AC Tech AC-251 B-2 Black Exterior Moldline & Canopy/Windshield Sealant Catalyst - With Plunger - 6 oz.

This two-part, quick curing, polysulfide based canopy and windshield sealant is formulated for sealing acrylic, glass and polycarbonate aircraft canopies and windshields. AC-251 B Black contains no solvents and does not craze. The sealant quickly cures and exhibits excellent adhesion and resistance to UV and weather exposure.

AC-251 Class B Black has a thixotropic, non-sag consistency. It can be readily applied with a spatula or extrusion gun on vertical surfaces.

Applications

• Canopy and windshield sealant
• Exterior moldline applications

Please note, this is the catalyst component only. We also have AC Tech AC-251 B-2 Black Moldline & Canopy/Windshield Sealant Base Component available.

Two-Part Sealant Cartridges

1. Holding the cartridge, grasp the dasher rod and pull back approximately one inch.
2. 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.
3. Repeat steps 1 and 2 until all the contents of the rod are emptied into the cartridge. Remove the ramrod.
4. Mix for the required number of strokes (hand mixing) or for the required amount of time (machine mixing) indicated in the kit instructions.
5. When mixing is complete, remove bottom cap.
6. Pull the dasher rod back to the neck of the cartridge, grasp the cartridge firmly at the neck, unscrew the dasher rod and remove.
7. 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-251 Class B Black is 9 months from date of packaging, when stored at temperatures below 80°F in its original container. Pre-mixed and frozen sealant has a shelf life dependent upon the storage temperature. Mixed AC-251 Class B Black may be stored under refrigeration as follows:

15 days at -10°F
30 days at -40°F

It is important to remember that freezing, storing and thawing procedures reduce application life. In addition, 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 1/2 hour application time.

MAT-645 - Qualified (B-1/2, B-1, B-2)
TAPS 1123 - Qualified

Typical Physical and Application Properties Color Base Accelerator Final Black Black Black Mixing Ratio 100 base / 10 accelerator (by weight) Nonvolatile Content 98% Base Viscosity (Brookfield #7 Spindle @ 2 rpm) 9,000 - 14,000 poise

Application Life and Cure Time Min. Application Life* Typical Tack-Free Time** Typical Cure Time*** Tested at 77°F, 50% R.H. B-1/2 1/2 hour <3 hours 4 hours B-1 1 hour 5 hours 7 hours B-2 2 hours 8 hours 9 hours

* Application life refers to the length of time the mixed compound remains at a consistency suitable for application with spatula or caulking gun. Application life is always measured as a standard temperature of 77°F with a relative humidity of 50%. In general, for every 20°F rise in temperature, the application life is halved; and for every 20°F 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-609 standard low density polyethylene film.

*** Cure time is defined as the length of time it takes AC-251 Class B Black sealant to reach 30A hardness. It depends on three factors: remaining application life, temperature and relative humidity. The temperature/humidity factors for application life also apply to curing. To accelerate the curing process, apply heat up to (but not more than) 160°F. If the humidity is low, increasing the humidity will cure the sealant more quickly.

Typical Physical and Performance Properties* Color Black Specific Gravity 1.59 Hardness 55 Shore "A" Low Temperature Flexibility No cracking, checking or adhesion loss when tested at 65°F (-54°C) Service Temperatures -65° to +250°F (-54° to +121°C) Intermittent Exposure To 360°F (182°C) Thermal Rupture Resistant Does not blister or sponge Corrosion None Repairability 35 piw to itself and other AMS-S-8802 qualified sealants Weight Loss & Flexibility No cracking when bent 180° over a 1/8" mandrel. No more than 6% loss of the sealant compound after fluid immersion Fungus Resistance Meets MIL-STD-810 requirement Crazing No effect or acrylic or polycarbonate

* Of cured compound after 14 days @ 77°F/50% RH when tested per AMS-S-8802