Measurement of the changes in the volume and hardness of an elastomer that occur from immersion in a lubricating grease or fluid provides a means for evaluating relative compatibility. Much of this test method was derived from procedures described in Test Method D 471 and Federal Test Method 791C/3603.5. In contrast to these two test methods, which emphasize the evaluation of rubber and rubber-like compounds, Test Method D 4289 was developed specifically to evaluate lubricating greases and fluids, especially those used in automotive applications, although the test method can be applied to lubricants used in industrial applications as well. Excepting the Shore Durometer A, this test method requires no specialized, rubber-testing equipment. Virtually all other equipment and supplies specified in the procedure are stock items in lubricants laboratories.

The volume and hardness-change values determined by this test method do not duplicate similar changes that occur in elastomeric seals under actual service conditions. However, they can be correlated in many instances. In one such instance, the volume-change values determined by the antecedent of this test method correlated (r ² = 0.99) with those that occurred during a vehicle test. Because of wide variations in service conditions and differences in grease and elastomer formulations, correlations between the results obtained with this test method and particular applications should be determined on an individual basis.

When the optional Reference Elastomers AMS 3217/2B (acrylonitrile-butadiene, NBR-L) and AMS 3217/3A (chloroprene, CR) are used to evaluate compatibility, the results can be used to judge a service characteristic of lubricants. In this respect, this test method is useful for lubricant specifications (for example, Specification D 4950). Similarly, this test method can be used in specifications for lubricating fluids as well.

With specifications requiring elastomers other than Reference Elastomers AMS 3217/2B or AMS 3217/3A, coupons cut from standard sheets (Practice D 3182) should be used. When the preparation of such coupons is not feasible, or the lubricant specification requires the use of rubber products that do not have a suitable size or configuration for use in preparing coupons for testing (Practice D 3183), this test method can be used as a guide for evaluating compatibility.

Note 4—Inasmuch as the precision values apply only to the elastomers specified in Annex A1 of Test Method D 4289, when a lubricant specification requires some other elastomer, the user and supplier of the lubricant should agree to the values of acceptable precision. Such values may or may not be the same as those of Test Method D 4289. It is recommended that the agreed upon precision values be stated in the user's lubricant specification.

The results of this test method are most applicable to the use of lubricating greases and fluids in contact with elastomeric seals, boots, O-rings, and similar products, where the physical demands on the elastomer are not extreme. In critical applications where the lubricant will be in contact with rubber parts subject to severe flexing, extreme temperatures, or similar stresses, other rubber properties, such as tensile strength and elongation, should also be evaluated as they may be more indicative of the true compatibility characteristics.

1.1 This test method evaluates the compatibility of lubricating greases and fluids with coupons cut from standard elastomer sheets (Practice D 3182) or, optionally, from SAE Specification AMS 3217/2B (NBR-L) and AMS 3217/3A (CR) sheets. Compatibility is evaluated by determining the changes in volume and Durometer A hardness that occur when elastomer coupons are totally immersed in a lubricant sample for 70 h at either 100 or 150°C or as required by the lubricant specification.

1.1.1 Some lubricant specifications may require different test conditions, such as longer durations or lower or higher temperatures. In such instances, the repeatability and reproducibility values stated in Section 12 do not apply, and the user and supplier should agree on acceptable limits of precision.

Note 1—The scope of this test method now includes the evaluation of the elastomer compatibility of both lubricating fluids and greases. Testing of fluids was not included in Test Method D 4289–95 and earlier versions.

1.2 This test method can also be used as a guide to evaluate the compatibility of greases with rubber products not in standard sheet form (Practice D 3183).

1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.3.1 Exception—When listed, Durometer A units shall be regarded as the standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.For specific warning statements, see 8.4-8.6.