Method 4.4.7 is a coolant resistance test for rubber grommets. Sample material shall be immersed in ethylene glycol conforming to A-A-52624 Type I, Concentration C for 70 hours at 150 +/- 2C. The hardness shall then be determined in accordance with method 4.4.1 (using a Shore A durometer per ASTM D2240).
The hardness change after coolant immersion must not exceed the maximum specified in Table I of the standard: +/- 15 points for both Composition A (synthetic rubber) and Composition B (silicone rubber) grommets.
This test ensures that the grommet material maintains its physical integrity when exposed to engine coolant at elevated temperatures, which is critical for aerospace applications where grommets protect rods, wires, and cables passing through panels exposed to petroleum-based oils and coolants.