Sikaflex 821 FR - Fire Retardant Sealant for Interior of Railway Vehicles

  • Sika Sikaflex 821 FR Joint ignifuge retardateur de flamme pour trains




  • Fire retardant, flame retardant
  • Complies with fire safety standards EN 45545-2 / R22, R23 HL2
  • Solvent and PVC free

Packaging options

  • 600 ml pouch

Description of the Sika Sikaflex 821 FR fire sealant

The Sika Sikaflex 821 FR fire sealant is a single-component, flexible polyurethane fire retardant sealant for professionals.

It is used for interior joints in the railway industry requiring a HL1 or HL2 fire classification according to the European railway standard EN 45545-2.

The Sikaflex 821 FR fire retardant sealant polymerizes under the action of atmospheric moisture. Note: At low temperatures, the amount of water in the air decreases and the curing reaction slows down.

Sika Sikaflex 821 FR Mastic ignifuge conforme à la norme sécurité incendie EN 45545 pour trains et véhicules ferroviaires

Technological Advantages:

  • Good mechanical properties
  • Very good application properties
  • Aging resistant
  • Non-corrosive
  • Adheres well to a wide variety of substrates
  • Excellent hydrolysis stability
  • Low isocyanate content

Chemical resistance properties:

  • Resistant to water, seawater, diluted weak acids and bases.
  • Resistant to temporary action of fuels, mineral oils, vegetable and animal fats.
  • Caution: NOT resistant to organic acids, alcohols, concentrated acid and alkaline solutions, and solvents.

Applications of Sikaflex 821 FR fire sealant

Sikaflex 821 FR fire sealant is developed for interior sealing applications in the railway industry where a fire classification according to EN45545-2 standard is required.

It can be used on a wide variety of substrates and is suitable for making permanent flexible joints.

Compatible materials:

Suitable substrates include metals, metal primers (primers), and paint coatings (two-component systems), ceramics, and plastics.

Preliminary tests on supports under production conditions should always be carried out before final assembly to ensure adhesion and compatibility of materials, especially for surfaces prone to "crazing" (cracking, fissures).

Seek the advice of our technical experts for advice related to your application.

Usage instructions and precautions

  • Sikaflex 821 FR can be applied manually, using pneumatic or electric piston guns.
  • Use with a gun: Place the pouch in the application gun and cut the clip.
  • Sikaflex 821 FR can be applied at temperatures between 10 °C and 35 °C.
  • Changes in reactivity and application properties should be considered.
  • The recommended temperature for the support and adhesive is between 15 °C and 25 °C.

Technical data of Sika 821 FR special train fire sealant

Color Gray, black
Packaging Pouch of 600 ml
Base Single-component polyurethane
Polymerization mode Under the action of moisture
Skinning time 60 min approx.
Shrinkage -2 %
Shore A hardness 45
Application temperature 10 to 35 °C
Fresh density 1,5 kg/L
Tensile strength 2 MPa
Elongation at break 250 %
Tear resistance 9 N/mm
Shear strength 1,8 MPa

Operating temperature

-50 °C à 70 °C continuously
120 °C for 4 hours
100 °C for 24 hours