materials,and the impact strength descended slowly with the increase in filler content.With the filler content of composite materials being 25.96 vol.%,the minimum impact strength was 5.66 k J/m^-2.Compared to unmodified composite materials,the insulation performance of modified ZnOs@T-ZnOw/EP composite materials was significantly improved,and the volume resistivity dropped with the up in filler content.However,the resistivity of modified composite materials remained above the order of 10¹²Ω·cm²,exhibiting excellent electrical insulation performance.（3）The heat conduction model was constructed through COMSOL Multiphysics,and the heat conduction effect of the model was simulated.The simulation results implied that the heat transfer effect of the 20%ZnOs@80%T-ZnOw thermal conductivity model was the best with the interfacial thermal resistance that hinders the improvement of the thermal conductivity of composite materials being mainly the filler-air contact thermal resistance and the matrix-air contact thermal resistance.The consistency between the simulation results and the actual experimental results confirmed the reliability of the experimental conclusions.In this work,a thermal conductivity model of ZnOs@T-ZnOw/EP composite materials was drawn based on simulation results and actual experimental results,further revealing its thermal conductivity mechanism.