Perspective for the use of industrial waste in lubricating compositions to reduce wear in friction pairs

The article presents an analysis of the mechanisms of lubricating action used to reduce the wear of rails and wheels. A review of lubricant compositions that increase the service life of the wheel-rail pair showed that graphite is the main filler used to create rail lubricants. Since the production of synthetic graphite requires high energy costs, this material is relatively expensive. Replacing graphite with cheaper analogs will help reduce the cost of operating rails without losing lubricating properties in friction pairs. Today, there are many lubricant compositions. Many of them require experimental research since they are based only on theoretical knowledge in the field of tribology. In addition, the adhesion properties of a wheel to a rail depend not only on the action of the lubricant but also on weather and climatic conditions. When choosing a rational lubricant, it is worth focusing on a set of factors, and not only on the properties of an individual filler. The data obtained in theoretical analysis cannot always be verified experimentally. The reasons may be economic inexpediency, the complexity of experimental research, or lack of time. The analysis carried out in the course of this work showed that the study of the effect of lubricant components could be optimized using mathematical and digital modeling. The application of these methods will help to select a rational area for research, simulate the behavior of lubricants containing production wastes, and make the mathematical forecast of the operation of friction pairs more accurate.

Comparative study of flexural and physical properties of graphite-filled immiscible polypropylene/epoxy and high-density polyethylene/epoxy blends

Polypropylene/epoxy/synthetic graphite (PP/EP/SG) and high-density polyethylene (HDPE/EP/SG) composites were prepared by melt mixing followed by compression molding. The immiscibility of the polyolefins with epoxy was confirmed by thermogravimetric analysis. Scanning electron microscopy (SEM) studies showed that HDPE/EP blend exhibits inferior interfacial adhesion between the component polymers compared to PP/EP blend. Also, the effect of SG content on flexural properties, density, moldability, water absorption, and porosity of the PP/EP/SG and HDPE/EP/SG composites was investigated. For both PP/EP/SG and HDPE/EP/SG composites, flexural modulus, density, and porosity increased with increase in SG content. For PP/EP/SG composites, the water absorption decreased from 0.154% at 30 wt% SG to 0.072% at 70 wt% SG. Further increase in SG content to 80 wt% caused an increase in water absorption. On the other hand, water absorption for HDPE/EP/SG increased with SG content all through. At the same filler loadings, PP/EP/SG composites showed lower density and porosity and performed better in terms of flexural modulus and water absorption compared to HDPE/EP/SG composites.

Improving thermal conductivity of polybutylene terephthalate composites with hybrid synthetic graphite and carbon fiber

Polybutylene terephthalate (PBT) is a semi-crystalline engineering thermoplastic polyester. PBT offers rapid molding cycles, high heat resistant, crystallinity, fatigue resistance, strength and rigidity, excellent electrical properties, creep resistance, reproducible mold shrinkage and chemical resistance. In this study, PBT was loaded with synthetic graphite and carbon fiber at different weight fractions (10–40 wt.%). PBT-based composites were fabricated by the melt mixing process by using a co-rotating twin screw extruder then thermal, mechanical and morphological properties of filled PBT composites was investigated. Weight fraction of carbon fiber (up to 30 wt.%) increases the tensile strength and flexural strength of PBT, but synthetic graphite loading decreases the tensile strength and flexural strength of PBT. The highest in-plane and through-plane thermal conductivity values were obtained as 9.24 for 40 wt.% synthetic graphite filled composite and 3.41 W/mK for 40 wt.% carbon fiber reinforced composite, respectively. Carbon fiber was found to be more effective in increasing the through-plane thermal conductivities than synthetic graphite.

Properties of synthetic graphite from boric acid-added pitch: performance as anode in lithium-ion batteries

Synthetic graphite is produced by a heat treatment process using a carbon precursor (pitch, coke), but it is difficult to produce synthetic graphite of high quality due to the high-temperature process (minimum 3000 °C). Elements used as additive to lower temperature the graphitic process include boron, phosphorus, and nitrogen. Boron is known as a graphitization additive, because it accelerates the homogeneous continuous graphitization process of the entire carbon without any formation of specific carbon components such as graphite. In this study, various amounts of boron and PFO (pyrolysis fuel oil, carbon precursor) were used in an attempt to reveal the boron additive effect. Pitch was produced using a boric acid and pyrolysis fuel oil (PFO), and high-temperature carbonization was carried out at 2600 °C. As a result, synthetic graphite exhibiting high crystallinity at a relatively low temperature was produced. The electrochemical performance of several boron-doped and non-doped carbon materials with different structures as anodes in lithium-ion batteries was investigated by a structure analysis.

Tribological, Mechanical and Thermal Properties of Fluorinated Ethylene Propylene Filled with Al-Cu-Cr Quasicrystals, Polytetrafluoroethylene, Synthetic Graphite and Carbon Black

Antifriction hybrid fluorinated ethylene propylene-based composites filled with quasicrystalline Al73Cu11Cr16 powder, polytetrafluoroethylene, synthetic graphite and carbon black were elaborated and investigated. Composite samples were formed by high-energy ball milling of initial powders mixture with subsequent consolidation by injection molding. Thermal, mechanical, and tribological properties of the obtained composites were studied. It was found that composite containing 5 wt.% of Al73Cu11Cr16 quasicrystals and 2 wt.% of nanosized polytetrafluoroethylene has 50 times better wear resistance and a 1.5 times lower coefficient of dry friction comparing with unfilled fluorinated ethylene propylene. Addition of 15 wt.% of synthetic graphite to the above mentioned composition allows to achieve an increase in thermal conductivity in 2.5 times comparing with unfilled fluorinated ethylene propylene, at that this composite kept excellent tribological properties.