Tin cured silicone rubber is also called condensation-cure silicone, It consist two components (part A usually white or translucent pasty gum base and part B clear to straw yellow tin curing agent), which, after mixing at the proper ratio by weight (usually 2~4%), cure at room temperature (RTV) to flexible, high tear-strength silicons. During cure a small amount of an alcohol is evolved. This can cause a slight amount of shrinkage (less than 0.3%) . After curing, the silicone is elastic. Its brittleness depends on the chosen degree of hardness. They are ideal for molds where easy release or high temperature resistance is required.
Principle of Curing
Tin (condensation) cured silicone rubber uses tin salts as a catalyst and uses moisture in the air to transform from liquid to solid. Tin catalyst silicones are not sensitive to inhibition, meaning they will cure at room temperature over virtually any surface. They’re easy to mix and de-air, because they have a relatively long curing time which allows bubbles to rise to the surface. The cure time can be reduced either by increasing the amount of catalyst used, or by adding special activators.
- Excellent release properties
- Room temperature curing (RTV)
- Excellent tear strength – High resistance to laceration
- High heat resistance (-50~250°C)
- Making molds that capture very fine detail
- Excellent chemical resistance
- Pourable or brushable
- Excellent chemical resistance
Tin-cure silicones is a material of choice for many mold makers and casting artists. The excellent flexibility, superior strength, enhanced resistance and long life work in its favor apart from the versatile usage for almost any application.
Tin silicone molds are great for Artificial Stone casting products, which is widely used for architectural elements, block-outs & hole former, concrete countertops, flexible form liners, GFRC, manufactured stone veneer, ornamental precast & statuary, stamped & textured concrete etc.
Tin-cure silicones can used to cast a variety of materials including wax, gypsum, low melt alloys/metals and urethane, epoxy or polyester resins (without using a release agent).
Tin silicone molds are also used to produce various precast concrete hardscape products, including pavers, stepping stones, patio stones, retaining wall block, pier and wall caps and more. They are ideal for molds where easy release or high temperature resistance is required.
How to Use
Step 1: Prepare the Original Molds
Make your original molds perfect. fix it on a board. And fix the original mold on a board , then used four piece of board to enclose the original molds.
Step 2: Applying A Release Agent
Although not usually necessary, a release agent will make demolding easier when pouring into or over most surfaces.
Step 3: Weighing
Determine the volume of silicone needed to fill your mold, Measure desired amount of silicone and hardener separately in two measuring cups.
Weigh the two-part exactly by electronic weight. If not, for example, add too much catalyst, the operation time will be too fast to operate, which will cause inconvenience to operate.
Mixtures are determined by weight, not volume.
Step 4: Mixing
Mix part A and part B evenly. Otherwise, the silicon rubber will be partly solidified and this will give birth to difficulties in your final operation.
Step 5: Vacuum pumping(optional)
Recommends degassing the mixed product before casting to remove air from hand mixing. The vacuum must be capable of pulling 29” of mercury and the silicone must be in a container large enough to accommodate the rising air. These products can rise to over 4 times their initial volume.
Step 6: Pouring casting or Brush operation
Pour in a thin unbroken stream into the lowest point in the cavity or mold. This will help break up some of the air entrapped during mixing.
For simple pattern products, we suggest using pouring operation way, which will be very easy to operate and demould. Pourable silicone requires low viscosity which will be easy to flow smoothly and easy to de-air.
For delicate pattern products, we suggest using brushing operation way, which can copy the pattern exactly. Brushable silicone requires high viscosity which won’t be easy to flow away and easy to brush.
Atmospheric temperature and humidity vary from season to season. In winter months the pot life and curing time will be nearly twice their summer values. Demould will be 8-12hrs depending on ambient temperature and humidity.
We suggest setting the silicone mould for another 12 hours after demould before you put it into a large production.
- Because no two applications are quite the same, a small test application to determine suitability for your project is recommended if performance of this material is in question.
- This material has a by-weight mix ratio. An accurate gram scale is recommended.
- Vacuum degassing mixed material using a vacuum pump and chamber to remove entrapped air is recommended.
- Tin silicone curing needs need air and moisture to cure, not good for confined spaces.
- Do not cure rubber where temperature is less than 15°C, Because it will be hard to cure.
- Use the silicone and hardener that came together in the same kit. Using one brand’s hardener with another brand’s silicone may keep the mixture from curing.
- No release agent is necessary when casting wax or gypsum. Applying a release agent prior to casting polyurethane, polyester and epoxy resins is recommended to prevent sticking and mold degradation.
- The physical life of the silicone mold depends on how you use it (materials cast, frequency, etc.). Casting abrasive materials such as concrete can quickly erode mold detail, while casting non-abrasive materials (wax) will not affect mold detail.
Shelf life is 12 months from the date of production. Store material at room temperature (73°F/23°C). Storing material at warmer temperatures will also reduce the usable shelf life of unused material. Storage beyond the date specified on the Certificate of Analysis does not necessarily mean that the product is no longer usable. In this case however, the properties required for the intended use must be checked for quality assurance reasons.
- Use in a properly ventilated area (“room size” ventilation). Wear safety glasses, long sleeves and rubber gloves to minimize contamination risk. Avoid splashing into eyes. If it occurs, rinse with plenty of water immediately and consult a doctor.
- Adult Supervision Required. Keep Out of the Reach of Children.