ASTM D7216 Standard Test Method for Determining Automotive Engine Oil Compatibility with Typical Seal Elastomers
8. Procedure
8.1 General Background - Conduct the immersion tests for any non-reference oil(s) on the basis of a test series operation. A test series is a complete evaluation program, using the specified physical tests, for any selected number of non-reference oils and the reference oil using one or more of the reference elastomers. Use the same elastomer batch for both non-reference oils and the reference oil.

8.2 Number of Test Specimens - There are two types of test specimens: dumbbells for tensile testing and 25 by 50 mm (1 by 2 in.) rectangular sheets for mass measurements and hardness testing. For each elastomer/oil combination to be tested cut: (1) twelve dumbbell specimens (six for initial and six for final tensile testing); (2) six rectangular specimens (each specimen is used for both initial and final volume/hardness testing). Ensure that all reference elastomer specimens for a test series are cut from the same elastomer batch.

8.3 Test Specimen Preparation - Determine the number of elastomer reference sheets required for the projected testing. For each elastomer, this number will depend on the number of oils involved and the number of test specimens required (see 8.2). Condition these sheets for at least 3 h at 23 +/- 2°C as specified in Test Method D412. Ensure cutting dies are sharp; see Test Method D412 for additional information on die maintenance.
8.3.1 Specimens for Tensile Testing - From each reference elastomer, cut the required number of dumbbell specimens from the 2 mm thick sheets, using Die C as specified in Test Method D412, with the long axis of the dumbbell parallel to the grain. (The direction of the grain is marked on the sheets as noted in footnote A to Table A1.1.) Using a die press for the operation, cut only one sheet thickness at a time. Depending on the number of oils being evaluated, two or more sheets will be required for each elastomer. Each sample of six dumbbells (initial and final sample sets) shall contain as close as possible an equal number of dumbbells from each of the individual sheets as required for the testing.

8.3.2 Specimens for Mass Measurements Required for Volume Determination - Cut the required number of 25 by 50 mm rectangular specimens from the 2-mm thick sheets. Because two or more sheets will be required (to prepare at least twelve specimens; six for at least one non-reference oil and six for the reference oil) for the total number of specimens for any elastomer, each sample of six shall contain an equal number of specimens from each of the individual sheets as required for the testing.

8.3.3 Specimens for Hardness Testing - Use the specimens prepared for the mass measurements (see 8.3.2).

8.4 Measurement of the Pre-Immersion Elastomer Properties - Measure the initial tensile properties, hardness and mass, as described in 8.4.1 to 8.4.3, of the pre-immersion specimens. Note that while the pre- and post-immersion specimens are different for the tensile measurements they are the same for the mass and hardness measurements. Ensure, therefore, that the mass and hardness are measured preimmersion.
8.4.1 Tensile Measurements - Using the procedure specified in Test Method D412, test six dumbbells for each oil/elastomer combination, recording for each dumbbell the ultimate elongation and the tensile strength. To eliminate effects of variations in ambient conditions such as temperature and humidity, measure the initial tensile properties in the same time frame as the final tensile proprieties, that is, post-immersion (see 8.6.1).

8.4.2 Hardness - To protect the equipment, it is recommended that the hardness measurements be carried out before the mass measurements to ensure the Durometer tip is kept dry. Stack three 25 by 50 mm specimens on top of each other to obtain the requisite minimum 6-mm thickness. For ease of reference, the specimens at the top, middle and bottom of the stack will be referred to as Specimens A, B, and C, respectively. In accordance with Test Method D 2240, determine the Durometer A hardness of the elastomer specimens, taking readings 1 +/- 0.1 s after the pin makes contact with the rubber. Make repeat measurements on different parts of the specimen. The following readings are taken: Take three readings from the top side of Specimen A. Turn Specimen A over and take three additional readings from its other side. Calculate and report the arithmetic mean of the six values. Move Specimen C to the top of the stack and take another set of six readings as described in Move Specimen B to the top of the stack and take another set of six readings as described in Prepare a second stack of three specimens and repeat to

8.4.3 Measurement of Mass - For each elastomer/oil combination, measure and record the mass, to the nearest mg, of each of the six 25 by 50 mm rectangular specimens in air and water using the water displacement method. With a leather punch or cork borer, punch or cut a 2 to 5-mm (0.08 to 0.20-in.) diameter hole near the center of a short edge. Corners or small radiused notches can be cut for identification; do not cut V-notches. Weigh the specimen in air to determine M1 (if it is pre-immersion) or M 3 (if it is post-immersion). Using the hole in its short edge, suspend the elastomer test specimen from the hanger wire. Immerse each specimen in a beaker of the wetting agent solution to remove air bubbles from the surface. Dislodge any air bubbles by agitating the specimen while in the solution. Suspend the hanger wire and specimen from the balance hook. Inspect the submerged specimen and remove any adhering air bubbles. If the bubbles are difficult to remove, repeat In uncommon instances, it may be necessary to devise a means of mechanically dislodging adherent air bubbles. Weigh the specimen in water to determine M2 (if it is pre-immersion) or M4 (if it is post-immersion).

