P/S 890 Class B is an aircraft integral fuel tank sealant. It has a service temperature range from -65°F (-54°C) to 250°F (121°C), with intermittent excursions up to 275°F (135°C). This material is designed for brush and fay 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.
P/S 890 Class B is a two-part, manganese dioxide cured polysulfide compound. The uncured material is suitable for application by brush in thickness up to 25 mils. It cures at room temperature to form a resilient sealant having excellent adhesion to common aircraft substrates.
The following tests are in accordance with MIL-S-8802 Class A specification test methods.
Application properties (typical)
Color Part A: Black
Color Part B: White
Color Mixed: Gray
Mixing ratio By weight: Part A:Part B, 10:100
Base viscosity (Brookfield #6 @ 10 rpm), Poise (Pa-s): 250 (25)
Application life and cure time @ 77°F (25°C), 50% RH
Performance properties (typical)
Cured 14 days @ 77°F (25°C), 50% RH
Cured specific gravity: 1.55
Nonvolatile content, %: 85
Ultimate cure hardness, Durometer A: 50
Soluble chromate, %: 4
Peel strength, pli (N/25 mm), 100% cohesion JP-4 fluid immersion, 7 days @ 140°F (60°C)
MIL-A-8625 (Anodized aluminum): 38 (169)
MIL-C-5541 (Alodine aluminum): 39 (173)
MIL-C-27725 (IFT coating): 38 (169)
MIL-S-5059 (Stainless steel)*: 40 (178)
MIL-T-9046 (Titanium comp. C)*: 34 (151)
QQ-A-250/13 (Alclad): 34 (151)
JRF/NaCl-H2O immersion, 7 days @ 140°F (60°C)
MIL-A-8625 (Anodized aluminum): 37 (165)
MIL-C-5541 (Alodine aluminum): 38 (169)
MIL-C-27725 (IFT coating): 39 (173)
MIL-S-5059 (Stainless steel)*: 38 (169)
MIL-T-9046 (Titanium comp. C)*: 35 (156)
QQ-A-250/13 (Alclad): 39 (173)
*Primed with PR-148 Adhesion Promoter
Tensile strength, psi (KPa) Standard cure, 14 days @ 77°F (25°C), 50% RH: 350 (2413)
Elongation, % Standard cure, 14 days @ 77°F (25°C), 50% RH: 250
Thermal rupture resistance - Retains pressure of 10 psi with only negligible deformation, both before and after immersion in JRF.
Low temperature flexibility @ -65°F (-54°C) - No cracking, checking or loss of adhesion.
Corrosion resistance - No corrosion, adhesion loss, softening, or blistering after 20-day immersion in 2-layer salt water/JRF @ 140°F (60°C).
Resistance to hydrocarbons - 7 days @ 140°F (60°C) immersed in Type III fuel.
Weight loss, %: 4.0
Flexibility - No cracks after bending 180 degrees over 0.125 inch (3.18 mm) mandrel.
Repairability to itself - Excellent to both freshly cured as well as fuel aged and abraded fillets.
Resistance to other fluids - Excellent resistance to water, alcohols, petroleum-base and synthetic lubricating oils, and petroleum-base hydraulic fluids.
Fungus resistance: Non-nutrient
The application and performance property values above are typical for the material, but not intended for use in specifications or for acceptance inspection criteria because of variations in testing methods, conditions and configurations.
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.
For a more thorough discussion of proper surface preparation, please consult the SAE Aerospace Information Report AIR 4069. This document is available through SAE, 400 Commonwealth Avenue Warrendale, PA 15096-0001.
P/S 890 Class B is supplied in a two-part kit. Mix according to the ratios indicated in the application properties section. Mix Part A and Part B separately to uniformity, then thoroughly mix entire contents of both parts of the kit together taking care to avoid leaving unmixed areas around the sides or bottom of the mixing container.