The Frictional Properties of Plastics

“…Though studied for the past 60 years [1], and industrially utilized with success in microparticle-filled forms for nearly as long [2], the tribological behavior of polytetrafluoroethylene and particularly the wear resistance mechanisms of its microcomposites has remained a topic of debate. The recent demonstration of even further reduced wear rates down to *10 -7 mm 3 /Nm, realized by instead using nanoscale filler particles [3], warrants review of the framework through which the wear behavior of PTFE and its composites is understood.…”

Section: Introductionmentioning

confidence: 99%

Coupled Effect of Filler Content and Countersurface Roughness on PTFE Nanocomposite Wear Resistance

2009

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In tests of PTFE with 2.9% volume content alpha-phase alumina nanoparticles (40 or 80 nm) in sliding reciprocation against polished steel, wear rates of *10 -7 mm 3 /Nm were measured which is four orders-ofmagnitude lower than unfilled PTFE and two orders-ofmagnitude lower than with microparticles (0.5 or 20 lm) of more conventional filler size. This was similar to that previously reported in unidirectional sliding, and did not vary greatly with stroke of reciprocation. For a microfilled PTFE, the wear rate gradually increased towards that of unfilled PTFE as filler content was reduced, whereas nanofilled PTFE maintained relatively constant *10 -7 mm 3 /Nm to filler contents as low as 0.18% before reverting towards the rapid wear rate of unfilled PTFE. Lightly filled nanocomposites depend upon low countersurface roughness to maintain such low wear rate, and with increasing roughness the wear rate was found to transition at a critical value to a wear rate of *10 -5 mm 3 /Nm. Nanocomposites with higher filler contents were able to retain the low wear rates against rougher countersurfaces, as the critical roughness at which this wear resistance was lost tended to increase with the square of the filler content. Upon encountering extremely high countersurface roughness in the range R a = 6-8 lm, nanocomposites at each filler content eventually increased in wear rate to *10 -4 mm 3 /Nm. The steel countersurface did not appear to play an important role in the extreme wear resistance of these alumina nanofilled PTFE composites, as comparable performance was also displayed against alumina countersurfaces.

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“…Investigating a group of linear polymers such as polythene, polyvinylchloride etc., Shooter and Tabor (1952) found indeed that the friction force is approximately equal to the product of the area of contact and the shear strength of the The Friction of Solids 205 plastic in bulk. That the interface is often stronger than the softer of the two materials could be demonstrated even with polymers sliding on metals and, what is more remarkable still, a plastic such as nylon is sometimes capable of plucking out a small fragment from a hard steel surface (Rabinowicz and Shooter, 1952), thus causing some wear.…”

Section: E H Freitagmentioning

confidence: 91%

The friction of solids

Freitag

1961

Contemporary Physics

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The Frictional Properties of Plastics

Cited by 139 publications

References 7 publications

Interfacial shear strength of fiber reinforced soil

Interfacial shear strength of fiber reinforced soil

Coupled Effect of Filler Content and Countersurface Roughness on PTFE Nanocomposite Wear Resistance

The friction of solids

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