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 InstructionsTwo-Part Sealant Cartridges:
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.
SpecificationsMAT-645 - Qualified (B-1/2, B-1, B-2)
TAPS 1123 - Qualified
Typical Physical and Application Properties
Application Life and Cure Time
*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