The influence of filler filling structure and filler shape on the composite properties is reviewed. The compound processes of composites and the dispersion mechanism of fillers in polymer, the surface treatment of fillers, and the interfacial structure of composite are introduced. The key points of composites for sliding materials are discussed.

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Polytetrafluoroethylene (PTFE) is widely used as a tribomaterial because it shows excellently low friction coefficient when it slides against metal surface. The wear rate of PTFE, however, is unacceptably high in comparison with other plastics. In the early days of research into improving the wear resistance of PTFE, many results were reported on the effects of adding macro-sized fillers. Recently, there has been an increase in research using nanomaterials as PTFE fillers. It has also become clear that the addition of these fillers enhances the tribochemical reaction between PTFE and the sliding counter surface. However, there is still little knowledge about the effects that fluorination of the counter surface has on the counter material. Incidentally, there is a movement in Europe to regulate all PFAS including PTFE. Although this is an ongoing issue, the current situation will be summarized and reported here.

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Polyimide exhibit excellent heat resistance, mechanical strength, electrical properties, environmental resistance, and flame retardancy among super engineering plastics. They are utilized in a wide range of fields and various product forms. This article begins with the history of polyimide and introduces the characteristics attributed to their chemical structure, along with examples of tribological applications that leverage these properties. PMDA-ODA type aromatic polyimide as representative of linear non-thermoplastic polyimides is mainly mentioned in this article. By combining excellent tribological properties with other unique characteristics of polyimide, they are expected to contribute to miniaturization, high performance, and longer lifespan of components in various fields in the future as well.

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We introduce the tribological properties of tribomaterials of biomass polyamide (PA) in this paper. Biomass polymers have the potential to reduce environmental impacts related to petroleum-based plastics, including oil depletion, waste problems, and marine plastic litter. In particular, biomass PA1010 is a kind of engineering plastic and semi-crystalline polymer and has unique performances such as high heat resistance, high mechanical strength, flexibility and low water absorption among biopolymers. To effectively use biomass PA1010 in the industry for polymeric tribomaterials, we investigated the enhancement of the tribological properties of biomass PA1010 using material design and polymer processing techniques. Specifically, this paper reported the influence of five types: ( i ) gamma-irradiation dose and the addition of the cross-linking agent (TAIC), (ii) content of TAIC, (iii) surface treatment of fiber using silane coupling agent, (iv) the addition of biomass thermoplastic elastomer and (v) screw configurations in a twin-screw extruder on the tribological properties of biomass PA1010.

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Hydrogen is expected to be a clean and renewable energy carrier which is essential for realizing green transformation (GX) and achieving carbon neutrality in 2050. Fuel cells, a typical hydrogen utilization system, require extremely high purity hydrogen and the use of volatile lubrication oils and greases is strictly forbidden for machine components of hydrogen supply infrastructures. As a result, resin composites with superior self-lubrication ability are preferably used as bearing materials in hydrogen utilization systems. However, there are strong demands for improving mechanical strength and wear resistance of resin composites used in current hydrogen infrastructures. This paper focuses on a hydrogen refueling station (HRS) as a conspicuous example of currently developing hydrogen infrastructure and introduces resin composite bearing materials used in it and related tribological studies.

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In recent years, environmental pollution caused by the discharge of lubricating oil into rivers and oceans has become an issue, and many applications, such as hydroelectric power generation equipment and ships, have been converting to oil-free lubrication systems. In addition, the frequent occurrence of typhoons and guerrilla torrential rains has also increased the demand for underwater robots and submersible pumps, which in turn has increased the demand for water-lubricated bearings. However, the viscosity of water is much lower than that of lubricating oil, limiting water film formation due to hydrodynamic effects and causing water-lubricated systems to operate in the mixed or boundary lubrication regime. Therefore, the development of tribo-materials that exhibit low friction and wear in water and under a wide range of loads and sliding speeds is required to realize water-lubricated systems. This article describes research of tribological properties of resin materials and resin composites under water lubrication and introduces friction and wear properties of resin-based composites filled with hard porous carbon particles made from rice bran under water lubrication.

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[in Japanese]

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