Distribution Controlling And Thermal Conductive Network Regulation Of Thermal Conductive Filler In PVDF/PA6 Blends

With the miniaturization and high speed densification of electronic devices,it becomes more and more urgent to extend the life of computers,automobiles and aviation equipment by effective thermal management.The thermal conductivity of polymer composites filled with high thermal conductivity inorganic filler can be improved significantly.However,traditional fillers need a high filling quantity to form a heat conduction path,so as to obtain an ideal heat conduction effect.However,the high filling quantity not only increases the cost of material preparation,but also significantly reduces the mechanical properties and machining properties of the composites.In order to obtain ideal thermal conductivity at a low filling amount,MWCNTs-NH2 and MWCNTs-NH2/GNPs were used as thermal conductivity fillers in this paper,and polyamide 6(PA6)/polyvinylidene fluoride(PVDF)blends were selected as the matrix to prepare composite materials with double percolation structure,and thermal conductivity pathways were constructed by regulating the selective distribution of fillers in the two phases.The details are as follows:A thermodynamic and kinetic method based on the selective distribution and migration of MWCNTs-NH2:in polymer blend was reported to improve thermal/electrical conductivity of PA6/PVDF composites.Trapping MWCNTs-NH2 at the interface of PA6/PVDF blends could be achieved through two-step mixing process and subsequent migration.SEM,TEM and selective extraction confirmed that MWCNTs-NH2 could migrate from the PVDF phase to the two-phase interface during melt compounding.The composites could form a percolated conductive pathway and significantly improving thermal and electrical conduction capacity of the composites with low dose.At 1wt%MWCNTs-NH2,the thermal conductivity of A/(F/CN)composite was 0.46 W·m-1·K-1,which gained an improvement of 116.4%compared to F/A composite.The electrical resistivity is decreased to 107 ?·m,much lower than the electrical resistivity of the F/(A/CN)sample.The thermal infrared characterization also indicated that A/(F/CN)composites have better heat absorption and heat dissipation than other materials.Rheological measurements exhibit the presence of MWCNTs-NH2 network structure at a lower content of MWCNTs-NH2 for the A/(F/CN)composites.These results manifest that the thermal and electrical conductivity with low filler loading in blends and resultant performance of the composites can be greatly improved by selective distribution of MWCNTs-NH2 and controlling the migration process.The solution ultrasonic stripping method was used to disperse the GNPs and MWCNTs-NH2 thermal conducting fillers,which were dispersed in the PA6 matrix,and then mixed with PVDF to prepare a kind of composite material with two fillers(F/AxCNyP).The results showed that ultrasonic stripping was beneficial to the uniform dispersion of GNPs and MWCNTs-NH2 in PA6 phase,making the fillers network more compact.The thermal conductivity test results showed that the selective distribution of GNPs/MWCNTs-NH2 double fillers had a synergistic effect on the thermal conductivity improvement of the composite.The thermal conductivity of F/AlCN19.5P composites was 1.113W·m-1·K-1,which was 51%higher than that of F/A8CN composites.XRD and DSC results showed that the addition of GNPs/MWCNTs-NH2 filler did not affect the crystal types of PVDF and PA6,but changed the melting crystallization behavior of PA6 component and reduced the crystallinity of PA6 component in the composites.The observation of the microsection morphology shows that the "double-double" network structure formed by GNPs/MWCNTs-NH2 fillers in the PVDF/PA6 matrix and the reverse rotation of the rotor may cause the orientation of one-dimensional MWCNTs-NH2 and high-content two-dimensional GNPs along the direction of the shear force in the PA6 phase,and the synergetic effect produced by them can greatly improve the thermal conductivity of the composites.