390 Silicone Rubber

Code: SYL-1533


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Grade 390 is the stiffest grade of Sylmasta high tear strength moulding rubber for the casting of polyurethane resins

When cured, its stiffness gives it the highest dimensional stability, making it ideal for larger moulds.


Each pack contains catalyst and comes with a free reusable pipette, mixing cup and stirrer.

(For making moulds for Clear Polyurethane Resin please use Grade 400)
Sylmasta Moulding Rubbers are produced to the highest standards for use in industry and model making to produce flexible, highly detailed rubber moulds of all sizes.


The high-quality of Sylmasta silicone rubbers means that once a mould has been taken from the master, it can be used again and again to pour multiple castings using Sylmasta PU Casting Resins.


Sylmasta casting resins have been trusted by professional kit builders and industrial users for years for their high detail and repeatability. Moulds made from Sylmasta Moulding Rubber have low shrinkage with no distortion and good dimensional stability. The long pot life means that there is plenty of time to pour the rubber and allow air bubbles to disperse.


Additional information

Weight 2 kg
Dimensions 18 × 18 × 18 cm

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Key Benefits:

  • Good for larger moulds•
  • High Tear Strength •
  • High elongation •
  • Easy degassing •
  • Chemically resistant

  • Pot Life: 45-120 minutes
  • De-mould: 8 hours
  • Mixed viscosity: 19,500 mPas
  • Shore A hardness: 22° •
  • Elongation at break: 497% •
  • Tensile strength: 3.64 MPa •
  • Tear strength: 26.24 kN/m •
  • Young’s modulus: 1.5 MPa •
  • Linear shrinkage: 0.4% • Min
  • Service temperature: -50°C • Max
  • Service temperature: 200°C
  • Colour when mixed: Pale blue