Preparation And Properties Of High Thermal Conductive Polyimide, Poly(aryl Ether Ketone) Composites

With the development of LED lighting and microelectronic packaging technology,electronic components and electronic devices are developing towards miniaturization and high integration.With the improvement of electronic equipment performance,heat dissipation becomes a key problem.The demand for high thermal conductive materials is becoming more and more urgent.Thermal conductive polymers have the advantages of light weight,easy processing and chemical corrosion resistance,which are infiltrating into the application fields of traditional thermal conductive materials.In particular,the preparation method of filled thermal conductive polymer is simple,easy to mass production and low cost,which is a promising thermal conductive material.In the process of preparing thermal conductive polymers,thermal conductivity and mechanical properties can't be synchronously obtained,which limits the development and application of thermal conductive polymers.In this paper,polyimide and poly(aryl ether ketone)with excellent mechanical properties were used as matrix,and special polymer matrix composites with high thermal conductivity and high mechanical properties were obtained by improving the organic-inorganic interface,regulating the distribution state of fillers,constructing thermal conductive and mechanical networks and optimizing the packing arrangement of fillers,and all the composites had excellent thermal properties.The main research developments were as follows:(1)In order to reduce the interfacial thermal resistance between carbon nanotubes and polyimide,carbon nanotube-graft-polyimides(MWCNT-g-PIs)with different MWCNT contents were prepared by in situ grafting method.For comparison,carbon nanotube/polyimides(MWCNT/PIs)were prepared by simple blending method.Both MWCNT/PIs and MWCNT-g-PIs exhibited excellent mechanical properties with the tensile strength of 129 MPa,the tensile modulus of 2.59 GPa and the elongation at break of 36.1% for 10% MWCNT-g-PI.The thermal conductivity of MWCNT-g-PIs was better than that of MWCNT/PIs.The thermal conductivity of 10% MWCNT-g-PI increased 87.0% compared with PI.The interfacial thermal resistance of 10% MWCNT-g-PIs decreased by 16.7% at the same addition amount.(2)To further promote the formation of thermal conductivity pathways,we selected single-walled carbon nanotubes with a higher aspect ratio,while using polyvinylidene fluoride to induce their aggregation into bundles distribution in the polyimide matrix to improve the thermal conductivity of the composites.Single-walled carbon nanotube/polyvinylidene fluoride/polyimide composites(SWCNT/PVDF/PIs)were prepared by blending method.SWCNT/PVDF/PIs exhibited outstanding mechanical properties: the tensile strength of SWCNT/PVDF/PIs films was 119-105 MPa,the tensile modulus was 2.7-3.3 GPa and the elongation at break was 35.6-22.9%.The SWCNT/PVDF/PIs exhibited excellent thermal conductivity.The thermal conductivity of 3% SWCNT/PVDF/PI was 0.36 W/mK.Comparing with the uncomposite PI,thermal conductivity increased by 56.5%.(3)We chose the insulating boron nitride as the filler.Meanwhile,using the mechanical advantages of polyimide fiber,and the thermal conductivity network is built inside the polyimide textile to improve the thermal conductivity of the composite.Boron nitride/polyaryl ether ketone/polyimide textile composites(BN/PEK-C/PI)were prepared by impregnation-hot pressing process.Compared with BN/PEK-C composites,BN/PEK-C/PI textile composites had outstanding mechanical properties.Compared with 40% BN/PEK-C,the tensile strength of the composites(40-15-PEK-C-PI)which obtained by impregnating 40% BN/PEK-C polyimide textile with a solid content of 15% increased by 138%.BN/PEK-C/PI textile composites had excellent thermal conductivity.The composites(60-20-PEK-C-PI)which obtained by impregnation 60% BN/PEK-C polyimide textile with a solid content of 20% had the highest thermal conductivity,which is 496% higher than the PI without recombination.the Agari model showed that the preparation of composites with the slurry of high BN content was more conducive to the formation of thermal conduction pathways.(4)We removed the polyimide textile and oriented the boron nitride in the boron nitride/poly(aryl ether ketone)composites(BN/PEK-C)by hot-pressing technology.BN/PEK-C composites were prepared by solution method.Hot-pressing induced orientation is beneficial to improve the mechanical properties of BN/PEK-C composites.The tensile modulus and tensile strength of BN/PEK-C-HP composites were higher than those of BN/PEK-C composites after hot-pressing induced orientation.BN/PEKC-HP composites exhibited excellent thermal conductivity,which was anisotropic.The thermal conductivity in the in-plane direction enhanced more obvious,and the thermal conductivity of 60% BN/PEK-C-HP composite is 3.74 W/mK,which is 33 times higher than that of PEK-C.And the calculated thermal conductivity values obtained by the derived thermal conductivity model were consistent with the experimental values.The orientation of boron nitride in boron nitride/polyarryl ether ketone composites by hotpressing technology can effectively modify the arrangement of boron nitride and then enhance the thermal conductivity of the composites.It opens up a new idea for the practicalization of anisotropic special polymer-based thermal conductivity composites.