8.5 Immersion Testing - Conduct all immersion tests for a test series concurrently in the same heated immersion test bath or block.
8.5.1 Pour 150 +/- 5 mL of test oil into the immersion test tubes. Four test tubes are required for each elastomer/oil combination. In each tube, suspend three rectangular specimens or three dumbbell specimens from the stainless steel wire hanger, as shown in Fig. 1. Locate inert (to oil or rubber) spacers 1 to 2 mm thick (such as stainless steel washers) between each test specimen to prevent specimens from touching each other or the test tube wall (see Fig. 2). Cover each test tube with a stopper as specified in 6.5.

8.5.2 Set the heating block/bath temperature to the appropriate value for the elastomer under test. (Table 1 shows the immersion test temperatures and immersion times to be used for the four reference elastomers.) When the test temperature has been attained, insert the test tubes into the heating block/bath. To minimize effects of temperature variations within the heating block/bath, spread the tubes randomly, avoiding placing all the tubes in the same portion or putting tubes containing the same samples together. Ensure that no specimen touches another specimen or the test tube wall. Such an occurrence invalidates the test. To ensure that aging conditions are equivalent for both non-reference and reference oils, insert all tubes in the heating block/bath within 8 h of each other. Each tube shall be in the block/bath for the period specified in Table 1. The time starts when a tube is inserted in the heating block/bath, provided the latter is already at the correct temperature. If desired, as a check, insert a dummy tube containing an appropriate amount of oil and measure its temperature.

8.5.3 At the end of the aging period, remove the specimens from the test tubes and place them (while on the suspension wire) on a clean, absorbent towel or surface to cool to ambient temperature. The cooling period shall not exceed 30 min. If necessary, increase the cooling rate by placing the specimens on a surface that allows cooling from both sides.

8.5.4 At the end of the cooling period, remove the specimens from the suspension wire and place them on a new, clean, absorbent towel or surface. Remove the excess oil with a clean absorbent towel. Begin the final testing 30 to 60 min after removal of the specimen from the test tube. Take no more than 2 h to complete this final testing.

8.6 Measurement of Post-Immersion Physical Properties:
8.6.1 Using the procedure described in 8.4.1, measure the tensile strength and ultimate elongation of both the pre- and post-immersion specimens.

8.6.2 Measure the hardness and the mass in air and water of the post-immersion specimens using the procedures described in 8.4.2 and 8.4.3, respectively.

9. Calculations
9.1 For each combination of reference elastomer/test oil calculate the change in properties as follows:

NOTE 5 - A negative change indicates a reduction in performance after immersion in the oil. For the hardness change, negative and positive changes indicate that the specimen softened or hardened, respectively.

9.1.1 Ultimate Elongation Change:
ΔE = 100 [(Ef - Ei)/Ei]
ΔE = ultimate elongation change, %,
Ei = initial ultimate elongation, %, and
Ef = final ultimate elongation, %.

9.1.2 Tensile Strength Change:
ΔTS = 100 [(TSf - TSi)/TSi]
ΔTS = tensile strength change, %,
TSi = initial tensile strength, MPa (lbf/in.2), and
TSf = final tensile strength, MPa (lbf/in.2).

9.1.3 Volume Change:
ΔV = 100 [{(M3 - M4) - (M1 - M2)}/(M1 - M2)]
ΔV = volume change, %,
M1 = initial mass in air, g,
M2 = initial mass in water, g,
M3 = final mass in air, g, and
M4 = final mass in water, g.

9.1.4 Durometer A Hardness Change:
ΔH = (Hf - Hi)
ΔH = hardness change, Durometer A units,
Hi = initial hardness, Durometer A units, and
Hf = final hardness Durometer A units.

10. TMC 1006-1 Reference Oil Testing
10.1 As specified in 8.1, the reference oil TMC 1006-1 is evaluated simultaneously with each set of non-reference oil tests.

10.2 Prior to conducting a reference oil test, procure a supply of TMC 1006-1 directly from the TMC. Each reference oil sample is identified using a unique set of identification codes on the container labels.

10.3 Report the results of the TMC 1006-1 reference oil tests to the TMC (see Section 11).
10.3.1 Transmit reference oil test data to the TMC by electronic means or by telephone facsimile immediately upon completion of the test analysis. Include all of the reporting forms in the transmission.

NOTE 6 - Specific protocols for the electronic transmission of test data to the TMC are available from the TMC.

10.4 Evaluation of Reference Oil Test Results - Upon receipt of the transmitted test results for TMC 1006-1, the TMC will review the test for operational adherence to the published test method.
10.4.1 If the test is found to be operationally valid, the reference oil results will be evaluated by the TMC using acceptance criteria established by the Elastomer Test Surveillance Panel. The reference oil acceptance criteria are subject to change at the discretion of this Panel.

10.4.2 In the event the TMC find the reference oil test results are unacceptable, an explanation of the problem relating to the failure will be provided to the testing laboratory. If there is an obvious operational reason for the failed test, correct the problem before carrying out another test series. If the reason for failure is not obvious, re-check all test-related equipment for compliance to the test method and good laboratory practice.

10.5 Status of Non-reference Oil Tests Relative to TMC Reference Oil Test - The batch of non-reference oil tests is considered valid only if the TMC inform the testing laboratory that results reported for the reference oil are acceptable.