PR-1826 Class B is a rapid cure, aircraft integral fuel tank sealant. It has a service temperature range from -80°F (-62°C) to 320°F (160°C), with intermittent excursions up to 420°F (216°C).
This material is designed for fillet sealing of fuel tanks and other aircraft fuselage sealing applications. The cured sealant maintains excellent elastomeric properties after prolonged exposure to both jet fuel and aviation gas. PR-1826 Class B is a two-part, epoxy cured Permapol® P-3 polythioether compound.
The uncured material is a low sag, thixotropic paste, suitable for application by extrusion gun or spatula. Unlike standard polysulfide fuel tank sealants, it can cure at low temperatures and is unaffected by changes in relative humidity.
This sealant has excellent adhesion to common aircraft substrates when correctly primed with PR-1826AP Adhesion Promoter
Immediately before applying sealant to primed substrates, the surfaces should be cleaned with solvents. Contaminants such as dirt, grease, and/or processing lubricants must be removed prior to sealant application.
A progressive cleaning procedure should be employed using appropriate solvents and a new lint-free cloth conforming to AMS 3819.
(Reclaimed solvents or tissue paper should not be used.)
Always pour solvent on the cloth to avoid contaminating the solvent supply. Wash one small area at a time. It is important that the surface is dried with a second clean cloth prior to the solvent evaporating to prevent the redeposition of contaminants on the substrate. Substrate composition can vary greatly.
This can affect sealant adhesion. It is recommended that adhesion characteristics to a specific substrate be determined prior to application on production parts or assemblies. After the surface has been cleaned, apply PR-1826AP Adhesion Promoter with a clean brush or a gauze pad. Care must be taken to obtain a uniform thin coat.
At standard temperature, allow the adhesion promoter to dry 30 minutes. It is not recommended to apply adhesion promoter below 45°F (7°C). The sealant must be applied within 8 hours of the application of the adhesion promoter.
If this time is exceeded, the surface should be recleaned and the adhesion promoter reapplied. Do not use adhesion promoter if it contains particles or precipitate.