ABSTRACT Typical seal immersion testing in lubricants does not aerate the lubricant as typically seen during normal operation of a transmission or axle. This paper will discuss a new test apparatus that introduces air into transmission fluids and gear oils during seal immersion testing. The seal materials selected for the testing are from current vehicle applications from several different material families. The test results compare the standard properties: change in tensile strength, elongation, hardness, and volume swell. Several tests were completed to investigate and refine the new testing method for seal compatibility testing with transmission fluids and gear oils. Initial results from the first data sets indicate that lubricant aeration helps improve test repeatability. In addition to aeration, the test results explore appropriate fluid immersion temperature for repeatability and appropriate test duration. INTRODUCTION Seal immersion testing is used commonly in the automotive industry to screen for compatibility issues between elastomer materials and lubricants. It is important that the two work as a system to provide adequate protection from leakage. In this study, we focused on studying transmission and axle applications. The typical process for immersion testing is described in ASTM D471 [ 1]. The standard method has been to measure elastomer properties after soaking in a lubricant at a specified temperature for a specified period of time depending on the application and the preference of the tester. The elastomer properties (tensile strength, elongation, hardness, and volume swell) are measured before and after soaking to understand any deterioration in properties. Typical soaking is done in a test tube of fluid with no aeration to the fluid, but in typicaltransmission and axle operation the fluid is aerated. The new test method aerates the fluid during the immersion test to more closely resemble transmission and axle operation. METHOD The GM Aerated Seal Test is a variation of a typical seal immersion test. Typical immersion testing consists of a standard elastomer coupon soaked in static fluid at a given temperature for a given amount of time. The elastomer properties (volume, hardness, tensile strength, and elongation) are measured before and after soaking to determine how the properties change with a given fluid. For the purpose of this study, a few elastomers (see table 1 for description) commonly used in transmissions and axles were selected and soaked in commercially available transmission fluid and gear fluid as appropriate. The major difference in this test as compared to standard immersion testing is the glassware that allows the lubricant to be aerated. The glassware is from ASTM D6594 [ 3]. The elastomer coupons are hung inside the test tube and immersed in fluid. Air is blown through the air inlet tube at five liters per minute to aerate the fluid. Figure 9 in Appendix B is a diagram of the setup, and Figure 10 is a picture of an example. The details of the final test procedure were determined based on the results presented in the “Results and Discussion” section below. The test is run for 504 hours with five liters per minute of air flow at 150°C for transmission fluids, and 125°C for gear fluids. For one test, each property is tested on eight individual coupons and averaged for the final test result. For example, in one test tube eight coupons are soaked for the purpose of measuring end of test elongation. The final reported value is the average of the eight individual coupon results. Each of the four elastomer properties are tested and calculated with the same method. One test tube can hold eight coupons to help reduce any variability seen from test tube to test tube. Seal Testing in Aerated Lubricants2011-01-1209 Published 04/12/2011 Joan Petit, Roy Fewkes and Cheryl O'Brien General Motors Company Copyright © 2011 SAE International doi:10.4271/2011-01-1209Downloaded from SAE International by Uni