Xiaohua Lu

Comparative Study of Tribological Properties of Different Fibers Reinforced PTFE/PEEK Composites at Elevated Temperatures

The friction and wear properties of PTFE/PEEK composites filled with potassium titanate whisker (PTW) or short carbon fiber (CF) at elevated temperatures (160, 180, 200, 220, and 240°C), different loads (100 and 200 N), and various sliding velocities (0.7 and 1.4 m/s) were investigated in this article. The results show that the friction coefficient of PTW/PTFE/PEEK composites is more stable and 30% lower than that of CF/PTFE/PEEK composites at various sliding conditions. Moreover, it is found that the wear rate of PTW-filled PTFE/PEEK composites is only 10 to 40% that of CF/PTFE/PEEK composites. The wear rate of PTW/PTFE/PEEK composites is only 20% of CF/PTFE/PEEK composites at 200 N, 1.4 m/s, and 240°C. Scanning electron microscopy (SEM) study reveals that PTW can reduce the adhesive wear of PTFE/PEEK composites.

Friction and Wear Behavior of CF/PTFE Composites Lubricated by Choline Chloride Ionic Liquids

The use of ionic liquids (ILs) as lubricants has received increasing attention in recent years. The use of ILs, however, is limited by the corrosion problem and their potential toxic property. Here we present the results of our initial study on the tribological properties of carbon fiber (CF)-filled polytetrafluoroethylene (PTFE) composites, which have an excellent chemical resistance property, lubricated by choline chloride ILs. The difference between choline chloride ILs and water and hydraulic oil as lubricants was studied at the same time, as was the effect of the anion on the lubricating property of choline chloride ILs. The worn surface and transfer film of CF/PTFE composites were studied by scanning electron microscopy. Our results indicate that the lubricating property of choline chloride ILs is much better than that of water and hydraulic oil. The friction coefficient and wear rate of CF/PTFE composites lubricated with ILs were approximately 60 and 50xa0% lower than those under the dry friction condition. Among the three kinds of ILs tested, the best tribological properties of the CF/PTFE composites were found for those sliding in the mixture of 1,2-propanediol and choline chloride. The worn surface and transfer film of CF/PTFE composites were also much smoother than those under the dry friction, water lubrication, and hydraulic oil lubrication conditions.

Right Way of Using Graphene Oxide Additives for Water-Lubricated PEEK: Adding in Polymer or Water?

Water-lubricated polymer is attracting more and more interest from the industry. Adding nanoparticles is considered to be an effective way to improve the tribological performance. In this work, water-lubricated Polyetheretherketone (PEEK)-steel contacts were employed as the objects of study. A careful comparative study was made by investigating the effect of adding graphene oxide (GO) into water or into PEEK. Results show that adding GO into water can significantly reduce the wear and friction coefficient of pure PEEK, which is much more effective than adding GO into PEEK. Under the lubrication of GO aqueous dispersion, the wear of PEEK remains very low even under a harsh condition where the pressure reaches 50xa0MPa and the linear sliding speed is 0.7xa0m/s. Neat PEEK and GO/PEEK composites in pure water exhibit serious wear under this harsh condition. The excellent lubricating properties of GO aqueous dispersion are attributed to GO nanosheets entering into solid contacts, which can not only form a protective layer on steel counterpart repairing the worn surface, but also strongly adhere to the PEEK matrix resulting in an in situ-formed GO coating and prevent the scratch by steel counterpart.