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AC-236 Class A (NSN-8030-00-965-2004) is a brushable, two-component, liquid polysulfide polymer system providing excellent fuel tank and fuselage seals. It has outstanding resistance to aviation gasoline and jet fuel, as well as resistance to chemicals and petroleum products common to the aircraft industry. AC-236 Class A maintains its flexibility and bond strength on most metal substrates like aluminum, stainless steel, steel, and many coatings under extremes of temperature, weathering and stress. The mixed compound is a pourable liquid easily applied by brush. It has excellent tooling properties. Applications include sealing integral fuel tanks, repairing integral fuel tanks and sealing fuselages.
Applications:
- Sealing integral fuel tanks
- Repairing integral fuel tanks
- Sealing fuselages
Specifications:
- AMS-S-8802 - Qualified
- LES 1039 BU - Qualified
- BS 4657 - Qualified
- BS 25146 - Qualified
- Typical Physical Application Properties
- Color: Base - White, Accelerator - Black
- Mix Ratio: 100 base / 10 accelerator (by weight)
- Nonvolatile Content: 87%
- Base Viscosity (RVF Brookfield #6 spindle @ 10rpm, 77 degrees F): 300 poise
Typical Physical and Performance Properties of Cured Compound After 14 Days at 77 degrees F / 50% Relative Humidity (when tested per AMS-S-8802):
- Color: Gray
- Specific Gravity: 1.64
- Hardness: 60 Shore "A"
- Low Temperature Flexibility: No cracking, checking or adhesion loss when tested at -65 degrees F (-54 degrees C)
- Service Temperatures: -65 degrees F to +250 degrees F (-55 degrees C to +121 degrees C)
- Thermal Rupture Resistance: Retains pressure of 10 psi at 250 degrees F with negligible deformation
- Corrosion: None
- Repairability: 40 piw to itself and other MIL-S-8802 qualified sealants
- Weight Loss and Flexibility: No cracking when bent 180 degrees over a 1/8" mandrel. No more than 6% loss of the sealant compound after fluid immersion
Application Life and Cure Time (At 75 degrees F, 50% relative humidity):
Minimum Application Life:
A-1/2: 1/2 hour
A-2: 2 hours
Typical Tack-Free Time:
A-1/2: 7 hours
A-2: 24 hours
Typical Cure Time:
A-1/2: 24 hours
A-2: 48 hours
Application Life refers to the length of time that mixed compound remains at a consistency suitable for application with roller or brush. Application life is always measured at a standard temperature of 75 degrees F with a relative humidity level of 50%. In general, for every 20 degrees F rise in temperature, the application life is halved; and for every 20 degree drop, it is doubled. High humidity levels during the mixing process will shorten application life.
Tack-free Time is the length of time after which a mixed sealant will no longer tightly adhere to L-LP-690 standard low density polyethylene film.
Cure time is defined as the length of time it takes AC-236 Class A sealant to reach 30A hardness. It depends on three factors: remaining application life, temperature and relative humidity. To a certain extent, the temperature/humidity factors for application life also apply to curing. To accelerate the curing process, apply heat up to (but not more than) 120 degrees F.
Typical Values of AC-236 Class A to AMS-S-8802
Peel Strength (Specification requirement - 20 lbs. / 100%, wire mesh) Substrate MIL-S-5059
Conditioning:
7 days at 140 degrees F in JRF = 53 lbs/ / 100% (Average Peak Load / % Cohesion)
7 days at 140 degrees F in JRF/SW = 63 lbs. / 100% (Average Peak Load / % Cohesion) Substrate MIL-C-27725
Conditioning:
7 days at 140 degrees F in JRF = 53 lbs/ / 100% (Average Peak Load / % Cohesion)
7 days at 140 degrees F in JRF/SW = 63 lbs. / 100% (Average Peak Load / % Cohesion) Substrate MIL-P-23377
Conditioning:
7 days at 140 degrees F in DI Water = 63 lbs/ / 100% (Average Peak Load / % Cohesion)
7 days at 140 degrees F in Salt Water = 63 lbs. / 100% (Average Peak Load / % Cohesion)
Mixing Instructions for Two-Part Sealant Cartridges:
Holding the cartridge, grasp the dasher rod and pull back approximately one inch. Insert the ramrod into the hollow of the dasher rod, break the piston loose, and inject about 1/3 of the contents into the cartridge. Note: Do not inject all of catalyst in one location. Distribute evenly throughout base material. Repeat steps 2 and 3 until all the contents of the rod are emptied into the cartridge. Remove the ramrod. Mix for the required number of strokes (hand mixing) or for the required amount of time (machine mixing) indicated in the kit instructions. When mixing is complete, remove bottom cap. Pull the dasher rod back to the neck of the cartridge, grasp the cartridge firmly at the neck, unscrew the dasher rod and remove. Screw the nozzle into the cartridge, insert into the extrusion gun and use as required. For hand extrusion, press the used dasher rod against the plunger to force the material from the cartridge Storage:
The shelf life of AC-236 Class A is 9 months from date of packaging, when stored at temperatures below 80 degrees F in its original container. Mixed AC-236 Class A may be stored under refrigeration as follows: 15 days at -10 degrees F, 30 days at -40 degrees F. It is important to remember that freezing, storing and thawing procedures reduce application life. Also, frozen storage will reduce application life by varying amounts depending on the storage temperature and length of storage time. All aspects of storage, freezing and thawing should be planned carefully and it is not recommended to mix and freeze with less than half an hour application time. |
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