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  • Writer's pictureMarco Bassendowski

Silicone as a material: Less reactive and thus versatile in use

Molds and components made of silicone are an absolute future topic and are used for many different applications. The advantages of the material are obvious: Silicone is flexible, temperature-resistant and chemically inert (lat. for uninvolved, inactive, little reactive). It is also easy to separate and dissolve from most materials. Silicone is therefore suitable for a wide range of applications, especially those involving contact with food.


Applications for silicone molds are:

- Pouring molds for concrete

- Food molds for e.g. chocolate, ice cream, vegan food and sweets

- Soap molds

- Pouring molds for small series production from technical resins

- Medical molds for orthopedic and dental technology

- Resin Art

- and many more (…)


The following sections show some properties that are relevant when selecting the appropriate silicone. We focus here mainly on addition-curing RTV2 silicones (room-temperature-vulcanization), which are most commonly used in manual processing.


Temperature resistance

Many standard silicones can withstand permanent temperatures above 100°C without any problems. If the silicone mold is to be suitable later for applications with higher temperatures, such as in pewter casting, a silicone with high temperature resistance is needed.



Flexibility


A suitable measurement to classify the flexibility of the silicone is the Shore hardness. The various Shore hardness scales are generally used to indicate the surface hardness of plastics. Silicones are usually very soft and therefore often classified in the Shore A range. They cover almost the entire measuring range (Shore A 0-100), with the majority lying between Shore A 20 and Shore A 40.


Hardness examples Shore A:

Jelly babies: Shore A 0-20

Rubber eraser: Shore A 70-85

Car tyres: Shore A 95-100


Food approval

Silikon Lebensmittel FDA BfR Silikonmatte Lebensmittelecht
Molds made of Food Silicone

Not all silicones are approved for contact with skin or food. