Lubricating Effect Of Seawater Research Articles

Influence of graphene oxide as filler on tribological behaviors of polyimide/graphene oxide nanocomposites under seawater lubrication

Polymer-based composites reinforced by lubricated fillers have aroused wide concern in the field of tribology. In this manuscript, the effect of graphene oxide (GO) as lubricated filler on the tribological behaviors of polyimide (PI)/graphene oxide (GO) nanocomposites prepared by hot press molding method was investigated under seawater to provide a practical guidance for the use of the polymer-based composites in ocean environment. It was found that the incorporation of GO could greatly improve the wear resistance of pure PI under seawater lubrication, especially when the content of GO was about 0.5 wt%. This was due to the lubricated effect of GO. In addition, PI/GO nanocomposites exhibited better friction and wear properties under seawater-lubricated condition than that under dry friction condition because of excellent lubricating effect of seawater. Optical photographs of the worn surface morphology had revealed that the main wear mechanism of the PI/GO nanocomposites was slight abrasive wear.

Effect of MWCNTs-COOH Reinforcement on Tribological Behaviors of PI/MWCNTs-COOH Nanocomposites Under Seawater Lubrication

The carboxyl-functionalized multiwalled carbon nanotube (MWCNT-COOH) was achieved by grafting carboxyl (COOH) groups onto surfaces of MWCNTs. Then polyimide (PI)-based nanocomposites reinforced with MWCNTs-COOH and MWCNTs were prepared by in situ polymerization and the tribological behaviors of PI/MWCNTs-COOH and PI/MWCNT nanocomposites were studied under dry friction and seawater lubrication. The results showed that the incorporation of MWCNTs-COOH and MWCNTs could greatly improve the wear resistance of PI because of the lubricating effect of MWCNTs-COOH and MWCNTs. In additon, the PI/MWCNTs-COOH exhibited better tribological performance than the PI/MWCNTs under dry friction due to functionalization of MWCNTs. In addition, PI/MWCNTs-COOH nanocomposites presented better tribological properties under seawater lubrication than other conditions because of the excellent lubricating effect of seawater, especially when the content of MWCNTs-COOH was 0.7 wt%. Furthermore, the effects of applied load and sliding speed on the tribological behaviors of PI/MWCNTs-COOH nanocomposites were studied under seawater lubrication. It was found that 0.7 wt% PI/MWCNTs-COOH nanocomposites had the best friction reduction and antiwear properties when the applied load and sliding speed were 3 N and 0.26 m/s, respectively, under seawater lubrication.

Microstructure of PTFE-Based Polymer Blends and Their Tribological Behaviors Under Aqueous Environment

Four polytetrafluoroethylene-based polymer blends (PTFE blends) with polyimide (PI), polyether ether ketone (PEEK), poly(phenyl p-hydroxybenzoate) (PHBA), and perfluoroethylene propylene copolymer (FEP) were prepared by compression molding and follow-up sintering. Their microstructure was observed by scanning electron microscope. And the tribological behaviors of PTFE blends sliding against 316 steel under pure water and sea water lubrication were comparatively evaluated using block-on-ring tribology test rig. The worn surface of counterpart was examined by X-ray photoelectron spectroscopy. The results showed that by blending with the four polymers, PTFE exhibited the transformed microstructure and improved wear resistance. Compared with FEP, rigid polymers PI, PHBA, and PEEK can enhance the wear resistance of PTFE greatly because they can effectively improve the load-carrying capacity of PTFE matrix and can more efficiently prevent the crystalline bands of PTFE from being pulled out. However, because of the weak inhibition on the pulling out of PTFE crystalline bands, FEP cannot enhance the wear resistance of PTFE as significantly as other polymers. In addition, the friction coefficients and wear rates of PTFE and its blends were lower under the lubrication of sea water than under the lubrication of pure water, which was ascribed to more excellent lubricating effect of sea water originating from the deposition of CaCO3 and Mg(OH)2 onto the sliding surfaces.

Tribological behaviors of some polymeric materials in sea water

Ocean tribology, a new research field of tribology, is being established and developing. The investigation on the tribology in sea water has important significance to ocean exploitation. In this paper, the tribological behaviors of UHMWPE, PTFE as well as Ekonol/PTFE, graphite/PTFE and CF/PTFE sliding against GCr15 steel and Ni-Cr-WC alloy in sea water were investigated, and compared with those in pure water. Results show that the main factors that affect the tribological behaviors of five polymeric materials in sea water are the corrosive effect and lubricating effect of sea water. When polymeric materials sliding against GCr15 in sea water, owing to serious corrosion of counterface by sea water, the surface roughness of the counterface increases largely. As a result, the lubricating effect of medium decreases sharply and the plowing effect of counterface increases greatly. So the friction coefficients and wear rates of five materials sliding against GCr15 in sea water are much larger than those under other conditions. Such wear model, depending on the corrosion of counterface by medium, can be called indirect corrosive wear. Under other three conditions, owing to the more superior lubricating effect of sea water than pure water and the better wettability of Ni-Cr-WC than GCr15, the friction coefficients and wear rates of five materials increase in the following order: sliding against Ni-Cr-WC in sea water < sliding against Ni-Cr-WC in pure water < sliding against GCr15 in pure water. Moreover, compared with other materials, CF/PTFE is the one with more superior plowing and wear resistance in pure and sea water, which is a potential frictional material well suitable for pure and sea water lubrication.