RESUMO
In this study, the friction and wear characteristics of polydimethylsiloxane (PDMS) were evaluated when using lubricants created by adding surfactants at various ratios to deionized (DI) water. When pure DI water is used as a lubricant, the repulsion of water from the hydrophobic PDMS surface is large and the interfacial affinity is low; thus, the lubrication properties cannot be significantly improved. However, when a lubricant with a surfactant is added to DI water, the interfacial affinity with the PDMS surface increases to form a lubricating film, and the friction coefficient is greatly reduced. In this study, under dry and pure DI water conditions, severe wear tracks were formed on the PDMS surface after 10,000 cycles of reciprocating sliding motion under a vertical load of 100 mN, whereas in the case of the surfactant-based and water-based lubricant, no severe wear tracks occurred. The friction and wear characteristics of the PDMS were evaluated by increasing the normal loads and sliding cycles with a water-based lubricant containing 1 wt % surfactant. Under normal loads of 300 mN and 500 mN, only minor scratches occurred on the PDMS surface up to 10,000 and 100,000 cycles, respectively, but after 300,000 cycles, very severe pit wear tracks occurred.
RESUMO
In this study, the friction and wear characteristics of graphene coatings were evaluated using lubricants with various ratios of graphene ink to deionized (DI) water. When dry graphene ink and pure DI water were used as lubricants, the graphene coating initially peeled off, and the friction coefficient rapidly increased to a large value. However, when a lubricant with graphene ink added to DI water was used, a lubricating film was formed on the graphene coating and the friction coefficient was reduced significantly. Under dry and pure DI water conditions, severe wear morphologies were formed on the graphene coating surface, whereas in the case of the lubricant with graphene inks added to DI water, insignificant wear morphologies were formed. When the mixing ratio between DI water and graphene ink was 100:10 and 100:5, the friction coefficient and wear rate were the lowest, respectively. As a result of a long-term experiment in which the sliding cycle was performed for up to 100,000 cycles under the same experimental conditions, the lubricant with a 100:10 mixing ratio showed excellent lubrication properties, confirming that the friction coefficient and wear rate were significantly reduced compared to that of the dry or pure DI water lubrication conditions.
