PRC-Desoto PR-1440 Class B Fuel Tank Sealant - MIL-S-8802F Type II
Sealing the fuel tank is probably not your favorite thing to do with the aircraft, or even your second favorite. You want to do it right so you only do it once, and that means the most reputable products with the most reliable results.
Thankfully, if you're reading this, you'll be happy to know DeSoto is the sealant expert. They start with a proven, expert formula; they listen to their customers, and they build on that formula, adjusting it until they have a line of products that offer exactly what is needed for specialized uses.
Have you tried DeSoto PR-1440 Class A on fuel tank fasteners? If you have then you can take comfort in knowing DeSoto PR-1440 Class B, has all the same strengths – such as the low service temperature of -65 degrees Fahrenheit, and the durability against constant assault by jet fuels and aviation gas.
PR-1440 Class B Fuel Tank Sealant is made for fillet sealing inside the tank rather than for brushing. The thick paste can be applied by spatula, extrusion gun, putty knife, or other like tools. You can buy it premeasured and mixed or buy it in two-part cans and mix it yourself. Whatever your preference, it's here.
Read the Technical Data Sheet.
PRC and Pro-Seal Aeroscape Sealants Application Guide
PRC-DeSoto International PRC®, Pro-Seal®, Permapol® P-3 brand products are designed for interior/exterior aircraft sealing and coating applications. The traditional Polysulfide and the high performance Polythioether compounds are used for fuel tank sealing, corrosion inhibition, aerosmoothing, electrical insulation, windshield/canopy sealing, priming and topcoating.
Note: It is important to read and understand the MSDS, process specification, and technical data sheet before working with these products.
Immediately before applying sealant to primed substrates, the surfaces should be cleaned with a solvent i.e., Desoclean® 110. Contaminants such as dirt, grease, and/or processing lubricants must be removed to insure good adhesion prior to sealant application.
A progressive cleaning procedure should be employed using the appropriate solvents and new lint free cloth (reclaimed solvents or tissue paper cannot 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 of sealant on production parts or assemblies.
Special notes: For integral fuel tank repair where fresh sealant will be applied over aged fuel soaked sealant, the use of an adhesion promoter like PR-148 or PR-182 is essential.
If a Polythioether is to be applied over a polysulfide, either PR-186 or PR-1826 AP must be used at the sealant interface.
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.
PRC-DeSoto International Sealants are generally available in three different package configurations:
Proper mixing and correct component proportions are extremely important to assure optimal results.
Two-part can kits
Note: Slow mixing by hand is recommended. A high speed mechanical mixer should not be used as internal heat will be generated reducing application life and introducing air in mixture.
Injection style Semkit® package
Note: Use even pressure; do not use force, tap, pound, or jolt ramrod if piston does not break loose readily.
Note: It may be desired to use a Semco® mixer model 388 for mixing sealants packaged in cartridges. Mixer does not reduce the number of strokes required for complete mixing, it does allow the material to be mixed easier and faster.
Two-part kits and Semkit® package
Sealants should be stored according to the instructions on the container.
Premixed and frozen (PMF)
Polysulfide sealants in a PMF form should be stored in a freezer at –40°F (-40°C) or below for optimal retention of application properties and shelf life.
Polythioether sealants require extreme low temperature refrigeration at –80°F (-62°C), or below for optimal retention of application properties and shelf life.
Thawing of PMF can be accomplished in two ways:
Ambient Thaw: Place the PMF cartridge to be used on a bench in a vertical position. Let stand at 70-80°F (21-27°C) for approximately 30 minutes. Dry any condensation from the exterior of the cartridge prior to use.
Water Bath Thaw: Place the PMF cartridge upright in a 120°F (49°C) water bath for approximately 4-6 minutes. Upon removal from the bath, carefully dry the exterior of the cartridge before using.
Application life and cure times are dependent upon ambient environmental conditions. Increases in temperature will shorten application and cure time. Conversely, lower temperatures will increase application life and cure time.
Manganese dioxide cured polysulfides: relative humidity affects the cure rate. Low humidity increases tack free and cure times. High humidity accelerates or shortens the cure time for manganese dioxide cured polysulfides.
Cure may be hastened by applying heat. Polysulfide sealants with a two hour, or less, application time, can obtain a serviceable cure hardness of 30 Durometer A after eight hours at 125±5°F (52±3°C).
Although polysulfide sealants develop a high state of cure in 14 days at 75°F (25°C), longer cure times further improve ultimate resistance to fluids, heat, and pressure. Maximum cure is usually obtained in 30 to 50 days.
Cleaning of application equipment
Wash equipment with a non-chlorinated solvent immediately after use or before sealant cures. Use commercial stripping compounds to remove cured sealant.
Health and safety
Before using a 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. Avoid overexposure. Obtain medical care in case of extreme overexposure.