Tribological Performance of Epoxy/Polyurethane Composites at a Wide Temperature Range

The work aims to investigate the tribological performance of epoxy/polyurethane (EP/PU) interpenetrating network (IPN) composites under various working conditions and study the effects of graphene oxide (GO) on the friction and wear of epoxy/polyurethane IPN composites at different temperature and sliding speed. Firstly, polyurethane prepolymer with terminal isocyanates and terminal hydroxyl groups was prepared by a two-step method. Then, polyurethane pre-polymer was thoroughly mixed with EP at a weight ratio of 3:1 for 1 h in a three-mouth flask. Meanwhile, an appropriate amount of MOCA was added into a flask and melt, then an appropriate amount of GO (1.0wt.%) was added into the above flask and stirred evenly. Next, the mixture of MOCA and GO was added into the reaction system of EP and was mixed for 1 h. After reaction, the resulting mixture was cast onto the substrate and placed on the heating platform at 80 ℃ for 1 h and finally put in muffle furnace at 100 ℃, 160 ℃ and 180 ℃ for 60 min, 60 min and 100 min, respectively. The preparation process of EP, EP/GO, and EP/PU was similar to that of EP/PU/GO. The composite structure was confirmed by FT-IR spectra and the thermodynamic properties of the composite materials were studied through thermogravimetric analysis. Moreover, the effects of graphene oxide (GO) on the friction and wear of epoxy/polyurethane IPN composites at -100 ℃, -50 ℃, 50 ℃, and 100 ℃ were studied by a high and low temperature friction tester. The worn surfaces of the composites were observed with optical microscope and Scanning Electron Microscope (SEM), and the nanostructure of the tribological film was detected through SEM. In addition, X-ray Photoelectron Spectroscopy (XPS) was used to analyze the chemical state and formation mechanism of the tribological film. The results showed that the tribological performance of epoxy/polyurethane was significantly improved by adding GO. The thermodynamic results showed that the initial decomposition temperature decreased due to the addition of polyurethane and increased due to the addition of GO. The tensile strength of EP was the highest, about 90 MPa. At room temperature, the friction coefficient and wear rate of all the samples at 200 r/min were almost better than those at 400 r/min and 500 r/min, and the friction coefficient decreased after the introduction of GO compared with the composite coating with the same substrate material. The friction coefficient of EP/PU/GO at 200 r/min was the lowest 0.03. At -100 ℃, the friction coefficient was relatively high, especially for EP and the friction coefficient was the highest (0.7). With regard to EP/PU/GO, the friction coefficient was reduced to about 0.23. Moreover, compared with EP, EP/GO and EP/PU, EP/PU/GO displayed excellent lubrication and the coefficient of friction was less than 0.2 at -50 ℃, 50 ℃ and 100 ℃, respectively. SEM and XPS results showed that the tribo-oxidization and chelation reaction promoted the growth of the transfer film, which could avoid the direct contact of the sliding interfaces and achieve the lubrication. The addition of GO can effectively improve the mechanical properties of the material and the tribological performance of epoxy/polyurethane. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.