MIL-S-83318A(USAF)
Immediately after mixing, enough of the mixed sealing compound shall be extruded from the application gun to fill the recessed cavity of the fixture and leveled off even with the block. Within 10 seconds after the leveling operation, the fixture shall be placed on its end and the plunger immediately advanced to the limit of its forward travel. The initial flow shall be measured. The flow shall be measured from tangent to the lower edge of the plunger to the farthest point to which flow has advanced.
4.9.5 Application time method. The base compound, curing compound, and application gun shall be stabilized at standard conditions (see 4.6) for not less than 8 hours before not less than 250 g of the base compound is mixed with the proper amount of curing compound. The mixed sealing compound shall be promptly used to fill a standard sealing compound gun cartridge, having a nozzle with an orifice diameter of 0.125 +0.005 inch (3.18 +0.13 mm). The gun and sealing compound shall be maintained at standard conditions throughout the test. The gun shall be attached to a constant air supply of 90 +5 psi (600 +35 KPa). From 2 to 3 inches (50 to 75 mm) of sealing compound shall be extruded initially to clear trapped air. At the end of 1/6 hour, measured from the beginning of the mixing period, the sealing compound shall be extruded onto a previously weighed suitable receptacle for 1 minute and the weight of extruded sealing compound determined.
4.9.6 Tack-free time. An aluminum alloy test panel conforming to AMS 4049 and measuring 0.040 by 2-3/4 by 6 inches (1.0 by 70 by 150 mm) in size shall be cleaned in accordance with 4.7.1. Sealing compound applied in accordance with 4.7.5 shall cover the cleaned panel surface to a dept of 0.125 inch +0.016. The sealant shall be cured at standard conditions (see 4.7.6). At the end of the specified tack-free time (see 3.3.6), two
1-inch by 7-inch (25 by 175 mm) pieces of polyethylene film 0.005 +0.002 inch (0.10
+0.05 mm) thick shall be applied to the sealing compound and held in place using a pressure of approximately 0.5 ounces per square inch for 2 minutes. The strips shall then be slowly and evenly withdrawn at right angles to the sealing compound surface. The polyethylene shall come away clean and free of sealing compound.
4.9.7 Cure time. The instantaneous hardness shall be determined in accordance with method 3021 of FED-STD-601 after the sealing compound is allowed to cure at standard conditions as specified in 3.3.7 and table I. The reading shall be taken on a double
back-to-back 0.125 inch (3 mm) thick specimen.
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