Silicone Mold Rubbers

silicone-mold-rubbersThese two-part (Part A & Part B), room temperature curing rubbers offer great flexibility, tear strength, chemical resistance, and release properties. Silicone molds can be used to cast a variety of materials.

Typical Casting Materials


If cast resin parts need to be painted, silicone mold rubbers are often preferred as release agent is not necessary. Release agent, which is needed when casting resin in polyurethane rubber molds, must be washed off prior to painting and can be difficult to remove.

Silicone mold rubbers are more expensive than polyurethane rubbers, but well worth the expense when high-volume resin casting is required.


Platinum-cured and tin-cured systems are available:

Rubber Type Advantages Disadvantages Casting Materials Methods
Platinum-Cured Silicone Mold Rubbers No shrink on cure, cured rubber has long storage life, high strength, excellent chemical resistance. Liquid rubber can suffer from cure inhibition by some materials (e.g., sulfur clay, tin silicones, Bondo, some 3D-printed plastics, latex rubber). Most materials, especially resins, foams and some low-melt metals. Pour, Brush, Spray.
Tin-Cured Silicone Mold Rubbers High strength, excellent chemical resistance, slightly less expensive than platinum-cured systems. Shrinks on cure (~1%), shorter library life (2-5 yrs.) than platinum-cured systems. Most materials, especially resins, foams and some low-melt metals. Can inhibit polyurethane rubber, platinum-cured silicone, and 14-Series Poly-Optic Resin castings. Pour, Brush, Spray.
For assistance in selecting a mold material – Call: 800.858.5990 | Email: sales@polytek.com | Online Contact Form