L. A. Kornienko

Comparison of the efficiency of modification of SHMPE by nanofibers (C, Al2O3) and nanoparticles (Cu, SiO2) when obtaining antifriction composites

The effect of various nanofillers (nanofibers of Al2O3 and carbon, nanopowders of copper and SiO2) on the physico-mechanical and tribotechnical properties of superhigh-molecular polyethylene is investigated. It is determined that the modification of superhigh-molecular polyethylene by nanofibers and nanoparticles within the limits of 0.1–05 wt % results in a substantial rise in its deformation-strength characteristics and a multifold increase in its tribotechnical characteristics. By the methods of X-ray structure analysis, infrared spectroscopy, and electron microscopy, it is shown that modification of the polymer by the mentioned nanofillers results in the formation of an ordered (lamellar) permolecular structure. It is revealed that nanofibers form a stable film of friction transfer more quickly in comparison with nanoparticles. The optimum compositions of nanofillers, which determine the high wear resistance and the low constant of friction for polymer, are determined. The mechanical activation of the binder and filler powders provides a uniform distribution of the nanopowder within the binder and additionally enhances the physico-mechanical and tribotechnical properties of the composite.

Effect of mechanical activation of ultra-high-molecular-weight polyethylene on its mechanical and triboengineering properties

The effect of mechanical activation of initial ultra-high-molecular-weight polyethylene powders on the pysicomechanical properties of the polymer is studied. Mechanical activation is found to raise the strain and strength properties, as well as the triboengineering characteristics of ultra-high-molecular-weight polyethylene. X-ray diffraction analysis, IR spectroscopy, and optical and electronic microscopy show that mechanoactivation of the initial powder defines the polymer’s structural organization.

Wear resistance of composites based on ultrahigh molecular weight polyethylene filled with graphite and molybdenum disulfide microparticles

Tribological characteristics of ultrahigh-molecular-weight polyethylene (UHMWPE)-based compositions with graphite and molybdenum disulfide are studied under conditions of dry friction, boundary lubrication, and abrasive wear. It is shown that, under dry sliding friction, the wear rate of UHMWPE-graphite and UHMWPE-MoS2 polymer compositions is halved as compared to that of pure UHMWP, while their mechanical characteristics change only slightly. Under the conditions of abrasive wear, the wear resistance of these composites increases by 1.3–1.5 times. Concentrations of the fillers, which are optimum for improving the wear resistance, are determined. The supramolecular structure and the topography of worn surfaces of the UHMWPE compositions with various concentrations of the fillers are examined. A comparative analysis of the wear resistance of the composites under conditions of dry friction and lubrication is carried out. Mechanisms of the wear of the UHMWPE-graphite and UHMWPE-MoS2 polymer compositions under conditions of dry sliding friction and abrasive wear are discussed.

Wear resistance of composites based on hybrid UHMWPE–PTFE matrix: Mechanical and tribotechnical properties of the matrix

In order to develop biocompatible antifriction composites based on UHMWPE the mechanical and tribotechnical characteristics of a hybrid polymer matrix in the form of a mixture (blend) of UHMWPE with polytetrafluoroethylene (PTFE) have been studied under dry friction, boundary lubrication, and abrasive wear. It has been shown that the wear rate of the material under dry sliding friction was reduced more than twofold compared with pure UHMWPE. However, the mechanical characteristics have changed insignificantly. Under the boundary lubrication (distilled water), the wear resistance of the matrix material is similar to that for dry sliding friction. Under abrasive wear, the durability of the composites differs a little from that for pure UHMWPE. The mechanisms of wear of the polymer blend UHMWPE–PTFE under dry sliding friction and abrasive wear have been discussed.

Abrasive wear of micro- and nanocomposites based on super-high-molecular polyethylene (SHMPE). Part 1. Composites based on shmpe filled with microparticles AlO(OH) and Al2O3

The abrasive wear of pure SHMPE and its dispersed reinforced composites are studied when they are filled with AlO(OH) and Al2O3 microparticles. It is established that the abrasive resistance of the studied microcomposite can grow by up to 16–18 times compared to the original SHMPE in response to the abrasive grain size. Optic profilometry, IR-spectroscopy, differential scanning calorimetry, and scanning electron microscopy are employed to study the supramolecular structure and tribosurface of the studied anfrictional materials. It is shown that the abrasive resistance of the composites is governed by the nature and content of the microfiller and abrasive, and, to a greater extent, by the ratio of the size of the microfiller and abrasive grain. The abrasive resistance of the SHMPE-based microcomposites is discussed.

