| Graphene possesses a high thermal conductivity, which appropriates for enhancing the heat transfer performance of polymer materials. However, the agglomeration and sedimentation of graphene result in a poor distribute in the polymer matrix. On the other hand, the modified graphene oxide has a good compatibility with polymer material, but its intrinsic thermal conductivity is low due to the defect on the graphene surface. In order to resolve this contradiction, the high viscosity polyimide was employed to mix with graphene to prepare graphene/polyimide composite by using Speed Mixer, which is suitable for high viscosity operation and has excellent mixing effect depending on its high speed. Moreover, the three-dimensional graphene was synthesized to avoid the horizontal orientation of graphene in the polyimide matrix with the direct blending method. Then, the polyimide was infused into the void of the three-dimensional to prepare the graphene/polyimide composite. In this study, the raw graphene and the as-prepared three-dimensional were characterized detailed. Simultaneously, the thermal conductivity, thermal stability and other properties of as-prepared graphene/polyimide composites were investigate.In the direct blending method, the thermal conductivity of polyimide composites were significantly improved by incorporation of graphene sheets, which has a positive correlation with the graphene loading. The thermal diffusivity of polyimide had increased by 47.6% with only 1 wt% graphene loading. When the concentration of graphene reaches 11.0 wt%, the thermal conductivity of the composite sample achieves 1.002 W/m K, which is ab out 3 times increase compared with the neat PI(0.254W/m K).The thermal stability(Td-10%, the 10% decomposition temperature) of PI composites were improved in the beginning and then decreased with the increase of GSs content. The maximum Td-10%value achieved 548.2 °C with the incorporation of 4.0 wt% graphene loading, corresponding to the increases by 6.9 °C. However, in the 11.0wt% graphene loading, Td-10%of polyimide composite decreased to 539.5 °C. The modulus is enhanced with the addition of graphene content increasing. When the addition 11.0 wt%, the maximum modulus value is up to 4.04 GPa, which is 100% increase when compared with the neat PI(2.01 GPa).Meanwhile, the tensile strength of the PI composites increased with the increase of GSs content up to 0.5 wt%, then decreased with the increase of GSs content. The maximum value of tensile strength of the PI composites achieved 98.5 MPa with the incorporation of 0.5 wt%. Furthermore, the elongation of the PI composites also increased with the increase of GSs content up to 0.1 wt%, then decreased with the increase of GSs content. The maximum value of elongation of the PI composites achieved 28.9% with the incorporation of 0.1 wt% GSs.. The thermal conductivity of PI/3DSG composites with 11 wt% filler addition can be up to 2.63 W/m K, approximately a ten-fold enhancement in comparison with that of neat PI. Furthermore, the 3DSG shows a better synergistic effect in thermal conductivity improvement by 182% relative to simple mixture of Si C nanowires and GSs fillers with the same additive content. The reinforced thermal transfer properties can be attributed to the formation of efficient heat conduction pathways among PI matrix. The thermal stability of PI composites were also improved by incorporation of 3DSG. When the filler hybridized by Si C nanowires and GSs was adopted, the Td-5wt% value achieved 531.4 °C, with the increases by 1 5.9 °C. |
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