## 4 Results and Discussion
### Influence of Plasma-Treated SiO\({}_{2}\) Nanofilers on Silicone-Rubber Nanocomite
#### 4.2.1 Electrical Tree Parameters
The growth rate of the treeing after initiation for unfilled SiR was faster than for the SiR nanocomposites. The growth rate of electrical treing in unfilled SiR was 11.60 \(\upmu\)m/s, while the growth rates of electrical treeing in DMNC were 2.66, 2.38, and 1.52 \(\upmu\)m/s for 1, 3, and 5 wt %, respectively. For STNC, the growth rates were 2.23, 1.76, and 1.08 \(\upmu\)m/s. PTNC showed the slowest growth rates, of 1.38, 0.84, and 0.63 \(\upmu\)m/s for 1, 3, and 5 wt %, respectively. From the results, it is clear that the growth rate of the electrical tree decreased with an increase in nanofiller loading; the decrease was significant in 1 wt % growth-rate nanocomposites compared to unfilled SiR. This result agrees with that of [PERSON] et al. [18], who found that small amounts of nanofiller (1 wt %) exhibited a slow propagation time, which resulted in slow growth rates compared to unfilled samples. In addition, from this result, it can be seen PTNC showed the slowest growth rate compared to that of DMNC and STNC. The higher filler concentration in PTNC resulted in excellent tree resistance. Figure 9 shows the average tree bridging time (T\({}_{\text{b}}\)) for DMNC, STNC, and PTNC with different nanofiller loadings. T\({}_{\text{b}}\) is the time taken for the tree to reach the ground electrode, which in our study was at 2000 \(\upmu\)m from the high-voltage electrode. The error bar represents the maximum and minimum values of T\({}_{\text{b}}\), while the center box represents the average value of T\({}_{\text{b}}\). Statistical analysis was done using ANOVA analysis and this confirmed that only the plasma treatment significantly improved the tree bridging time; silane treatment was marginal at best. Figure 8: Growth rates for DMNC, STNC, and PTNC. Figure 9: Tree bridging times for DMNC, STNC, and PTNC. From Figure 9, the unfilled SiR recorded the shortest T\({}_{\rm b}\) result, followed by DMNC, STNC, and PTNC. The average T\({}_{\rm b}\) of the unfilled SiR was 211.20 s, while the T\({}_{\rm b}\) for DMNC were 578.42, 867.35, and 1365.48 s for 1, 3, and 5 wt %, respectively; the T\({}_{\rm b}\) for STNC were 729.82, 979.82, and 1573.18 s for the same three wt %, respectively. PTNC showed the longest T\({}_{\rm b}\) of 1190.42, 1675.30, and 2326.28 s for 1, 3, and 5 wt %, respectively. From these results, it is clear that the T\({}_{\rm b}\) of electrical treeing increased with an increase in nanofiller loading. PTNC showed the longest T\({}_{\rm b}\) when compared to DMNC and STNC. The result shows that the tree bridging time of the nanocomposites is also dependent on both the condition of the treatment and the nanofiller loading. Nanocomposites with nanofiller take a longer time to break down compared to unfilled SiR. In addition, the T\({}_{\rm b}\) increased with an increase in nanofiller concentration. Overall, this result showed that PTNC has a longer breakdown time than the other nanocomposites. This result agrees with that of [PERSON] et al. [9], who found that plasma-treated nanocomposites had higher breakdown strength and longer endurance under constant electrical stress. 2.2 FESEM Analysis of the Silicone-Rubber Nanocomposites Filled with Plasma-Treated SiO\({}_{2}\) Nanoparticles  
In our study, the dispersion of the various treated SiO\({}_{2}\) nanof fillers to the polymer nanocomposite was analyzed using FESEM; FESEM analysis will show the agglomeration of the nanofillers, with diameters ranging from a few hundred nanometers to mere micrometers. The FESEM images of the DMNC-treated nanofiller (Figure 10a) showed that the nanofiller agglomerated and was not well dispersed in the polymer matrix, while clusters could be seen (Figure 10b) for the STNC-treated nanofiller. Dispersion greatly improved, however, with no obvious agglomerations appearing in the PTNC-treated nanofiller, as shown in Figure 10c. Figure 10: Field emission scanning electron microscopy (FESEM) images at 5 wt % for (**a**) DMNC; (**b**) STNC; and (**c**) PTNC.