## 4 Discussion
Therefore, this order of increasing service life \(t\) of the MP bearings differs significantly from the above sequence of increased contact pressures \(p_{\max}\): PTFE \(\rightarrow\) RA6+MoS2 \(\rightarrow\) PA6+oil \(\rightarrow\) PA6 \(\rightarrow\) PET+20 PTFE \(\rightarrow\) PET \(\rightarrow\) PA6+30 GF \(\rightarrow\) PA6+30 CF \(\rightarrow\) PEEK+30 GF \(\rightarrow\) PEEK (Figures 2 and 3). According to the calculations carried out using the criterion of the calculated maximum life \(t_{max}\), the best MP bearings in each of the tested tribopolymer groups were PA6+MoS2 (polyamides), PTFE+15C+5 MoS2 (polytetrafluoroethylenes), PET+20 PTFE (polyethylene tetrephthalates), and PEEK+30 GF (polyetheretherketones). There are no computational methods similar to the one presented in the literature. A comparison of the pattern of change in \(p_{\max}\) in the bearings with different polymer bushings and the durability \(t\) of the bearings is shown in Figure 6. Here, it is easy to track the patterns of change in the contact pressure and service life of the bearings with different bushings. The Young's modulus \(E_{1}\) (Figure 7) and friction coefficients \(f\) in these hybrid tribo-conjugations of the polymers (Figure 8) have different sequences of change from the minimum to the maximum value. Therefore, the calculated durability \(t\) of a bearing depends on the complex effect of the maximum contact pressure \(p_{max}\), the wear resistance characteristics of polymeric materials (\(B_{1},m_{1},\) and \(\tau_{10}\)), [PERSON]'s modulus \(E_{1}\), and friction coefficient \(f\). All of these factors are included in Formula (4) for calculating the bearing's mechanical life. According to the criterion of maximum durability \(t\), bearings with a PET+20 PTFE bushing are optimal compared to the other groups of polymers with a bushing made of PA6+MoS2 or PA6+oil, PTFE+15C+5 MoS2, PET+20 PTFE, or PEEK+30 GF. The elastic Young's moduli of the studied polymeric materials, determined using the Oliver-Farr method, are shown in Figure 7.  
The Young's modulus of the investigated polymeric materials differed by a maximum of 4.29 times (PEEK+30 GF/PTFE+10C+10 GF). In the group of polyamides, the filling with CF and GF significantly increased the Young's modulus compared to the base PA6 (Table 1). Filling PA6 with oil reduced it, and MoS2 did not change it. In the polyetheretherketone, a PTFE filling had a slight reducing effect on the modulus, and in polyethylene terephthalate, a GF filling slightly increased it (Tables 2 and 3). In all the groups of polymers, fillers changed the Poisson's ratio slightly compared to the base materials (Tables 1 and 3). Figure 8 shows the experimentally determined sliding friction coefficients necessary to evaluate the life of MP bearings at the calculated contact pressures \(p_{max}\) (Figures 2 and 3). The dry friction coefficients depend not only on the type of base polymer but also on the type of filler. The introduction of fiberglass into the base polymer increases the coefficient of friction of composites under dry friction on steel 45. Instead, the fillers with MoS2, oil, and PTFE as lubricants have little effect on it. The increase in load and contact pressures causes a decrease in the coefficient of friction. This effect is reported in the literature. According to the well-known and thoroughly experimentally verified molecular-mechanical theory of sliding friction of rough bodies developed by [PERSON], the total coefficient of friction is the sum of the adhesive (molecular) and deformational (mechanical) components. At low loads to the tribological system, the mechanical component of friction caused by the deformation of micro-irregularities of the contacting surfaces dominates. It decreases with increasing load, while the adhesion of the surface layers plays a greater role. Correspondingly, changing the role of both of these friction mechanisms causes a decrease in the coefficient of friction.