# Formation of Conductive Networks in Polysulfone Filled with Graphite-Derived Materials
## 3 Results and Discussion
### Thermal Conductivity
As previously stated, CB enhances the viscosity of the composite material, and as shown in the SEM micrographs, the orientation of the NG sheets was improved and the sheets in the composite were more regular. As we can see in Figure 11, the forming efficient conductive paths using CB as a second filler with NG. Figure 12 shows the thermal conductivity of the PSU-based composite filled with NG and NG + CB measured along the sample plane. It should be noted that whereas in the previous paper [34], we reported the thermal conductivity magnitude measured along the direction of the pressure application at the  
Figure 11: Illustration of forming efficient conductive paths using CB as a second filler with NG. Pressure at consolidation was applied perpendicular to the sample plane. Figure 12: Thermal conductivity in the in-plane direction of PSU-based composites filled with 30 (1), 40 (2), 50 (3), 60 (4), and 70 (5) wt. % of NG **(a)**; NG + CD **(b)** 28 wt. % NG + 2 wt. % CB (1), 26 wt. % NG + 4 wt. % CB (2), 68 wt. % NG + 2 wt. % CB (3), 66 wt. % NG + 4 wt. % CB (4). samples' consolidation, in the present study we compared the thermal conductivity measured both along the direction of the pressure application at the samples' consolidation and in the direction normal to the pressure application direction. As is illustrated in Figure 11, flake-shape particles of NG are oriented along the sample plane, i.e., perpendicular to the pressure application direction. Comparing data presented in Figures 10 and 12, one should note that the thermal conductivity of the composite containing 70 wt. % NG measured normally to the sample plane was found to be of about 17 W/m\(\cdot\)K, whereas in the direction along sample plane the same composite exhibit thermal conductivity magnitude was about 27 W/m\(\cdot\)K. Addition of CB enhance the difference in the conductive between various direction, composite containing 66 wt. % of NG and 4 wt. % of CB possess thermal conductivity in the direction perpendicular to sample plane of about 10 W/m\(\cdot\)K, whereas thermal conductivity in the in-plane direction was found to be more than 37 W/m\(\cdot\)K. Moreover, comparing the curve 5 in Figure 12a with the curves 3 and 4 in Figure 12b, it should be concluded that addition of CB to composite filled with NG increased the thermal conductivity in the in-plane direction significantly. It should be noted that such an increase was found only for highly filled composites; for composites with filler content of 30 wt. %, the addition of CB provided no positive effect, as can be seen by comparing the curve 1 in Figure 12a with the curves 1 and 2 in Figure 12b. Tables 2 and 3 collect the experimental results of thermal conductivity measurements. It is seen that for all the NG-containing samples, thermal conductivity in the in-plane direction, i.e., along the NG flakes' orientation, is higher than in the direction normal to the sample plane. It should be noted that composites filled with AG measurements do not show any difference between thermal conductivity in various directions. It is evidently because of the near-spherical shape of AG particles, so detailed measurements of in-plane thermal conductivity for this filler were not provided.