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In order to design high-strength solid-lubricant composites for applications in friction units, the mechanical and tribological properties of polyimide (PI) based composites reinforced with long annealed carbon fibers and filled with commercially available solid-lubricant fillers of various nature (10 wt % PTFE, Gr, MoS2) under the conditions of metal-polymer and ceramic-polymer tribological mating were studied. It was shown that loading with long carbon fibers (CF) with the length of 2 mm and a content of 10 wt % increased the elastic modulus by 2.5 times, while the ultimate strength enlarged by 1.5 times. It was found that the highest wear resistance was characteristic for a three-component mixture composite with annealed CF and PTFE particles (in comparison with neat PI, the wear rate decreased by ∼419 times for metal-polymer and by ∼483 times for ceramic-polymer tribological couplings when tested by pin-on-disk scheme). Inorganic solid-lubricant fillers (Gr, MoS2) increased wear resistance of the composite by 35 (Gr) and 5 times (MoS2) for metal-polymer and ceramic-polymer mating, respectively. On the basis of a comparative analysis of various solid lubricant fillers some practical recommendations were given for the development of high-strength antifriction PI based composites for friction units using available reinforcing and solid lubricant fillers. [ABSTRACT FROM AUTHOR]

Friction and wear of polyetheretherketone (PEEK) was simulated taking into account the development of triboxidation and scuffing processes induced by the work of friction forces and plastic deformation. From the solid mechanics point of view, these effects were accounted in the form of friction coefficient variation. It took place when the temperature has exceeded a threshold value at the contact between a steel counterpart and a polymer sample (due to friction heating). Simulation of friction and wear processes was carried out by solving a contact and heat conduction problems for a computational domain. The latter corresponded to conditions of experimental wear tests conducted by "block-on-ring" scheme. The effect of friction coefficient variation at scuffing on volumetric wear rate of PEEK and PEEK-based carbon fiber reinforced composites has been established. The effect of carbon fiber length on wear resistance of PEEK-based composites was analyzed. It was shown that when scuffing is taken into account, the calculated value of wear intensity of PEEK-based composites increases. It was shown that loading with long carbon fibers ensured reduction of the wearing both without and with taking the scuffing effect into account. [ABSTRACT FROM AUTHOR]

Mechanical and tribotechnical characteristics of polymer-polymeric composites of UHMWPE are studied with the aim of developing extrudable, wear-resistant, self-lubricant polymer mixtures for Additive Manufacturing (AM). The motivation of the study is their further application as feedstocks for 3D printing. Blends of UHMWPE with graft- and block copolymers of low-density polyethylene (HDPE-g-VTMS, HDPE-g-SMA, HDPE-b-EVA), polypropylene (PP), block copolymers of polypropylene and polyamide with linear low density polyethylene (PP-b-LLDPE, PA-b-LLDPE), as well as cross-linked polyethylene (PEX-b), are examined. The choice of compatible polymer components for an ultrahigh molecular weight matrix for increasing processability (extrudability) is motivated by the search for commercially available and efficient additives aimed at developing wear-resistant extrudable polymer composites for additive manufacturing. The extrudability, mechanical properties and wear resistance of UHMWPE-based polymer-polymeric composites under sliding friction with different velocities and loads are studied. [ABSTRACT FROM AUTHOR]