## 3 Results
### The Point Tribological Contact  
Table 3 presents the integral values of the tribological characteristics of the studied nanocomposites. After reinforcing PI with CCFs, its CoF value decreased by 8%, while subsequent loading with both types of nanotubes (CNTs and HNTs) was accompanied by only a slight increase. For the PEI-based nanocomposite, filling with HNTs lowered the CoF level by 8% compared to that of the neat polymer. Figure 3 shows the variation kinetics of the CoF values for all the studied materials. In the PI case (Figure 3a), both PI/10 CCF and PI/10 CCF/1 CNT were characterized by noticeable CoF oscillations, which differed from the PI/10 CCF/1 HNT sample. However, the high CoF value, comparable to that of neat PI, did not enable us to position them as antifriction ones. For neat PEI, the CoF value of ~0.3 was not significantly lower than  
Figure 2: SEM micrographs of the structures of the neat PI (**a**), neat PEI (**b**), PEI/10 CCF/1 HNT (**c**) and PEI/10 CCF/1 CNT (**d**) nanocomposites. that of ~0.39 obtained for neat PI. On the other hand, the CoF variation kinetics for the PEI/10 CCF/1 HNT nanocomposite were not accompanied by any pronounced oscillation at its minimum average level of ~0.24. A comparison of the CoF and WR values (Table 3) enabled the following conclusions:  
* The WR value for neat PEI was three times greater than obtained for neat PI (although the CoF level was higher by ~0.1 for neat PI);
* Reinforcing PI with CCFs lowered the WR value of the PI/10 CCF nanocomposite by 4.8 times, and its additional modification with nanofillers only slightly improved wear resistance (by 9-12%);
* After reinforcing PEI with CCFs, its WR level decreased by ~13 times compared with that of the neat polymer, while subsequent modification with CNTs additionally reduced it by ~1.5 times, while such an improvement was much higher (~6 times) in the HNTs case. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & **Filler** & **Density \(\rho\),** & **Shore \(D\)** & **Elastic** & **Ultimate Tensile** & **Elongation at** \\  & **Composition** & **(g/cm\({}^{3}\))** & **Hardness** & **(GPa)** & **(MPa)** & **(MPa)** & **Break \(\epsilon\) (\%)** \\ \hline \multirow{3}{*}{1} & PI/PEI & 1.37/ & 80.2\(\pm\) 0.8/ & 2.60 \(\pm\) 0.69/ & 110.7 \(\pm\) 1/ & 13 \(\pm\) 0.7/ \\  & PI/PEI & 1.26 & 79.9 \(\pm\) 0.3 & 3.12 \(\pm\) 0.15 & 123.1 \(\pm\) 0.5 & 16.1 \(\pm\) 1.2 \\  & PI/10 CCF & 1.42/ & 80.6 \(\pm\) 0.4/ & 6.40 \(\pm\) 0.33/ & 152.1 \(\pm\) 6.4/ & 5.9 \(\pm\) 0.3/ \\  & PEI/10 CCF & 1.31 & 81.4 \(\pm\) 0.3 & 6.54 \(\pm\) 0.43 & 153.2 \(\pm\) 12.5 & 3.7 \(\pm\) 0.6 \\  & PI/10 CCF/1 CNT & 1.4/ & 80.9 \(\pm\) 0.64/ & 6.04 \(\pm\) 0.15/ & 115.5 \(\pm\) 5.4/ & 3.1 \(\pm\) 0.2/ \\  & PEI/10 CCF/1 CNT & 1.32 & 81.3 \(\pm\) 1.1 & 5.59 \(\pm\) 0.05 & 118.8 \(\pm\) 4.7 & 3.4 \(\pm\) 0.2 \\  & PI/10 CCF/1 HNT & 1.39/ & 81.0 \(\pm\) 0.5/ & 5.94 \(\pm\) 0.21/ & 121.5 \(\pm\) 4.7/ & 3.4 \(\pm\) 0.2/ \\  & PEI/10 CCF/1 HNT & 1.31 & 81.9 \(\pm\) 1.0 & 6.03 \(\pm\) 0.17 & 127.0 \(\pm\) 1.4 & 3.7 \(\pm\) 0.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The physical and mechanical properties of neat PI and PEI, as well as the PI- and PEI-based nanocomposites. Figure 3: The time dependence of the CoF values for the PI- (**a**) and PEI-based (**b**) nanocomposites. Point tribological contact. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**No.**} & **Composition (wt.\%)** & **Coefficient of Friction, CoF** & **Wear Rate, WR, mm\({}^{3}\)/N- m, 10\({}^{-6}\)** \\ \hline
1 & PI/PEI & 0.388 \(\pm\) 0.012/0.297 \(\pm\) 0.026 & 134.16 \(\pm\) 18.50/390.21 \(\pm\) 20.51 \\
2 & PI/10 CCF/PEI/10 CCF & 0.304 \(\pm\) 0.036/0.286 \(\pm\) 0.018 & 27.86 \(\pm\) 3.42/30.39 \(\pm\) 2.68 \\
3 & PI/10 CCF/1 CNT/PEI/10 CCF/1 CNT & 0.320 \(\pm\) 0.030/0.295 \(\pm\) 0.017 & 29.20 \(\pm\) 3.27/21.28 \(\pm\) 2.15 \\
4 & PI/10 CCF/1 HNT/PEI/10 CCF/1 HNT & 0.331 \(\pm\) 0.020/0.241 \(\pm\) 0.012 & 31.95 \(\pm\) 2.86/5.37 \(\pm\) 0.59 \\ \hline \hline \end{tabular}
\end{table}