## 4 Results and Discussion
### Analysis of Influencing Factors on Resistivity
#### 4.1.2 Extrusion Temperature, Speed and Flow Rate  
Figure 9 shows the examined influencing factors on resistivity for PPC structured by raster angle orientation. It can generally be seen that, besides the raster angle, the extrusion temperature strongly influences the resulting resistivity. Thus, the higher energy input probably results in both a lower inner-bead porosity and inter-bead porosity due to the molecular diffusion of the polymer chains within the interface zone between the strands [31; 32]. The grown interface zone (neck) leads to a lower resistivity. In general, this effect is lower for a raster angle of 0\({}^{\circ}\) most likely due to less inner-bead porosity and for the infill pattern of \(\pm\)45\({}^{\circ}\) probably due to a higher inter-bead porosity because of an intersecting of the extruded strands. Furthermore, lower speeds also result in lower resistivity due to a higher energy input and probably a higher accuracy and, thus, less porosity. However, a detailed analysis of the influence of the parameters regarding porosity, and thus resistivity, was not conducted and has to be done in further experimental investigations. It has to be noted that, because of the turnaround points for the raster angles of \(\pm\)45\({}^{\circ}\) and 90\({}^{\circ}\), the maximum speeds of 40 mm/s and 60 mm/s were likely not reached due to the machine's acceleration. The resistivity is also influenced by means of a variation of the flow rate. By using a raster angle of 90\({}^{\circ}\), an underextrusion (flow rate  
Figure 8: Bar plots of the mean value of the resistivity for selected specimens with standard deviation each of PPC, 3 dk, FFE, and M3D with the different raster angle orientations. of 95%) results in a slightly increased resistivity, whereas at 0\({}^{\circ}\) and \(\pm\)45\({}^{\circ}\) no clear tendencies are visible. The statistical outliers for a raster angle of 0\({}^{\circ}\) and a flow rate of 100% cannot be explained now and require additional subsequent investigations. In general, the resistivity of 3 dk is significantly higher than of PPC, even though the filler is identical. This probably results from a difference in filler content and defects in the filament strand that occur as a result of the pressure of the feed mechanism. The resulting defects that occurred in the filament strand after extrusion are shown in Figure 10. Consequently, voids inside, along and between the beads exist and, thus, the electrical resistance increases due to the higher porosity. Both a high extrusion temperature and to a lesser extent a low speed positively influence the resistivity due to a higher energy input that results in smaller inner-bead and inter-bead voids (see Figure 11). In comparison to that, the influence of flow rate and raster angle are rather low because of defects in the filament strand. Figure 11: Dependencies of the resistivity of 3 dk regarding temperature, extrusion speed and flow rate structured by raster angle. Figure 9: Dependencies of the resistivity of PPC regarding temperature, extrusion speed and flow rate structured by raster angle. Because of the different filler (CNTs), the FFE shows a significant lower resistivity than the two CB filled materials. An overview of the dependencies of the resistivity is represented in Figure 12. Overall, raster angle orientation has the greatest influence on resistivity followed by extrusion temperature except for raster angle 0\({}^{\circ}\). It is assumed that the effect of an orientation of the carbon nanotubes along the extrusion direction mainly determines the resistivity for the raster angle orientation of 0\({}^{\circ}\) and, as a result from this, the temperature has hardly any influence. The lower resistivity of the batches with the process parameter sets of a temperature of 220 \({}^{\circ}\)C, a flow rate of 100%, and speeds of 40 or 60 mm/s is probably due to the higher shear forces, which can be transmitted by the higher viscosity of the melt.