Research Progress on Antifriction and Anti-Wear Modification of Rubber

Rubber is a versatile material that is widely used in various industries, such as national defense, aerospace, automotive, electrical and electronic, petrochemical, and more. It is known for its excellent physical and chemical properties, as well as its unique mechanical properties, which make it ideal for shock absorption, cushioning, sealing, and other applications. However, despite its many advantages, rubber can suffer from issues related to friction and wear, including a large friction coefficient, adhesion, friction heat generation, mechanical wear, and abrasive wear. These problems can lead to a deterioration of the material's performance or even failure in certain applications, such as piston rod, valve shaft (rod) seals, tires, and water-lubricated bearings. This paper reviewed the theory of rubber tribology and wear, then described the progress that had been made in developing antifriction and anti-wear methods. Three main approaches had been explored including rubber substrate modification, rubber surface treatment and surface texturization. First of all, rubber substrate modification involved adding different inorganic fillers and organic resins to improve the friction and wear properties of the rubber matrix. Inorganic fillers could be anti-wear or self-lubricating which were used to either reinforce the rubber material or rely on their own lubrication effect to decrease the friction coefficient. Adding organic resin to the rubber material could create dual properties, achieving both anti-wear and friction reduction effects. Secondly, rubber surface treatment methods included surface modification and surface coatings. Surface modification used the reactivity of the special functional group of the rubber matrix to chemically modify the rubber surface, increasing its surface denseness, hardness, finish and anti-corrosion properties. This approach achieved the purpose of friction and wear reduction by changing the structural form and group properties of the rubber surface. Surface coatings, on the other hand, involved depositing or coating the rubber surface with a lubricant coating to form a transfer film, which significantly reduced friction and wear by improving surface flatness and hardness. Lastly, textured surfaces with a certain size and distribution of pattern arrays had been found to achieve excellent tribological performance for rubber surfaces. There were many types of textured surface, mainly convex bodies, pits, grooves and various types of mixed morphologies, with pits and grooves being the main types studied. The groove structure had the effect of forming, replenishing and stabilizing the lubricant oil film as well as storing the abrasive chips to achieve the goal of anti-friction. In summary, the progress made in these three areas offered promising avenues for the development of better antifriction and anti-wear methods for rubber materials in the future. In the end, the review provided an outlook and recommendation on the development prospects of rubber tribology.