GB/T 9871-2008 "Determination of aging performance of vulcanized or thermal plasticity rubber, tensile stress relaxation test" specifies three different test methods for evaluating the aging performance of vulcanized rubber. Method A is used for measurement under continuous strain conditions, Method B is suitable for measurement under intermittent strain conditions, and Method C is an alternative method under intermittent strain conditions. In these methods, stress at aging temperature is recorded using a stress relaxer to determine the aging behavior of the rubber. These tests can be used for quality control, thermal aging evaluation, and long-term performance prediction. The standard also includes relevant calibrating requirements and indicates applicability between different methods.