GNPs-MWCNTs Enhance The Electrical And Thermal Conductivity Of TPU And 3D Printing

The trend of continuous miniaturization leads to unprecedented power density inside electronic devices,which also becomes a bottleneck for device performance improvement.Effective cooling of electronic devices is essential,and polymer materials,with their advantages of low cost,corrosion resistance,light weight,and flexibility,can play an important role in this important direction.However,there are some problems such as less choice of materials,low strength and single function.In this paper,the method of solution mixing and melting composite is mainly used to introduce functional fillers into the polymer matrix.By adjusting the type of functional fillers added and the mass ratio of fillers in the matrix,the composite material can meet the needs of 3D printing and improve the electrical and thermal conductivity of the material.By using the shear force generated by extrusion 3D printing during extrusion to induce the orientation of functional fillers,the performance of polymer composites can be optimized and improved by adjusting the printing parameters,printing paths,and multi-material combinations.The main research contents are divided into the following two aspects:（1）The thermoplastic polyurethane solution ink with appropriate concentration was successfully configured by a simple solution blending method.The direct ink writing（DIW）was used for molding,and the thermoplastic polyurethane composite samples with stable structure were printed by controlling the temperature of the printing platform,which provided a new idea for the molding of complex structures of thermoplastic polymers.By combining the high thermal conductivity and electrical conductivity of the nano-fillers with the 3D printing method,the thermal conductivity of the polymer composite prototyping sample along the printing direction（perpendicular to the YZ plane）was increased from 0.36 W·m^-1·K^-1 to 2.87 W·m^-1·K^-1,an increase of nearly 7 times.The highest conductivity was 5.49×10^-2 S·m^-1.The simple DIW method can be used to fabricate thermoplastic polymer composite devices with complex structures of both electrical and thermal conductivity.（2）Samples with electrical and thermal conductivity were successfully printed by the method of first solution composite,then melting composite and direct screw extrusion molding.Melt composite one-step molding can greatly improve the utilization rate of materials.The comparison of the performance of the composite printing samples with one-component and two-component fillers shows that the two fillers with different shapes achieve a good synergistic effect in the polymer matrix.The thermal conductivity of 10 wt%（MWCNTs:GNPs=1:3）-TPU reached 2.39 W·m-1·K-1 with the same mass fraction of filler.The conductivity of 10 wt%（MWCNTs:GNPs=1:3）-TPU was up to 1.5×10^-2 S·m^-1 compared to that of the composite filled with one component.