## 3 Experimental Results and Discussion  
### Mechanical Properties and the Permolecular Structure  
The physical and mechanical properties of neat UHMWPE and the UHMWPE-based composites, including those determined by tensile testing (Figure 2), are shown in Tables 1-4. It follows from Table 1 that loading UHMWPE with wollastonite in the studied content range caused an improvement  
The wollastonite functionalization with the \"KH-550\" coupling agent did not result in a notable increase in the mechanical properties of the composites relative to those with untreated fibers. However, yield strength was improved by 9% (Table 2). In addition, elongation at break and impact toughness significantly decreased, but only for the composite with a high wollastonite content (23 wt. %). Tensile and yield strength as well as elastic modulus of the composites functionalized with the \"Penta-1006\" coupling agent were lower than those of the ones silanized with \"KH-550\" (Table 3) and were close to the values of these characteristics treated with \"OTS\" (Table 4). Thus, an analysis of the physical and mechanical properties of the UHMWPE-based composites loaded with wollastonite fibers (both untreated and silanized with the coupling agents) enabled to conclude that the high values were mainly due to the \"mechanical\" adhesion of the non-polar UHMWPE matrix to the filler, determined by its complex (needle) shape [42]. Additional chemical adhesion due to the functionalization of fibers with the studied coupling agents (\"KH-550\", \"Penta-1006\", and \"OTS\") to a lesser extent affected the possibility of improving the mechanical properties of the composites at all filler contents. The permeacular structure of the investigated composites testified in favor of the foregoing (Figure 3). \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Filler Composition, wt. \%** & **Density** & **Shore (D)** & **Elastic Modulus** & **Yield Strength** & **Tensile Strength** & **Elongation at Break** & **Impact Toughness** \\
**7\%** & **(\(\rho\)), g-cm\({}^{-3}\)** & **Hardness** & **(G), MPa** & **(\(\sigma_{\
u}\)), MPa** & **(\(\sigma_{\
u}\)), \%** & **(\(a\)), kJ-m\({}^{-2}\)** \\ \hline None & 0.934 & 57.5 \(\pm\) 0.1 & 711 \(\pm\) 40 & 21.6 \(\pm\) 0.6 & 42.9 \(\pm\) 3.1 & 485 \(\pm\) 28 & 151 \(\pm\) 6 \\
7\% wollastonite + \"OTS\" & 0.979 & 57.2 \(\pm\) 0.2 & 849 \(\pm\) 41 & 22.1 \(\pm\) 0.3 & 38.0 \(\pm\) 3.1 & 422 \(\pm\) 16 & 120 \(\pm\) 4 \\
15\% wollastonite + \"OTS\" & 1.034 & 59.9 \(\pm\) 0.2 & 946 \(\pm\) 85 & 22.4 \(\pm\) 0.5 & 37.5 \(\pm\) 1.0 & 420 \(\pm\) 25 & 119 \(\pm\) 7 \\
23\% wollastonite + \"OTS\" & 1.102 & 60.2 \(\pm\) 0.3 & 1078 \(\pm\) 109 & 22.5 \(\pm\) 0.4 & 31.5 \(\pm\) 1.0 & 349 \(\pm\) 14 & 89 \(\pm\) 8 \\ \hline \end{tabular}
\end{table} 
Table 4: The physico-mechanical properties of the neat UHMWPE and the UHMWPE-based composites silanized with the “OTS” coupling agent. \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Filler Composition, wt. \%** & **Density** & **Shore (D)** & **Elastic Modulus** & **Yield Strength** & **Tensile Strength** & **Elongation at Break** & **Impact Toughness** \\
**7\%** & **(\(\rho\)), g-cm\({}^{-3}\)** & **Hardness** & **(G), MPa** & **(\(\sigma_{\
u}\)), MPa** & **(\(\sigma_{\
u}\)), \%** & **(\(a\)), kJ-m\({}^{-2}\)** \\ \hline None & 0.934 & 57.5 \(\pm\) 0.1 & 711 \(\pm\) 40 & 21.6 \(\pm\) 0.6 & 42.9 \(\pm\) 3.1 & 485 \(\pm\) 28 & 151 \(\pm\) 6 \\
7\% wollastonite + \"Penta-1006\" & 0.973 & 57.8 \(\pm\) 0.2 & 901 \(\pm\) 27 & 22.7 \(\pm\) 0.2 & 38.0 \(\pm\) 2.2 & 410 \(\pm\) 32 & 124 \(\pm\) 12 \\
15\% wollastonite + \"Penta-1006\" & 1.035 & 59 \(\pm\) 0.4 & 977 \(\pm\) 59 & 22.9 \(\pm\) 0.4 & 35.9 \(\pm\) 2.2 & 378 \(\pm\) 36 & 114 \(\pm\) 10 \\
23\% wollastonite + \"Penta-1006\" & 1.100 & 60.3 \(\pm\) 0.5 & 1102 \(\pm\) 96 & 24.4 \(\pm\) 0.3 & 33.4 \(\pm\) 6.3 & 322 \(\pm\) 32 & 89 \(\pm\) 7 \\ \hline \end{tabular}
\end{table}