Surface treatments of nitrile butadiene rubber to enhance wear resistance and mechanical properties

Objectives. The aim of this work is to investigate rapid surface treatment methods of nitrile butadiene rubber (NBR) using an elastomer composition based on fluoropolymer FKM-32 and fluoroplastic F32L. The article presents new methods for enhancing the mechanical and wear properties of NBR by applying surface coatings.

Methods. Abrasion tests were conducted using an MI-2 tribometer; determination of the tensile strength properties of the samples was performed using a DVT GP UG 5 universal testing machine (Devotrans, Turkey). Hardness was ascertained using a Shore A type durometer. Samples were cut out on a pneumatic punching press GT-7016-AR (GOTECH Testing Machines Inc., Istanbul, Turkey). Microstructure and elemental composition studies were carried out using a Vega 3 scanning electron microscope (TESCAN, Brno, Czech Republic) equipped with an X-Act (Oxford Instruments, High Wycombe, United Kingdom) energy-dispersive analysis attachment.

Results. The immersion of NBR in a 10% solution of poly(vinylidene fluoride-co-chlorotrifluoroethylene) (fluoroplast F32L) in 1,1,2-trifluoro-1,2,2-trichloroethane was found to result in the formation of a uniform fluoropolymer-based coating on the rubber surface. This coating results in a decrease in the abrasion value from 0.046 to 0.005 m³/TJ, corresponding to an increase in abrasion resistance. Furthermore, for rubbers coated by immersion in the fluoroplastic solution, the modulus at 100% and 300% strain increases by 86% and 44%, respectively, while the tensile strength increases by 20%, and the hardness increases by 9 units compared to the as-obtained NBR.

Conclusions. Regardless of pre-soaking in methyl ethyl ketone, the wear resistance of the synthetic rubber is not increased by surface treatment with elastomeric composition based on fluororubber FKM-32 grade followed by thermostating. However, surface-modification of NBR using the M3 method demonstrates better tribological performance and mechanical performance than the untreated sample. A complex of enhanced properties of surface-modified NBR-M3 can be effected by the presence of halogen atoms on the surface layer of the rubber sample.

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