A. A. Shepelevskii

Antiwear Effect of Fullerene C60 Additives to Lubricating Oils

The protective film (≤1000 Å thick) formed on the copper foil surface upon friction of a steel roller lubricated with industrial oil containing 5% fullerene C60 was studied by optical and electron microscopy, X-ray diffraction (XRD) analysis, hardness measurements, and mass spectrometry. This protective film is probably a fullerene-polymer network formed by fullerene C60 and covalently bound fragments of hydrocarbon chains released in the course of mechanochemical degradation of the lubricating oil. The film exhibits elevated hardness and antiwear properties, and increases the load-carrying power of the tribotechnical unit. Chemical mechanisms of tribopolymerization were analyzed.

Thermal and tribological properties of fullerene-containing composite systems. Part 2. Formation of tribo-polymer films during boundary sliding friction in the presence of fullerene C60

The techniques of mass‐spectrometric thermal analysis, wide‐angle X‐ray diffraction, scanning and transmission electron microscopy, light microscopy, and hardness and tribological measurements were used for study of formation and properties of protective—anti‐wear and friction‐reducing—tribo‐polymer film forming on metal surfaces during sliding boundary friction, in the presence of fullerene C60 used as an additive to some mineral lubricating oils and greases. A possible mechanism of formation of tribo‐polymer film was proposed based on the idea of attachment of paraffin and naphthenic oligomers of the lubricants to C60 molecules, which in turn are polymerized and form a hard fullerene network with attached polyolefin chains. A fullerene network provides a high wear resistance while polyolefin chains provide some decrease in the friction coefficient and widening of the working intervals of friction joints.

Construction Of The Full Phase Diagram For The System Of Poly(γ-benzyl-l-glutamate)/dimethylformamide On The Basis Of The Complex Of Literature Data

The system poly-γ-benzyl-l-glutamate—dimethylformamide (PBG/DMF) is the most-studied of the rodlike polymer-solvent systems. However, up to now there is no satisfactory experimental phase diagram (PD) for this system in the entire range of concentrations. For all studied systems only fragments of the PD are known. Some regions of these fragments agree qualitatively with the theoretical PD for an ensemble of rodlike particles in an isotropic solvent. However, most parts of the PD do not agree with the theoretical ones. A critical analysis of the corresponding experimental data was carried out and on the basis of this analysis a new PD was constructed in the enti re range of concentration. The obtained PD differs essentially from the known theoretical diagram and is very close to the diagram predicted by Papkov taking into account the formation of crystallosolvates. The peculiarities of the phase transitions in the various regions of the PD are considered. It is shown that the so-named lyotropic liquid crystals (LC), on the basis of solved rodlike polymers, are thermotropic LCs diluted by the isotropic solvent. A specific role in the PD are played by the crystallosolvates (CS), which are identified with the phase defined by Luzzati as the “complex phase.” In particular, the phase region LC-CS exists instead of the LC-LC region in the theoretical PDs. Some new concepts of the crystallosolvate defects and on the “limiting” LC phase are discussed. Consideration of the liquidus lines CS/LC and CS/(isotropic liquid) permits us to propose some explanations of the PDs at low polymer concentrations. Most parts of the real PD represent the superposition of different phase equilibria and are complicated by the processes of gelation, crystallization and crystallosolvate formation that cannot be described by the modern theories. The fragments of the PDs in the literature for some rodlike polymers in solution agree well with the general PD for PBG/DMF. Special features of the phase transitions in the different areas of the PD are discussed. On the basis of the principles used in this work for construction of the PD, critical consideration of the PDs published in the literature have been carried out; our understanding of results obtained by other authors are presented. The perspectives of further investigations are considered.

Tribological characteristics of composites based on poly(tetrafluoroethylene) and fullerene carbon

The effect of fullerene carbon fillers on the antifriction characteristics and wear resistance of PTFE during its sliding friction on steel and water lubrication has been studied. The structures of the modified PTFE and the fullerence carbon filler are analyzed by small-angle and wide-angle X-ray diffraction. The hypothetical mechanism of reinforcing effect provided by the fullerene carbon filler during friction is proposed.

Effect of C60 fullerene additives on the structure and mechanical properties of thin organic glass films

We have studied the effect of small additives of C60 fullerene on the mechanical properties (strength, Young’s modulus, elongation at break) of thin organic glass films tested for uniaxial extension.

Supermolecular mobility and new concept of supermolecular organization in oriented semicrystalline polymers

The study of highly oriented films from a low-density polyethylene and other semicrystalline polymers by methods of small-angle and wide-angle x-ray scattering in a broad temperature range has been carried out. A new idea connecting the temperature of “a supermolecular mobility” T h (strictly speaking, about a range of temperatures) is introduced. After heating a polymer up to T h and higher temperatures, a sharp increase in the mobility of large supermolecular aggregates (such as crystallites and fibrils) can be observed by x-ray methods. Simultaneously, in the same temperature region, a wide spectrum of structure–mechanical property relationships changes their character. The nature of small-angle x-ray scattering reflections and the concept of supermolecular organization of oriented semicrystalline polymers are revised in light of these results.

Tribological properties of polytetrafluoroethylene modified with fullerene black in dry sliding friction

The effect of fullerene black introduced (after extraction of light fullerenes from the black with toluene) into polytetrafluoroethylene F-4 on its wear resistance and antifriction properties in sliding over steel at contact pressures in the range 0.2–2.0 MPa was studied.

Effect of fullerene black additives on boundary sliding friction of steel counterbodies lubricated with mineral oil

The effect of small additives of fullerene black (from 0.01 to 1 wt %) on the antifriction and anti-wear properties of a steel-steel pair lubricated with I-40A oil under boundary friction is studied. Based on the results of small-angle and wide-angle X-ray scattering it is suggested that more intensive dispersion of fullerene black in oil results in exposure of the crystalline grains of fullerene C60 and graphite.

Poly-p-phenyl sulfide as the material for oil-lubricated sliding bearings

Tribological analysis of two different poly-p-phenyl sulfides, with melt viscosity differing more than twofold, is performed. The tribological properties of the poly-p-phenyl sulfides are compared with those of the composites based on minced carbofibers with 0.5% of fullerene C60 by mass added into the matrix of the composites. In interpreting the tribological dependences it is especially noteworthy that the load-bearing capacity of the materials allows consideration of many of these dependences as phase diagrams.

Fullerene C60 Aggregates in Polymethyl Methacrylate Films

The structure of aggregates of fullerene C60 introduced into films of radical polymethyl methacrylate in the stage of solution preparation was studied by wide-angle X-ray diffraction.