3M™ Aerospace Sealant AC-770 Class B are fast cure, low density two-component, manganese dioxide cure, polysulfide fuselage sealants. 3M™ AC-770 Class B Sealants have outstanding resistance to aviation gasoline and jet fuel, as well as resistance to chemicals and petroleum products common to the aircraft industry. 3M™ AC-770 Class B Sealants maintain flexibility and bond strength on most metal substrates such as; aluminum, titanium, steel, stainless steel, and many coatings under extremes of temperature, weathering and stress. The mixed compound is a thixotropic paste easily applied by extrusion, injection gun or spatula, and exhibits superb tooling properties.
Unit of Measure

Typical Physical and Application Properties

Base Color

N/A Off-White

Accelerator Color

N/A Brown

Mix Ratio (By Weight)

N/A 100 Base/10 Accelerator

Non-Volatile Content

N/A 98.5 %

Base Viscosity

N/A 9,500 to 13,000 Poise

Note for Typical Physical and Application Properties

N/A The technical information and data should be considered representative or typical only and should not be used for specification purposes.

Application Life and Cure Time at 77 Degree Fahrenheit (ºF) and 50 Percent (%) Relative Humidity

Extrusion Rate at Application Life

N/A 88 gpm


N/A B-1 B-2

Minimum Application Life for Class B-1

N/A 1 hour

Minimum Application Life for Class B-2

N/A 2 hour

Note for Minimum Application Life

N/A Application life refers to the length of time that mixed compound remains at a consistency suitable for application with spatula or caulking gun. Application life is always measured at a standard temperature of 77 ºF with a relative humidity level of 50 %. In general, for every 20 ºF rise in temperature, the application life is halved; and for every 20 ºF drop, it is doubled. High humidity levels, greater than 65 %,during the mixing process will shorten application life.

Typical Tack-Free Time for Class B-1

N/A 3 to 4 hour

Typical Tack-Free Time for Class B-2

N/A 7 to 8 hour

Note for Typical Tack-Free Time

N/A Tack-free time is the length of time after which a mixed sealant will no longer tightly adhere to LP-P-690 standard low density polyethylene film.

Typical Cure Time for Class B-1

N/A 5 to 6 hour

Typical Cure Time for Class B-2

N/A 9 to 11 hour

Note for Typical Cure Time

N/A Cure time is defined as the length of time it takes 3M™ Aerospace Sealant AC-770 Class B 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 ºF.

Typical Physical and Performance Properties of Cured Compound after 14 Days at 77 Degree Fahrenheit (ºF)/50 Percent (%) Relative Humidity


N/A Dark Brown

Specific Gravity

N/A 1.10


N/A 42 to 48 Shore "A"

Low Temperature Flexibility

N/A No cracking, checking or adhesion loss when tested at -65 ºF (-54 ºC)

Service Temperature

N/A -65 to +250 ºF-54 to +121 ºC


N/A None


N/A 34 piw/100 % Cohesive Failure


Industry Focus

N/A Aerospace

Relative Humidity

N/A 50 %

Substrate Material

N/A Aluminum Stainless Steel Steel Titanium


N/A Polysulfide


N/A Filling Voids Sealing Fuselages

Health and Safety Precaution

Health and Safety Precaution

N/A 3M™ Aerospace Sealant AC-770 Class B are 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.



N/A The shelf life of 3M™ Aerospace Sealant AC-770 Class B is 9 months from date of packaging, when stored at temperatures below 80 ºF in its original container.

Mixed 3M™ AC-770 Class B Sealants may be stored under refrigeration as follows:
  • 15 days at -10 ºF
  • 30 days at -40 ºF
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 1/2 hour application time.

Technical Information

Technical Information

N/A The technical information, recommendations and other statements contained in this document are based upon tests or experience that 3M™ believes are reliable, but the accuracy or completeness of such information is not guaranteed.

Product Use

Product Use

N/A Many factors beyond 3M™'s control and uniquely within user's knowledge and control can affect the use and performance of a 3M™ product in a particular application. Given the variety of factors that can affect the use and performance of a 3M™ product, user is solely responsible for evaluating the 3M™ product and determining whether it is fit for a particular purpose and suitable for user's method of application.

Warranty, Limited Remedy, and Disclaimer

Warranty, Limited Remedy, and Disclaimer

N/A Unless an additional warranty is specifically stated on the applicable 3M™ product packaging or product literature, 3M™ warrants that each 3M™ product meets the applicable 3M™ product specification at the time 3M™ ships the product. 3M™ makes no other warranties or conditions, express or implied, including, but not limited to, any implied warranty or condition of merchantability or fitness for a particular purpose or any implied warranty or condition arising out of a course of dealing, custom or usage of trade. If the 3M™ product does not conform to this warranty, then the sole and exclusive remedy is, at 3M™'s option, replacement of the 3M™ product or refund of the purchase price.

Limitation of Liability

Limitation of Liability

N/A Except where prohibited by law, 3M™ will not be liable for any loss or damage arising from the 3M™ product, whether direct, indirect, special, incidental or consequential, regardless of the legal theory asserted, including warranty, contract, negligence or strict liability.



N/A These products were manufactured under a 3M™ Quality Management System registered to the AS9100 standard.