Rubber contact mechanics: adhesion, friction and leakage of seals

Abstract

We study the adhesion, friction and leak rate of seals for four different elastomers: Acrylonitrile Butadiene Rubber (NBR), Ethylene Propylene Diene (EPDM), Polyepichlorohydrin (GECO) and Polydimethylsiloxane (PDMS). Adhesion between smooth clean glass balls and all the elastomers is studied both in the dry state and in water. In water, adhesion is observed for the NBR and PDMS elastomers, but not for the EPDM and GECO elastomers, which we attribute to the differences in surface energy and dewetting. The leakage of water is studied with rubber square-ring seals squeezed against sandblasted glass surfaces. Here we observe a strongly non-linear dependence of the leak rate on the water pressure ΔP for the elastomers exhibiting adhesion in water, while the leak rate depends nearly linearly on ΔP for the other elastomers. We attribute the non-linearity to some adhesion-related phenomena, such as dewetting or the (time-dependent) formation of gas bubbles, which blocks fluid flow channels. Finally, rubber friction is studied at low sliding speeds using smooth glass and sandblasted glass as substrates, both in the dry state and in water. The measured friction coefficients are compared to theory, and the origin of the frictional shear stress acting in the area of real contact is discussed. The NBR rubber, which exhibits the strongest adhesion both in the dry state and in water, also shows the highest friction both in the dry state and in water.

Adhesion and Friction for Three Tire Tread Compounds

“…During lateral motion of the rubber block, a chain stretches, detaches, relaxes, and reattaches to the surface to repeat the cycle. The picture is schematic, and in reality, no detachment in the vertical direction is expected, but only a rearrangement of molecule segments (in nanometer-sized domains) parallel to the surface from pinned (commensurate-like) to depinned (incommensurate-like) domains, [27].…”

“…The sliding distance is measured using a distance sensor and the sliding velocity obtained by dividing the sliding distance with the sliding time. This setup can only measure the friction coefficient on the branch of the µ(v)-curve where the friction coefficient increases with increasing sliding speed v,[27].…”

Rubber friction: The contribution from the area of real contact

“…Recently, Tiwari et al 12 presented experimental results for rubber friction on sandblasted glass substrates. For this a) URL: www.MultiscaleConsulting.com.…”

Maximizing Friction by Passive Jamming

“…The rigidified granular material generates these forces by mechanical interlocking and presumably by energy dissipation due to high friction between the densely packed particles 24–29. The membrane generates friction forces by the strong deformation of the thin elastic membrane but also by adhesive interaction with the substrate 30,31. Once the normal load is removed, the granular material returns to a fluid‐like state, and so the sample can be removed easily from the substrate without requiring high pull‐off forces.…”

“…[24][25][26][27][28][29] The membrane generates friction forces by the strong deformation of the thin elastic membrane but also by adhesive interaction with the substrate. [30,31] Once the normal load is removed, the granular material returns to a fluid-like state, and so the sample can be removed easily from the substrate without requiring high pull-off forces.To study this novel friction-enhancing system, we investigate the jamming transition of the GMFP. We then characterize its friction coefficient on different clean and contaminated substrates and examine the interplay of the different physical mechanisms by developing a numerical model.…”