# Mechanical and Conductive Behavior of Graphite Filled Polysulfone-Based Composites
## 3 Results and Discussion
### Composite Density and Porosity  
To study the effect of increasing filler content on the composites' density, we have measured the density of the composite by hydrostatic methods. Table 2 shows the density of the measured samples in this work compared to the composite density we obtained in the previous work. Here we measured the density of  
Figure 1: SEM micrographs of: polysulfone (PSU) + 30 wt.% NG (**a**); PSU + 30 wt.% AG (**b**); PSU + 30 wt.% EG (**c**); PSU + 70 wt.% NG (**d**); PSU + 70 wt.% AG (**e**); PSU + 70 wt.% EG (**f**) \(\times\)500.  
samples obtained, as was mentioned above, by consolidation using a steel mold with holes (column 1) and using a steel frame (column 2), used for consolidation of samples as described in paper [32]. We can see how the density increased as the filler content was getting higher for NG and AG. For EG we noticed that the density of the sample varied as the filler content increased due to the structural defects in the EG. By comparing the current results to the earlier ones [32], we can conclude that the change in sample preparation technology that increased density allowed for higher thermal conductivity values and higher electrical conductivity in the composites. Graphite particles, when introduced into the matrix, form agglomerates randomly distributed in it, which affects the observed properties. The mechanisms of structural change with an increase in the degree of filling are shown in Figure 2. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Filler Content wt.\%**} & \multicolumn{5}{c}{**Density g/cm\({}^{3}\)**} \\ \cline{2-7}  & \multicolumn{2}{c}{**NG**} & \multicolumn{2}{c}{**AG**} & \multicolumn{2}{c}{**EG**} \\ \cline{2-7}  & **1** & **2** & **1** & **2** & **1** & **2** \\ \hline
30 & 1.42 \(\pm\) 0.3 & 1.37 \(\pm\) 0.25 & 1.40 \(\pm\) 0.3 & 1.69 \(\pm\) 0.44 & 1.34 \(\pm\) 0.23 & 1.22 \(\pm\) 0.16 \\
40 & 1.47 \(\pm\) 0.32 & 1.46 \(\pm\) 0.32 & 1.46 \(\pm\) 0.32 & 1.59 \(\pm\) 0.42 & 1.38 \(\pm\) 0.25 & 0.97 \(\pm\) 0.11 \\
50 & 1.53 \(\pm\) 0.35 & 1.51 \(\pm\) 0.31 & 1.52 \(\pm\) 0.35 & 1.46 \(\pm\) 0.32 & 1.3 \(\pm\) 0.23 & 0.95 \(\pm\) 0.12 \\
60 & 1.54 \(\pm\) 0.37 & 1.49 \(\pm\) 0.3 & 1.56 \(\pm\) 0.38 & 1.45 \(\pm\) 0.32 & 1.51 \(\pm\) 0.35 & 0.92 \(\pm\) 0.1 \\
70 & 1.59 \(\pm\) 0.38 & 1.59 \(\pm\) 0.38 & 1.57 \(\pm\) 0.37 & 1.46 \(\pm\) 0.32 & 1.54 \(\pm\) 0.32 & 0.89 \(\pm\) 0.05 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Density of PSU based composites filled with NG, AG and EG. Figure 2: The changes in a composite’s form as the filler content is increased. With an increase in the filler content for NG particles having a lamellar shape, with an increase in the degree of filling, the degree of orientation of the particles in the material increases and the number of contact pads through which heat or charges are transferred increases. With AG filler, point connections exist, and as the degree of filling grows and agglomerates are broken down, their density rises, increasing the network of filler particles' conductivity as their concentration rises. However, this increase is significantly lower than in the case of natural graphite because of the point type of the connections between the particles of AG. All of the graphite fillers we used have internal defects that have an impact on their thermal and electrical characteristics. The porosity of this filler is greater than that of NG or AG in the situation of EG, when incomplete separation of the resultant flakes occurs during intercalation. As a result, the density does not significantly rise with an increase in filling up to 50 wt.% (Figure 3). In the process of mixing, particle agglomerates start to break down and the dispersion of existing particles into individual graphite flakes improves when the EG content rises above 50 wt.%, which causes a large increase in the viscosity of the polymer solution and an increase in shear stresses. The material's porosity starts to decrease as its density reaches that of NG and AG.