Silicone compound for the manufacture of molds: technical specifications

Silicone compound is an ideal material for making molds of fossils, lifecastings and other hard objects. As a liquid latex, it gives a light, flexible, high-precision shape. Also has additional advantages - longer service life and chemical resistance and decomposition. This is the recommended material for the manufacture of durable forms from important samples. Silicone molds for gypsum can be made in less time than the latex mold, if "fast" catalysts are used. The only drawback is that it is more expensive than latex, and not so elastic, which leads to tears and damage.

Composition of silicone material

This material consists of a silicone paste as a base and a platinum catalyst that accelerates hardening.

When creating forms, use a compound of silicone transparent, red, yellow, white and other colors. The curing agent can also have a different palette or be colorless.

After mixing the two components at room temperature, the silicone mass becomes solid and acquires a rubber-like appearance. The usual hardening time for most is between 18-24 hours, but the pour point can be significantly reduced by using high-speed catalysts.

Types of silicone compounds

The most common rubber compounds used to produce molds are RTV, RTV-2 and HTV. Unlike rubbers RTV (vulcanizing at room temperature) HTV silicone requires for curing temperature conditions exceeding 100 ° C.

Among those who manufacture silicone compound, everyone tries to make a lot of silicones and catalysts with different viscosity, color and other functions.

There are two main classes of RTV-silicones

1. Tin catalyzed silicones.

2. Silicones on platinum catalysts.

Each of them has advantages and disadvantages. Tin-catalyzed silicones are generally cheaper and easier to use. They have a low to medium viscosity, so they flow well around the product. In contrast, platinum is suppressed by many naturally occurring compounds, in particular sulfur, tin, amines, newly manufactured polyester, epoxy or urethane rubber products. Even after coating the product with acrylic lacquer, the silicone compound for molds on platinum will not solidify in the presence of interaction with sulfur- and tin-containing surfaces. This makes them unsuitable for many natural objects. Nevertheless, after curing, they have the greatest chemical, microbiological and heat resistance ability and generally remain flexible for many years. In contrast to tin, the catalyzed silicones tend to become brittle after several years of use and begin to split or tear. For these reasons, silicones in the tin group are often used for low-volume casting jobs. And platinum is used for important work, especially in large volumes.

Terms of storage

Many silicones can be successfully used up to 5 years from the date of purchase if they are stored properly in sealed containers in a dry, cool place. Nevertheless, catalysts lose their effectiveness quite quickly, even with proper storage, they are best used for a year.

Where to apply

Silicone compound RTV-2 is used to make copies of a variety of figurines. And also art products from polyester, epoxy resins, wax, gypsum, candles, toys and soap, etc.

Silicone compound "Pentelast" is food and safe. The advantage of this material is that it is highly flexible and does not damage the product when removed, such rubber molds can be used repeatedly. Considering that this food silicone is on a platinum catalyst, it can be used to make silicone molds for gypsum, forms for cakes and cakes, pastries and other confectionery products.

Safety Notice

Silicone compound is a relatively safe odorless product when used correctly, but catalysts and thickeners can be toxic to the eyes and skin, so these parts of the body must be protected.

Procedure for creating forms

• The surface of the copied sample is cleaned and degreased. If necessary, wax grease, soap solution or petrolatum is used.

• The material is thoroughly mixed, as a deposit can form during storage.

• Prepare a container in which the base for the impression is placed. Such a container may be a plastic cup, a bottle or a box. It should have a relatively straight bottom and sides without cracks and holes.

• In a clean container, dilute the base with hardener until a uniform mass is formed.

• In order to estimate the amount of silicone required, it is necessary to calculate the poured volume in such a way that the product is completely covered. Another option - you can simply cover the surface of the product with holes and depressions, after hardening pour another portion of silicone, in this case, save silicone and money. In order to evenly coat the sample, it is desirable to pour or apply the silicone in two or more batches. The second batch is applied over the cured first, but still sticky. It is also possible to use gauze or other reinforcing materials to be embedded between the layers, which makes it possible to produce a stronger shape.

• The catalysts are mixed in proportions depending on the type of silicone. Some of them use a base to catalyst ratio of 50:50. Mixing can be done mechanically or manually with a spoon or a stick. Do not get carried away by this process for more than 2 minutes, since a long process forms many air bubbles in the mixture. In order to know if a uniform consistency has formed, it is better to take a color hardener.

• After mixing, the mass pours out as quickly as possible. The material cures to a rubbery state for 24 hours. At temperatures below +23 ° C, the setting time will be longer.

What you need to consider

Air bubbles can be brought to naught by first mixing a small part of the mixtures and using a brush to cover the sample with it. Thus, not only the annihilation of bubbles is achieved, but also the clarity of the outline of the shape. After applying a thin layer, leave the product at rest at room temperature until the mixture is freed from air and freezes. Then, the remaining portions of the hardener are mixed with the substrate and applied to the products to form the finished product. In the laboratory, this process is simpler, as it is done with machines that shake the mold and release air. In clandestine conditions, you can shake yourself by tapping on the surface.

If the sample does not have natural boundaries, to prevent spreading of silicone during pouring, it will be necessary to build a retaining wall around the sample. This can be done with any inert material, such as wood boards, boards, cardboard, etc. Lock and seal the walls with adhesive tape, so that the silicone does not leak through the cracks.

Attention! Certain types of silicone can slightly discolor some types of rocks from which the mold is made. Before work, it is suggested to check and conduct an experiment with an insignificant sample before using them on valuable items.