Nanocomposite UHMWPE–CNT Polymer Coatings for Boundary Lubrication on Aluminium Substrates

Abstract

The boundary lubrication regime plays a very important role in determining the life span of any of the two mating parts under liquid-lubricated conditions. It is during the start\stop cycles when insufficient fluid is available to fully separate the surfaces in relative motion and thus unusual wear takes place; a case of boundary lubrication. The aim of this work is to study the feasibility of using polymer coatings as boundary lubricants. This study investigates the friction and wear properties of ultrahigh molecular weight polyethylene (UHMWPE) films coated on aluminium substrates under dry and base oil (without any additives)-lubricated conditions. In order to increase the load bearing capacity of the UHMWPE coatings, 0.1 wt% of single-walled carbon nanotubes are added. Experiments are carried out on a custom-built tribometer simulating a line contact between a polymercoated cylindrical Al surface (shaft) and a flat uncoated Al plate as the counterface. The experimental parameters such as the normal load and the sliding speed are selected to simulate the boundary and mixed lubrication regimes for comparison purposes. Specific wear rates of the polymer films and bare Al surface under lubricated conditions are also calculated. Stribeck curves have been generated to evaluate the effectiveness of the pristine UHMWPE and the nanocomposite coatings in the various regimes of lubrication, especially the boundary lubrication regime. It is observed that the selected polymer coatings are effective in protecting the metallic surfaces without causing any observable oil contamination with wear debris.

Tribological studies of epoxy and its composite coatings on steel in dry and lubricated sliding

“…Hence, in the current work, we have tested graphite and graphene filled epoxy as tribological coatings on steel for dry sliding as well as in the presence of base oil lubricant without the additives. Such coatings have the potential to be used as boundary layers for the protection of steel and other metallic substrates 16 .…”

Crystallization and stress relaxation behaviors of UHMWPE/CNT fibers

“…Several studies have shown that the addition of CNTs resulted in significant improvements in the mechanical properties such as the tensile modulus and strength of the polymer matrices. In addition, an increase in the wear resistance of bulk UHMWPE with the CNTs addition has also been observed . However, very few studies have been reported on stress relaxation behaviors of the UHMWPE/CNT composites.…”

Carbon Nanotube‐Based Reinforced Polymers for Medical Applications: Improving Impact Strength of Polymer‐Polymer Composites

“…Therefore, two approaches are commonly used to improve the UHMWPE and HDPE performance, which is crosslinking and reinforcement [21,29]. The reinforcement of UHMWPE is often realized by addition of particles or nanofillers, such as titanium dioxide (TiO 2 ), aluminum oxide (Al 2 O 3 ), graphene, silica nanoparticle, and carbon nanotubes (CNTs) [27,[30][31][32][33][34][35].…”