Fuel, Oil, Solvent and Chemically Resistant Fluoro Liquid Silicone Rubber (F-LSR) - Silastic® FL 40-9201

Silastic® FL 40-9201 F-LSR is a two-component, pigmentable fluorosilicone soft paste. It is specially engineered for liquid injection molding. On heating, it is cured to a 40 durometer material. The cured rubber material shows resistance to a myriad of chemicals and solvents over a temperature range of -63°C to +175°C in immersion conditions, and up to +225°C under dry heat conditions.

Applications of Silastic® FL 40-9201 F-LSR

Silastic® FL 40-9201 F-LSR is neither validated nor represented as suitable for pharmaceutical and medical purposes. The following are the applications of Silastic® FL 40-9201 F-LSR:

  • Chemical environments and industrial applications
  • Complex components with close tolerances
  • Solvent and chemically resistant molded components
  • Electrical/electronic connectors
  • Extrusion onto wires, belts, fabrics, and other surfaces
  • Thin, high-precision coatings

Typical Properties of Silastic® FL 40-9201 F-LSR

The typical properties of Silastic® FL 40-9201 F-LSR are listed in the following table:






Color Part A Straw Yellow
Color Part B Translucent
0364 Extrusion Rate g/min 10-40
As Molded3
D792 Specific gravity 1.438
D2240 Hardness Shore A 35-45
D412 Die C Tensile strength MPa
8.3 min
1200 min
D412 Die C Elongation at break % 300 min
D642 Die B Tear strength kN/m
17.5 min
100 min
D263 Bashore resilience % 12-22
D385 Method B Compression set after 22 hours at 177°C (351°F) % 30max
D471 Fluid resistance - Volume swell %
Dexron III, 24 hours at 150°C % 1.0
5W30 Motor Oil, 24 hours at 150°C % 1.5
IRM 903, 24 hours at 23°C % 3.0
Reference Fuel C, 24 hours at 23°C % 20.3
Reference Fuel B, 24 hours at 23°C % 17.0

1Materials were tested according to Dow Corning Corporate Test Methods, which in most cases are similar to the ASTM standard listed above. Copies of CTMs are available on request.
2ASTM: American Society for Testing and Materials.
3Cure conditions: molded 10 minutes at 177°C (350°F); post-cured 4 hours at 200°C (392°F).

Key Features of Silastic® FL 40-9201 F-LSR

The following are the key features of Silastic® FL 40-9201 F-LSR:

  • Two-component product with convenient 1:1 mix ratio
  • Rapid cure at elevated temperatures
  • Free from solvents (100 percent solids)
  • Stable over a broad temperature range
  • Good tensile and tear strengths for better performance
  • High temperature mold release
  • Superior resistance to fuel, oils, solvents and chemicals

Mixing and De-airing of Silastic® FL 40-9201 F-LSR

The two-component Silastic® FL 40-9201 F-LSR is offered as parts A and B, of which Part A is straw yellow and Part B is translucent to facilitate identification and monitoring of the mix. These parts need to be mixed in a 1:1 ratio. Silastic® FL 40-9201 F-LSR can be applied by:

  • Injection molding equipment
  • Extrusion coating onto a substrate
  • Hand brushing onto a surface

For production, it is recommended to use meter mix equipment to pump, meter and mix the two parts without introducing air. De-gassing the mixture needs to be done under vacuum to avoid the entrapment of air bubbles.

Pot Life of Silastic® FL 40-9201 F-LSR

After mixing the two parts, the usable life of Silastic® FL 40-9201 F-LSR will extend for at least 96h at room temperature. The usable life after mixing can be extended considerably by refrigerating at low temperatures. The usable life of Silastic® FL 40-9201 F-LSR is 12 months from the date of manufacture when stored in the original unopened containers at or below 32°C. This product is offered in lot matched pail (22kg and 22kg) and drum kits (205kg and 205kg).

Cure Rate

Heating Silastic® FL 40-9201 F-LSR to 150°C cures it within seconds. The cure time for a specific component is the time required to bring the part to this temperature. The cure time for Silastic® FL 40-9201 F-LSR is a function of cure temperature and the dimensions of the component being cured. The cure cycle ranges between 20 and 90s for injection molding of parts under 10g at a cure temperature of 200°C. Determining curve level by running a MDR curve at the desired molding temperature yields optimum results.

Cure Inhibition and Clean-Up/Removal

The avoidance of contamination is important as the presence of tin complexes, sulfur, amines and some peroxides can inhibit the cure mechanism of t Silastic® FL 40-9201 F-LSR. The uncured product can be cleaned up using solvents like Dow Corning® OS Fluids, xyline, toluene, naphtha, and mineral spirits. Cleaning can also be done with IPA, but it is less effective.

This information has been sourced, reviewed and adapted from materials provided by Dow Corning Automotive.

For more information on this source, please visit Dow Corning Automotive.

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