Purpose

There are many tests that have been developed to characterize rubber O-rings. Many of these tests are independent of the size of the O-ring being tested. However, there are some tests, specifically, stress/strain properties, that are a function of the O-ring's size. The purpose of this report is to provide guidelines for specifying O-rings that would be considered "suitable for testing" when writing O-ring material specifications.

Background

The vast majority of O-ring specifications written to date do not specify a specific O-ring size as the appropriate test specimen. Typically, phrases like "the finished part," "if of suitable size," or " the end item" are used when conformance testing is referred to. Currently, this situation is handled by the O-ring manufacturer on a case-by-case basis through discussions with the customer. The reason why this is problematic is that physical properties can change as the O-ring size being tested changes. It should be noted that some polymer families are more sensitive to this phenomenon than others.