Mold making liquid silicone is two-part room-temperature curing silicone rubbers that offer great flexibility, tear strength, chemical resistance, and release properties. Well suited for making silicone molds by Pour-on or Brush-On Molds. When making the mold, mix part A and B together and pour into the mold box containing your pattern. After curing, the mold is soft and flexible, and every detail of the pattern can be reproduced.
Features
- Strong and stretchy when cured.
- High tear strength – can be stretched many times its original size without tearing.
- After being stretched, rebounds to its original form without distortion.
- Cures at room temperature (RTV).
- Easy to use, Excellent release properties, Release agent for casting often not necessary.
- High heat resistance (-50~250°C), Can cast low-tempmetal alloys such as tin and pewter.
- Pourable or brushable.
- Very good flowability and self de-airation.
Type of Mold Making Silicone
Mold making silicone usually belongs to RTV silicone rubber (Room Temperature Vulcanizing) . They are available in two general forms, a liquid silicone rubber for molds and a silicone mold putty. Liquid silicone for molds are divided into two families: platinum-cured (also known as addition-cure) silicone and tin-cured (also known as condensation cure) silicone. The chemical catalyst that causes the mold rubber to change from a liquid to a solid contains platinum in the former and tin in the latter, as the names imply.
Tin-Cure Silicone
Tin cured silicones can be poured onto models or they can be made brushable by adding a thixotropic additive. They are ideal for molds where easy release or high temperature resistance is required. Perfect for these mold making applications: Wax, Clay, Polymer Clay, Plaster, Melt and Pour Soap, Precious Metal Clay, Cold and Hot Processed Soap, Casting Resin, Candles, Cold Porcelain, Plastic, Cement, Hot Glue, Low Melt Metals and More!
Of the two, each type of silicone rubber has its own special properties, and both are the preferred. The platinum-cure is the most expensive to purchase due to the precious metal that it contains. But the platinum silicone offers better mold stability, longer life and less shrinkage.
Platinum-Cure Silicone
Platinum cure silicone are two-component high tear strength and flexible mold or casting compounds. They exhibit extremely low shrinkage and high physical properties. These rubbers are chemically sensitive to latex, sulfur, and certain other materials. Also addition-cure silicone is temperature sensitive, so using the platinum-cure silicone in an environment that is too cold may also lead to inhibition.
Platinum-cured silicone is Perfect For These Mold Making Applications: Chocolate, Candy Clay, Marzipan, Sherbet, Sorbet, Butter, Ice Cream, Pulled Sugar, Cheese. Platinum cure silicone can also be used to cast prosthetics for special effects makeup and medical training devices.
Silicone Mold Putty
Silicone Mold Putty is another type of Mold making silicone Material that comes in a 2-part (A+B) form, but each component is in the form of a putty. The A and B putties are combined in equal parts, kneaded together, and shaped by hand around an item to be molded. This type of silicone rubber has a very short open time, typically under three minutes, and you have to work quickly. It usually sets up quickly as well and your mold is typically ready for use within 30 minutes or so.
Making Silicone Molds
After the master pattern is created, a silicone rubber mould can be made. One of the most important characteristics of the silicone rubber is its reproduction accuracy. Silicone rubber is widely known for their extreme degree of detail duplication. The following are two main types of configurations that can be used to create the silicone rubber moulds.
Single stage mould
Single stage mould is one of the most widely practised silicone rubber moulding technique. Under this type of moulding, the master is suspended inside a mould box. Then the liquid silicone rubber is filled inside the box until the box is full. Once the silicone has cured, the mould is cut open in half. This is one of the most cost- and time-effective method to make a silicone mould.
Two-part mould/multi-stage mould
This method is a bit more labour intensive however, this method allows for a better control over the mould parting line along with the capacity to make moulds of bigger parts due to better mould stability. The two-part mould is achieved by making a parting line with a modelling clay. Silicone is then filled to half of the mould in a moulding box. Once the first half of the pour is done, the mould is inverted and the parting line clay is removed with silicone being removed. Then the frame is replaced and the second half of the mould is poured and cured.
Mixing and de-airing
After the type of mould and the silicone rubber is selected, it must be made sure that the two components (catalyst and silicone base) must be weighed accurately in order to meet the design precision. Mixing should also be carried out in a plastic container at least three to four times bigger than the material volume. This allows for the air bubbles to flow out freely during the de-airing process. Any bubbles in the silicone rubber can adversely affect the integrity of the final product.
Advantages
Mold making silicone rubbers are easy-to-use, two-part RTV-curing materials that hold severe undercuts and resist tearing with repeated use. Not only do moldmaking silicone rubbers offer flexibility to reduce de-molding and stress problems, but they also exhibit excellent natural release characteristics and resistance to most chemicals.
Silicone molds are cheaper to produce than metal molds, and they offer high heat resistance, They can be used with masters made of stone, glass, wood, metal, wax, ceramic, plaster and clay in a wide range of service temperatures. They last longer, but they don’t last as long as the steel and other metal molds that can be used.
Silicone molds allows for extreme precision in the reproduction of prototypes for a manufacturer. The process even allows for complex geometries to be factored in and reproduced at a large scale. The results of silicone molds molding are almost identical to the finished product, making it perfect for checking for visuals.
