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3M Aerospace AC-251 Class B Canopy & Windshield Sealant

3M Aerospace AC-251 Class B Canopy & Windshield Sealant

3Mô Aerospace Sealant AC-251 Black Class B are two-part, quick curing, polysulfide based canopy and windshield sealants. These products are formulated for sealing acrylic, glass, and polycarbonate aircraft canopies and windshields. 3M AC-251 Black Class B Sealants contain no solvents and do not craze. The sealants quickly cure and exhibit excellent adhesion and resistance to UV and weather exposure.

3M AC-251 Black Class B Sealants have a thixotropic, nonsag consistency. They can be readily applied with a spatula or extrusion gun on vertical surfaces.

Use Instructions
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 2 and 3 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 degrees F in its original container.

Mixed AC-251 Class B Black 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.

Health and Safety Precautions

AC-251 Class B Black sealant is safe to use and apply when recommended precautions are followed. Before using this product, read and understand the Material Safety Data Sheet (MSDS), which provides information on health, physical and environmental hazards, handling precautions and first aid recommendations. An MSDS is available on request. Avoid overexposure. Obtain medical care in case of extreme overexposure.

Features
  • Canopy and windshield sealant
  • Exterior moldline applications
  • Specifications
    MAT-645 - Qualified (B-1/2, B-1, B-2)
    TAPS 1123 - Qualified

    Typical Physical and Application Properties

  • Color: Base - Black, Accelerator - Black, Final - Black

  • Mixing Ratio: 100 base / 10 accelerator (by weight)

  • Non-volatile Content: 98%

  • Base Viscosity (Brookfield #7 Spindle @ 2rpm): 9,000-14,000 poise
  • Application Life and Cure Time
    (Tested at 77 degrees F, 50% Relative Humidity)

    B-1/2

  • Minimum Application Life*: 1/2 hour

  • Typical Tack-free Time**: less than 3 hours

  • Typical Cure Time***: 4 hours
  • B-1

  • Minimum Application Life*: 1 hour

  • Typical Tack-free Time**: 5 hours

  • Typical Cure Time***: 7 hours
  • B-2

  • Minimum Application Life*: 2 hours

  • Typical Tack-free Time**: 8 hours

  • Typical Cure Time***: 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 degrees F with a relative humidity level of 50%. In general, for every 20 degree F rise in temperature, the application life is halved; and for every 20 degree F drop, it is doubled. High humidity levels during the mxing 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-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 degrees F. If the humidity is love, increasing the humidity will cure the sealant more quickly.

    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: Black

  • Specific Gravity: 1.59

  • Hardness: 55 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 (-54 degrees C to +121 degrees C)

  • Intermittent Exposure To: 360 degrees F (182 degrees 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 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

  • Fungus Resistance: Meets MIL-STD-810 requirement

  • Crazing: No effect on acrylic or polycarbonate

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    Size
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    Spec
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    Certification
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    MSDS1
    Country of Origin: USA
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    Part Number
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    Size
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    Spec
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    MSDS1
    Country of Origin: United States
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    Size
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    Spec
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    Size
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    Spec
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    Size
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    Spec
    3M Standard, Class B-1/2
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    Size
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    Spec
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    MSDS1
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    Size
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    Spec
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