| Feb 01, 2023 |
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(Nanowerk News) Mineral oil lubricants protect engine parts from wear, and this effect is enhanced by adding polymer nanoparticles to the lubricating oil. A UK team has now discovered that epoxy functionalization of these nanoparticles further promotes friction reduction on metal surfaces. As the team reports in the journal Angewandte Chemie (“Enhanced Adsorption of Epoxy-Functional Nanoparticles onto Stainless Steel Significantly Reduces Friction in Tribological Studies”), nanoparticles containing epoxy groups adhere strongly to stainless steel surfaces, which leads to a significant reduction in friction.
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| Enhanced Adsorption of Epoxy-Functional Nanoparticles onto Stainless Steel Significantly Reduces Friction in Tribological Studies. (© Wiley)
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Automotive engines comprising well lubricated parts consume less fuel, produce lower emissions, and suffer less long-term wear. Mineral oil is widely used as a lubricant, and nanoparticles can be directly prepared within this solvent using a technique known as polymerization-induced self-assembly. Coating the surface of the metal components with nanoparticles of a few dozen millionths of a millimeter in size protects them from direct contact.
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Csilla György and Steve Armes at the University of Sheffield (UK) designed “hairy” nanoparticles comprising oil-soluble poly(lauryl methacrylate) chains and an oil-insoluble nanoparticulate core. These nanoparticles were made to stick strongly to metal surfaces by introducing epoxy groups into the “hairs” by copolymerizing lauryl methacrylate with glycidyl methacrylate, an epoxy-functional monomer.
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The team found that the epoxy-bearing nanoparticles reacted with hydroxy groups located at the surface of stainless steel. This reaction led to strong adhesion of the nanoparticles, a phenomenon known as chemical adsorption. Whether chemical adsorption occurred or not depended on the precise location of the epoxy groups. “To our surprise, introducing a far larger number of epoxy groups into the nanoparticle cores had no beneficial effect,” explains Armes.
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The adsorbed nanoparticles reduced friction significantly, as the Sheffield team discovered when conducting tribological studies in collaboration with scientists at Lubrizol, an engine oil additives company based in the UK.
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“Remarkably, the adsorbed nanoparticles remained intact on the stainless steel surface after such experiments, which were conducted at the typical operating temperature of an internal combustion engine,” Armes adds.
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Such epoxy-functionalized nanoparticles could therefore mean a further leap in performance for lubricant additives for next-generation engine oil formulations.
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