Influence of crosslinking density on the tribological behavior of norbornene-based polymeric materials

In this study, the friction and the wear behavior of norbornene-based polymers prepared by ring-opening metathesis polymerization (ROMP) reaction are evaluated as a function of the crosslinking density. Tribological measurements were performed using a ball-on-flat reciprocating microtribometer. Friction and wear experiments under dry sliding were evaluated using a 1.2 mm radius Si3N4 spherical probe as well as a 100 μm radius conical diamond probe with a 90° cone angle. Wear experiments were conducted at constant normal loads for 100–500 reciprocating cycles. Wear depths were estimated from wear grooves using a contact profilometer, and scanning electron microscopy was used to elucidate deformation mechanisms in the various samples. Correlation between the crosslinking density and the wear behavior were observed.

Research highlights
► The tribological properties of ring opening metathesis polymerization (ROMP) thermosetting polymers have been evaluated as a function of crosslinking density.
► Both the friction and wear against a spherical Si3N4 and a conical diamond probe were affected by crosslinking.
► The material without the crosslinker (CL-0) showed the highest friction coefficient against Si3N4.
► Reciprocating wear tests have confirmed that all materials, except CL-0, show resistance to wear against Si3N4 under the given loading conditions.
► All samples exhibited abrasive wear by the sharp diamond probe.
► The abrasive wear depth was observed to decrease with increasing crosslinking density.