Preparation And Properries Of PA6/Al₂O₃ Thermally Conductive Composites

With the development of miniaturization,integration,high density and high speed of electronic components,heat dissipation of electronic components had became a very serious problem.Traditional inorganic materials such as metals and ceramics had not been able to meet the needs of further development of electronic products.And new high-efficiency heat-conducting materials must be used to discharge heat in time.The thermal conductive polymer composite material had excellent thermal conductivity and had the advantages of good molding processability,high electrical insulation,good corrosion resistance and high specific strength,etc.In present research,the engineering plastic nylon 6（PA6）,which could coat a large amount of filler and had excellent properties,was selected as the resin matrix.The alumina（Al₂O₃）with excellent thermal conductivity and stable property was used as the main thermal filler.Carbon nanotubes（CNTS）were added as an auxiliary heat conductive filler.The thermally conductive composites,thermal conductivity,mechanical properties,thermal properties and micro-interface properties were investigated.The effects of the particle size and the amount of the filler,the type and amount of the coupling agent,and the type and amount of the carbon nanotubes were discussed.（1）Four different particle sizes of Al₂O₃（5um,10um,30um,50um）were selected.The effects of Al₂O₃ dosage,particle size and blending process on the properties of the composites were investigated.The results showed that with the increase of Al₂O₃ addition,the thermal conductivity of the composites increases,and the tensile strength first rises and then decreases,the impact strength and elongation at break decrease.Blending with a three-screw extruder can greatly improve the thermal conductivity and mechanical properties of the composite material,and the production efficiency was high.（2）In order to further improve the interfacial dispersion between the thermally conductive filler and the resin matrix,a coupling agent was used to surface-treat the inorganic filler.Three different coupling agents were selected:silane coupling agent,titanate coupling agent,and self-made coupling agent.The results showed that the self-made coupling agent had higher activation rate and oil absorption value,and the efficiency of processing inorganic filler was higher;the compatibility of the composite material could be greatly improved,and the thermal conductivity and mechanical properties of the coupling agent could be improved.（3）In order to improve the thermal conductivity of the thermally conductive filler,further reduce the turbulence of the thermally conductive filler,and the carbon nanotubes were added to the PA6/Al₂O₃ thermal composite material to construct a three-dimensional thermal conduction system.The results showed that functionalization could improve the dispersion of carbon nanotubes in composites,but functionalization would also reduce the thermal conductivity of carbon nanotubes.After the multi-walled carbon nanotubes were functionalized,the thermal conductivity decreases little,and the aspect ratio does not increase the thermal conductivity.After the formulation was improved,The diffusion ability of the carbon nanotubes was greatly improved.