Effects of silane coupling agents on tribological properties of bentonite/nitrile butadiene rubber composites

In this work, effects of silane coupling agents on the tribological properties of bentonite/nitrile butadiene rubber (NBR) composites were investigated. The composites were fabricated with a facile method. Three silane coupling agents, (3-mercaptopropyl)trimethoxysilane (MPTMS), bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT) and [3-(2-aminoethylamino)propyl]triethoxysilane (AEAPTMS) were employed in our research. The short sulfur bonds formed between MPTMS and macromolecules in the matrices limited the extension of the contact interface between rubber matrices and glass plate, which contributed to the reduction in friction coefficient. With TESPT and AEAPTMS, the adhesion force of the composites was remarkably reinforced, further leading to the increase in friction coefficient. In the wear test, bentonite/silane/NBR composites showed better wear resistance compared to the specimens fabricated without silanes. By investigation on the morphological features of the worn surfaces, different wear mechanisms for composites with/without silane coupling agents were illustrated in detail. Generally, the effects of silanes to adhesion force, hysteresis loss ratio and hardness all contributed to the friction coefficients of the composites. In wear test, the effects of the silanes on hysteresis force were prominent. Incorporated with MPTMS, the composite showed poor wear resistance due to its high hysteresis loss ratio.