Drilling tool with elastomer seal having graded properties

摘要

A subterranean drill tool has a seal gland formed between a rotating and a static surface. An annular elastomeric seal is located in the gland in engagement with each of the surfaces. A property gradient is formed in at least part of the elastomeric material. The property gradient defines a property that changes from a first level at the surface to a second level in the interior of the seal. The elastomeric material within the property gradient has the same chemical composition as the rest of the seal.