# Formation of Conductive Networks in Polysulfone Filled with Graphite-Derived Materials
## 3 Results and Discussion
### Electrical Conductivity  
The mechanical properties and electrical conductivity of composite materials are generally influenced by the conductive filler's dispersion, shape, and orientation in an insulating polymer base matrix. Because the size of filler particles usually is several micrometers, a relatively high content of filler is usually required to achieve the threshold percolation value. A high filler concentration might result in poor mechanical characteristics and the use of unnecessary materials.  
Table 2 shows the PSU composite filled with NG and AG electrical conductivity depending on filler content. Electrical conductivity rises continuously at any degree of loading concentration. For 30 and 70% wt. %, NG's electrical conductivity spans from 0.0305 S/cm to 52.9 S/cm, whereas filling up to 70 wt. % with AG allows to reach only the magnitudes of 3.8 S/cm. Such a difference is associated with the formation of conducting networks and the well-distributed NG sheets inside the polymer. As a result, it  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Filler Content wt. \%** & & **Flexural Strength** & **Elastic Modulus** \\ \hline
**CB** & **NG** & **AG** & **MPa** & **GPa** \\ \hline
0 & 0 & 0 & 124 & 2.9 \\ \hline
2 & - & - & 49.9 & 2.26 \\ \hline
4 & - & - & 51.4 & 2.37 \\ \hline
6 & - & - & 32.6 & 1.84 \\ \hline
8 & - & - & 21.2 & 1.30 \\ \hline - & 30 & - & 17.4 & 5.80 \\ \hline - & 70 & - & 11.8 & 9.60 \\ \hline - & - & 30 & 38.7 & 4.20 \\ \hline - & - & 70 & 29.2 & 4.90 \\ \hline
2 & 28 & - & 23.7 & 4.18 \\ \hline
2 & - & 28 & 46.3 & 3.50 \\ \hline
4 & 26 & - & 26.7 & 5.34 \\ \hline
4 & - & 26 & 45.2 & 3.50 \\ \hline
2 & 68 & - & 15.4 & 8.70 \\ \hline
2 & - & 68 & 23.5 & 6.50 \\ \hline
4 & 66 & - & 10.9 & 7.80 \\ \hline
4 & - & 66 & 24.2 & 8.10 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Flexural strength of PSU-based composites filled with NG, AG, and CB.  
is evident that conductivity is affected by factors such as the filler content of the composite and how much of it is absorbed into the matrix. The huge graphite flakes in case of the NG filler made up the composite showed the lowest resistance at all concentration in comparison with the small flake filler of AG. Because the grain and crystallite sizes impact the electrical conductivity of carbon composites, large flake filler composites display superior conductivity, as predicted.  
Carbon black is known for its high electrical conductivity, which makes it a desirable filler material for improving the thermal and electrical properties of composites. When incorporated into a polysulfone-based composite, CB particles can enhance the composite's thermal and electrical conductivity by creating pathways for heat and electrical transfer. From the result we can see that the higher concentrations of CB will often enhance the electrical conductivity of the composite. This is because the greater abundance of CB particles allows for more effective material conduction. However, it is crucial to remember that there may be a threshold of diminishing returns where more CB additions will no longer significantly improve thermal conductivity. The result of the thermal and electrical conductivity of the composite filled with CB are shown in Table 5.  
To see the effect of using hybrid fillers in composite materials on the electrical conductivity, we measured the electrical conductivity of the composite filled with CB + NG and CB + AG with different filler contents, and the result are shown in Table 3.  
In the case of using CB + NG as fillers, we can see that the electrical conductivity of the composite increased 2 times while using 30 wt. % CB + NG) as fillers. In the case of using 70 wt. % (CB + NG) we can see the enhancement was not that great, due to the decrease in the content of NG in the matrix and the effect of CB, which was well dispersed in the matrix. In the case of using CB + AG as fillers, we did not see an enhancement in electrical conductivity due to the decrease in AG content in the composite.