Measured as a loss percentage based on original weight, abrasion resistance is the resistance of a rubber compound to wearing away by contact with a moving abrasive surface. Whereas the cutting or nicking of a seal’s surface is an instantaneous event, abrasive rubbing or scraping is much more of a progressive phenomenon that develops over time. Seals in motion are most susceptible to abrasion. Hard compounds tend to exhibit less abrasive wear than soft compounds, but use of a harder compound can also increase friction in dynamic seals, and increased friction generates seal-degrading heat.

Because of the many potential variables (including heat fluctuation and surface contamination), abrasion resistance is hard to accurately measure. Testing typically involves the uniform application of an abrasive material (such as sandpaper) to the surface of a sample. ASTM standards describe three different abraders: D 1630 relies on a National Bureau of Standards (NBS) abrader (see Figure 21); D 2228 uses a Pico abrader (see Figure 22); and D 3389 (also known as Taber Abrasion) employs a double-head abrader and a rotary platform (see Figure 23). Regardless of the specific test method, the relative amount of sample material that is lost due to abrasion is a good indication of abrasion resistance.

Generally speaking, hydrocarbon-based elastomers tend to offer better abrasion resistance than fluorocarbon elastomers. Polyurethane offers the most outstanding abrasion resistance, while carboxylated nitrile and hydrogenated nitrile offer abrasion resistance that is superior to other hydrocarbon-based elastomers.

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