| 摘要 |
A dynamic O-ring seal for retaining the lubrication around a rock bit bearing for drilling subterranean formations has a composition comprising 100 parts by weight highly-saturated nitrile elastomer, furnace black in the range of from 40 to 70 parts by weight, peroxide curing agent in the range of from 7 to parts by weight, graphite in the range of from 10 to parts lay weight, zinc oxide or magnesium oxide in the range of from 4 to 7 parts by weight, stearic acid in the range of from 0.5 to 2 parts by weight, and sufficient plasticizer to provide a Shore hardness no more than A 80.
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