## 1 Introduction  
Currently, one of the common antifriction structural polymeric materials possessing improved strength properties and high chemical resistance in a wide range of operating temperatures (primarilysubzero) is ultra-high molecular weight polyethylene (UHMWPE) [1; 2; 3; 4]. Its high physical and mechanical characteristics are determined by the structure of macromolecules. During solidification from a melt, all UHMWPE elements are interconnected by transition macromolecules to one extent or another [1; 5]. Due to its unique set of properties, UHMWPE is applied in many areas where conventional polymer grades do not withstand severe operating conditions. In addition, UHMWPE is being replaced metals in some applications and used as the only suitable material. Since the 1960s, UHMWPE has remained the most widely applied material in medicine as a component of joint endoprostheses [6; 7; 8]. In various engineering industries, UHMWPE is implemented for the manufacture of bearings, slotted and mechanical seals, as well as hydroheel discs and lightweight corrosion-resistant impellers. The use of UHMWPE as feed bearings with water lubrication in shipbuilding is expanding because of the requirement to solve the problem of the marine environment pollution with lubricating oil from sea vessels [6; 7; 8; 9; 10; 11]. The main factor determining the high wear resistance of UHMWPE is its supermolecular structure. It has been found in [12; 13; 14; 15; 16] that reorientation of macromolecules occurs in the surface layer along the sliding direction due to the development of deformation processes caused by contact with a counterpart. This molecular reorganization process forms a structure on the friction surface oriented along the sliding direction. It also means that loading with fillers of various materials and sizes affects wear resistance, including due to changing the process nature. It is known that neat UHMWPE wears out significantly during continuous operations, especially in dry friction conditions. Its use in extensively loaded friction units, products, and lining plates is limited by the low melting temperature, elastic modulus, and strength [17]. However, there are many ways to improve wear resistance of UHMWPE-based composites. One of the widely applied industrial methods for modifying UHMWPE is the crosslinking of macromolecules [18; 19; 20]. Nevertheless, the polymer composites can be oxidized, since not all free radicals are mobile enough to recombine with each other [21]. The UHMWPE-based nanocomposites are characterized by increased wear resistance and the low friction coefficient compared to those of neat UHMWPE [22; 23]. However, the use of nanoparticles as a filler for UHMWPE is accompanied by a number of limitations, such as high costs of nanofillers, the complexity of the homogeneous nanofiller distribution in the polymer matrix, insufficient mechanical properties of the nanocomposites, their high wear rate under severe loading conditions, etc. In addition, UHMWPE cannot be processed by methods typical for most thermoplastics due to its high molecular weight. Also, it does not interact with other materials and fillers (both organic and inorganic). In this regard, enhancing adhesion between the filler and the UHMWPE matrix is an urgent task. To date, a rather large number of studies [24; 25; 26; 27; 28; 29] has been devoted to its solution. For example, investigations of the UHMWPE-based composites containing chopped carbon fibers in amounts of up to 12 wt. % have been carried out in [24]. As a result of annealing in air at a temperature of 500 \({}^{\circ}\)C, an effective structure has been formed on fibers and their surface activity has been increased. Loading UHMWPE with untreated carbon fibers has increased the elastic modulus from 0.75 up to 1.54 GPa (with their content of 10 wt. %). In the case of preliminary thermal oxidation of fibers, the elastic modulus has reached 1.56 GPa with their content of 2 wt.