The Application Time or Standard Work Life is the number after the Class letter. For Class A and B, 1/2 equals 1/2 hour application time and 2 equals 2 hour application time.
For Class C the Application and Assembly Time conform to industry and manufacture’s specifications.
Class C Application Time
|Specification||Class Designation||Applicaton Time||Squeeze-out/Assembly time||Standard Cure @ 77°F|
|BMS 5-95||C-20||12 hours||20 hours||3 weeks|
|C-80||24 hours||48 hours||6 weeks|
|C-168||48 hours||168 hours||10 weeks|
|C-336||96 hours||336 hours||20 weeks|
|MIL-PRF-81733||Type IV-4||4 hours||8 hours||Not Applicable|
|Type IV-12||12 hours||24 hours||Not Applicable|
|Type IV-24||24 hours||48 hours||Not Applicable|
|Type IV-40||40 hours||120 hours||Not Applicable|
|Type IV-48||48 hours||168 hours||Not Applicable|
The length of time, after mixing, or the end of the thaw for PMF, the sealant remains suitable for application to the substrate. Since temperature and humidity can greatly affect this, stated application time is generally established at 77°F (25°C) and 50% relative humidity.
The length of time for a sealant to cure to a state where polyethylene film, applied with light pressure to the sealant’s surface, can be cleanly removed. A TFT condition generally occurs well after the Assembly time for a given sealant.
The length of time it takes for a sealant to cure to a certain minimum hardness as determined by the procuring specification. This is not the final cure hardness for the sealant, but indicates the time needed at standard conditions to reach a serviceable state.
Special notes for Class C sealants
Assembly Time: The maximum length of time, after mix or thaw of PMF that a sealant remains suitable to assembly parts, including the final torquing of fasteners, to assure proper sealing. The term is used interchangeable with Squeeze-Out Life. The stated Assembly Time will be longer than the sealant Application Time, and is determined at standard temperature and humidity as defined by the procuring specification. Apparent or actual Assembly time will vary with ambient conditions.