Tin Cured Silicone Rubber

Tin-cured silicone rubber also known as condensation-cure silicone, consists of two components. Part A is typically a white or translucent pasty gum base, while part B is a clear-to-straw yellow tin curing agent. When these components are mixed at the appropriate weight ratio (usually 2-4%), they cure at room temperature (RTV) to form flexible and highly tear-resistant silicone materials.

During the curing process, a small amount of alcohol is released, which may cause minimal shrinkage (less than 0.3%). Once cured, the silicone becomes elastic, and its brittleness can be adjusted based on the desired hardness level. These silicones are particularly suitable for mold-making applications where easy release and high-temperature resistance are necessary.

Principle of Curing

Tin-cured silicone rubber utilizes tin salts as a catalyst to undergo a transformation from a liquid state to a solid state through the presence of moisture in the air. Unlike other types of silicone, tin-catalyzed silicones are not sensitive to inhibition, which means they can cure at room temperature on almost any surface. These silicones are easy to mix and remove air bubbles from because they have a relatively long curing time, allowing bubbles to naturally rise to the surface. If a faster curing time is desired, it can be achieved by increasing the amount of catalyst used or by incorporating special activators.

The Properties of Tin-Cured Silicone Rubber

  • Excellent release properties: It allows for easy removal from molds or surfaces.
  • Room temperature curing (RTV): It cures at ambient temperature without the need for additional heat.
  • Excellent tear strength: It possesses high resistance to tearing or laceration.
  • High heat resistance: It can withstand temperatures ranging from -50°C to 250°C.
  • Making molds that capture very fine detail: It is suitable for creating molds that can accurately capture intricate details.
  • Excellent chemical resistance: It displays resistance to various chemicals.
  • Pourable or brushable: It can be applied by pouring or brushing onto desired surfaces.

The Applications of Tin-Cured Silicone Rubber

Tin-cured silicone is a preferred material for mold makers and casting artists due to its exceptional flexibility, superior strength, enhanced resistance, and long lifespan. Its versatility allows for its application in almost any situation.

Tin silicone molds are particularly well-suited for casting artificial stone products, commonly used in architectural elements, block-outs, hole formers, concrete countertops, flexible form liners, glass fiber reinforced concrete (GFRC), manufactured stone veneer, ornamental precast items, and statues, as well as stamped and textured concrete.

When using tin-cure silicones, various materials can be cast without the need for a release agent, including wax, gypsum, low-melting alloys/metals, and urethane, epoxy, or polyester resins.

Additionally, tin silicone molds find application in the production of a wide range of precast concrete hardscape products. These include pavers, stepping stones, patio stones, retaining wall blocks, pier, wall caps, and more. Such molds are highly advantageous when the easy release or high-temperature resistance is required.

To learn more about Tin-Cured Silicone Rubber, contact A1 Silicones

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