MIL-S-83318 Sealing Compound, Low Temperature Curing, Quick Repair Integral Fuel Tanks And Fuel Cell Cavities S/S By Sae-Ams-S-83318This specification covers a two component, temperature??resistant ??65??F to +250??F ??54??C to +120??C, low temperature 20??F minimum curing synthetic rubber compounds for quick repair of aircraft integral fuel tanks and fuel cell cavities. During application, the sealing compounds shall be a suitable, fluid consistency.

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MIL-S-83318A(USAF)

4.9 Test methods

4.9.1 Specific gravity. Three test specimens approximately 0.125 x 1 x 1 inch (3.2 x 25.4 x 25.4 mm) in size shall be cut out with a sharp razor blade from a sheet of the sealing compound that has been cured as specified in 4.7.6. Determine the specific gravity of each sample in accordance with ASTM D 792, method A and report the average value.

4.9.2 Nonvolatile content. Within 5 minutes after mixing, 11 to 12 grams of mixed sealing compound shall be transferred as rapidly as possible to a previously weighed (W1) aluminum dish approximately 2 inches (50 mm) in diameter. The Class A sealant shall be poured into the dish. The Class B sealant shall be extruded from a plastic cartridge fitted with a 0.125 inch (3.18 mm) orifice nozzle, filling the bottom of the dish to a uniform depth. The initial weight (W2) shall be determined using an analytical balance accurate within +1 mg. Immediately following weighing, the sample and dish shall be placed in a circulating air oven pre-heated to 160°F (70°C), and allowed to dwell for 168 +2 hours (7 days).

Following this, the sample and dish shall be removed from the oven and allowed to cool in a

desiccator for 1 hour. Final weight (W3) shall be determined on the same balance used for initial weights. All weights shall be recorded to the nearest milligram.

Percent nonvolatile shall be determined from the average of three (3) samples calculated as follows:

(W3 - W1)

Percent Nonvolatile = x 100

W2 - W1

4.9.3 Viscosity of base compound. The viscosity shall be determined with base compound placed in a pt. (1/2 L) can. The can shall be filled with base compound to within 1/2 inch (12 mm) of the top, covered and stored at 77°F (25°C) for not less than 8 hours. The base compound shall then be thoroughly mixed by stirring slowly for not less than 3 minutes after which the can shall then be closed and the base compound shall be allowed to stand for

not less than 1 hour. The Brookfield Model RVF viscosimeter, or equal, shall be used. The readings obtained shall be converted to poises. Pa.s) For Class A material, the No. 6 spindle at 10 revolutions per minute (rpm) shall be used for the test. For Class B material, the No. 7 spindle at 2 rpm shall be used. The highest reading shall be taken after the instrument has run in the base compound for not less than 1 minute.

4.9.4 Flow (class B only). A standard sealant gun cartridge, fitted with a suitable nozzle, shall be filled with freshly mixed sealing compound. The gun and sealing compound shall be maintained at standard conditions throughout the test. The test shall be conducted with a flow-test fixture as shown on figure 1 and under flow conditions specified in 3.3.4. Depth of plunger tolerance is critical and shall be controlled within the tolerance during all tests. The flow-test fixture shall be placed on a table with the front face upward and plunger depressed to the limit of its travel.