Effect of Argon Plasma Treatment on Tribological Properties of UHMWPE/MWCNT Nanocomposites

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) is widely used in artificial joints in the replacement of knee, hip and shoulder that has been impaired as a result of arthritis or other degenerative joint diseases. The UHMWPE made plastic cup is placed in the joint socket in contact with a metal or ceramic ball affixed to a metal stem. Effective reinforcement of multi-walled carbon nanotubes (MWCNTs) in UHMWPE results in improved mechanical and tribological properties. The hydrophobic nature of the nanocomposites surface results in lesser contact with biological fluids during the physiological interaction. In this project, we investigate the UHMWPE/MWCNTs nanocomposites reinforced with MWCNTs at different concentrations. The samples were treated with cold argon plasma at different exposure times. The water contact angles for 60 min plasma-treated nanocomposites with 0.0, 0.5, 1.0, 1.5, and 2.0 wt % MWCNTs were found to be 55.65˝, 52.51˝, 48.01˝, 43.72˝, and 37.18˝respectively. Increasing the treatment time of nanocomposites has shown transformation from a hydrophobic to a hydrophilic nature due to carboxyl groups being bonded on the surface for treated nanocomposites. Wear analysis was performed under dry, and also under biological lubrication, conditions of all treated samples. The wear factor of untreated pure UHMWPE sample was reduced by 68% and 80%, under dry and lubricated conditions, respectively, as compared to 2 wt % 60 min-treated sample. The kinetic friction co-efficient was also noted under both conditions. The hardness of nanocomposites increased with both MWCNTs loading and plasma treatment time. Similarly, the surface roughness of the nanocomposites was reduced.

Effect of argon plasma treatment on hydrophilic stability of nanofiber webs

“…During the plasma treatment, highly reactive species were produced and generated a large variety of functional groups on the surface of the samples . Kumar et al . observed a significant reduction in contact angle with plasma treatment of 5 min or longer.…”

“…Using plasma technology, the polymer surface can be modified either by introducing functional groups or by surface grafting. Organic or inorganic films with the demanded functionalities can also be deposited on the surface by coating methods . Some other applications of plasma modification include gas separation, oil–water separation, and self‐cleaning and adhesion of surfaces, to name a few …”

Tribological Behaviour of Polymers in Terms of Plasma Treatment: A Brief Review

“…UHMW-PE treated by a cold argon plasma using dielectric barrier discharge (DBD) supports such a finding since (under dry conditions) an increase in the friction coefficient with treatment time was observed whereas the wear volume reduced over the treatment time due to modifications of its surface. Under normal saline (N-saline) lubrication conditions, wear volume and friction were reduced over the treatment time which is indicative of an increase in surface wettability and, therefore, enhanced surface lubrication capability [70]. Sagbas [71] reported an increase in friction and improvement in the wear properties of conventional UHMW-PE after plasma treatment, whereas the friction coefficient was unaffected in terms of vitamin-E-blended UHMW-PE under the same test conditions.…”

Friction Behavior of Engineering Polymers Treated by Atmospheric DBD Plasma

“…The DCSBD was designed to be suitable for flat surfaces treatment in particular. The DCSBD electrode system was powered by AC high voltage source which has a frequency (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) kHz and approximately 20 kV peak-to-peak voltage. In the present study, the discharge power is 320 W and it was operated in the air in order obtain a quasi-homogeneous diffuse plasma surface.…”

“…This increase indicated to the presence of polar functionalities on the surface. The surface roughness is an important parameter, which influences the tribological behavior of the polymer [17]. Surface topography of pristine and plasma treated samples were monitored by non-contact profilometry, illustrated by 3D surface scans for PA6 E and PETP in Fig.…”