Effect of Platelet Thickness on Wear of Graphene–Polytetrafluoroethylene (PTFE) Composites

Abstract

Under conditions of dry sliding against polished stainless steel, the steady-state wear rates of composites of polytetrafluoroethylene (PTFE) filled with graphene platelets with typical platelet thickness varying between 1.25 and 60 nm were measured. The fraction of the graphene platelets was varied between 0.02 and 30 wt%, also including 0 % unfilled PTFE. With 4 % loading of the 1.25 and 1.6 nm thick graphene platelets, the measured steady-state wear rates approached *4 9 10 -7 mm 3 /Nm levels which are roughly three orders of magnitude lower than that measured for unfilled PTFE, decreasing further to 10 -7 mm 3 /Nm at 10 % loading. In addition, among all the tested graphene platelets, the thinnest graphene platelets already imparted considerable wear resistance even at a low 0.32 % loading. The thicker graphene platelets also started providing some slight resistance to sliding wear but not until a greater filler loading of 1.1 %. For a given graphene platelet, there appears to be a lowest achievable steady-state wear rate, while the filler loading is gradually increased. For the 8 nm thick graphene platelets, this minimum was found to be about 3 9 10 -7 mm 3 /Nm at a filler loading of about 20 %. When the wear rates are plotted as a function of the filler loading on log-log axes, for each of the graphene platelets, the wear rates are found to decrease linearly beyond a threshold filler loading up to at least 10 % filler loading. Wear rates corresponding to each type of graphene platelet fall on its own line on such a plot. However, when the wear rates are instead plotted as a function of the filler surface area available per unit mass of the composite, the data (with the exception of the thickest 60 nm platelets) collapse around a master line with slope of about -1.73.

Tribological and mechanical properties of graphene nanoplatelet/PEEK composites

“…3 Several works in the literature have assessed the influence of graphene fillers on the tribological and mechanical properties of different polymers, such as polyacrylonitrile [15], poly(vinyl chloride) [16], polyimide [17], polytetrafluorethylene (PTFE) [18] and ultrahigh molecular weight polyethylene [19]. However, only a few works have appeared about graphene/PEEK composites [20][21][22][23].…”

“Ultralow” sliding wear polytetrafluoro ethylene nanocomposites with functionalized graphene

“…In fact, incorporation of alumina [6], serpentine [7] nanoparticles enhanced the wear resistance and even ensured ultralow wear performance of PTFE. Trials were made also to improve the wear performance of PTFE by using carbonaceous nanofillers such as carbon nanotube (CNT) [8] and graphene [9][10]. Graphene and its derivatives proved to be very attractive self-lubricating materials themselves to achieve low friction and low wear rates [11].…”

Preparation of PTFE/graphene nanocomposites by compression moulding and free sintering: A guideline

“…showed that expanded graphite combined with other nanofillers give a synergistic effect to improve the mechanical properties of PTFE composites. However, there exists limited information regarding PTFE composites filled with graphene nanoplatelets and how it influences the physical properties of the PTFE . Furthermore, the proper fabrication methods of these nanocomposites are also relatively unestablished and very few articles address the preparation of nanofilled‐PTFE composites.…”

“…However, there exists limited information regarding PTFE composites filled with graphene nanoplatelets and how it influences the physical properties of the PTFE. 5,7,9,10 Furthermore, the proper fabrication methods of these nanocomposites are also relatively unestablished and very few articles address the preparation of nanofilled-PTFE composites. Most of the guidelines are provided by the manufacturers recommending the correct processing conditions regarding preform pressures and the sintering cycles for filled and unfilled PTFE.…”