Antifrictional composites based on chemically modified UHMWPE. Part 2. The effect of nanofillers on the mechanical and triboengineering properties of chemically modified UHMWPE

The mechanical and tribological properties of nanocomposites based on chemically modified ultra-high molecular weight polyethylene are determined. The super-molecular and chemical structure of the nanocomposites based on the block copolymers UHMWPE-grafted UHMWPE and UHMWPE-grafted HDPE are studied by the methods of X-ray structural analysis, IR spectroscopy, scanning differential calorimetry, and electron microscopy. The mechanical and tribological properties of the nanocomposites based on the block copolymers are found to differ insignificantly from those of the nanocomposites on the base of non-modified UHMWPE. The crystallization and formation of super-molecular structure in the heterogeneous materials under study are shown to depend on the heterogeneity of the distribution of the nanofillers. The authors believe that chemical modification in terms of grafting polar monomers is unable to improve the adhesion of the nanofillers to the high-molecular matrix (UHMWPE). Thus, the wear resistance of the UHMWPE-based nanocomposites is mostly governed by the crystallization conditions and type of supermolecular structure formed during crystallization (either spherulitic or lamellar).

Comparative analysis of the influence of nano- and microfillers of oxidized Al on the frictional-mechanical characteristics of UHMWPE

The influence of nano- and microfillers, including nanofibers and powder of Al2O3 and aluminum oxyhydrides AlO(OH) on the mechanical and tribological characteristics of ultrahigh-molecular-weight polyethylene (UHMWPE) is studied. It is found that modification of UHMWPE with nanofibers of Al2O3 within 0.1–0.5 wt % ensures a considerable increase in its hardness and multifold increase in its wear resistance. Modification with ultradisperse powders of Al2O3 (200–500 nm) in the same amounts has an insignificant effect on the polymer characteristics. Filling of UHMWPE with micron-sized particles (3–50 μm) in amounts of 20 wt % results in increased wear resistance of the original polymer, comparable with the wear resistance at low nanofiber content. X-ray diffraction analysis, IR spectroscopy, and electron microscopy are used to show that incorporation of Al2O3 nanofibers into UHMWPE results in the formation of a fundamentally different supermolecular structure in comparison with the use of microfillers.

Antifriction nanocomposites based on chemically modified UHMWPE. Part 1. Mechanical and tribological properties of chemically modified UHMWPE

The mechanical and tribological properties of chemically modified UHMWPE are studied. X-ray diffraction analysis, IR spectroscopy, scanning differential calorimetry, and electron emission are used to study the permolecular structure and friction surface of polymers with different amounts of copolymers UHMWPE and LDPE grafted with maleic anhydride. Addition of grafted UHMWPE is shown to have no effect on the viscoelastic properties of the polymer-polymer composite, while the addition of grafted LDPE noticeably improves its performance (ductility, plasticity) while retaining its strength. Chemical modification of UHMWPE significantly improves its wear resistance (two to three times), which is due to the features of polymer crystallization and the formation of a permolecular structure.

Antifrictional nanocomposites based on chemically modified UHMWPE. Part 3. Comparison of modification effect of compatibilizers on mechanical and tribotechnical properties

Two compatibilizers-vinyltrimethoxysilane (VTMS) and maleic anhydride (SMA)—are subjected to comparative analysis in respect to their effect on the mechanical and tribological properties of the composites based on chemically modified UHMWPE. The methods of IR spectroscopy, scanning differential calorimetry, and electronic microscopy are used to study the supermolecular structure of nanocomposites on the base of UHMWPE block-copolymer + 10% UHMWPE-g-VTMS. The mechanical and tribotechnical properties of these nanocomposites are further compared to those of the nanocomposites based on UHMWPE + 10% HDPE-g-SMA. It is shown that the nanocomposites based on block-copolymers with the mentioned compatibilizers have similar (spherulitic) structure and roughly equal wear resistance, being close to those of the composites based on the non-modified polymer. The wear resistance of the nanocomposites on the base of UHMWPE depends on whether the fillers are present and distributed evenly in the matrix. This defines the crystallization conditions and, as a consequence, the type of the formed supermolecular structure.

Abrasive wear of micro- and nanocomposites based on ultra-high-molecular-weight polyethylene (UHMWPE): Part 2. composites based on UHMWPE filled by nanoparticles and nanofibers

The paper presents investigation results of nanocomposites based on ultra-high-molecular-weight polyethylene filled by Al2O3, C, Cu, SiO2 nanofillers. It is shown that nanofillers increase the abrasive resistance of ultra-high-molecular-weight polyethylene (at an abrasive graininess R240) to a much less extent (up to 55%) compared to microfillers. The structure and friction surfaces of ultra-high-molecular-weight polyethylene and its nanocomposites have been studied by optical profilometry and microscopy, IR spectroscopy, differential scanning calorimetry, and scanning electron microscopy. It has been proved that the abrasive wear resistance of the nanocomposites depends weakly on the filler type, but is defined by the matrix structure (crystallinity, ordering) and the abrasive graininess of the counterbody. The wear mechanisms of ultra-high-molecular-weight-polyethylene-based nanocomposites in the presence of abrasives were compared to the conditions of dry friction.