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
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
With specifications requiring elastomers other than Reference Elastomers AMS 3217/2B or AMS 3217/3A, coupons cut from standard sheets (Practice D 3182
Note 48212;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
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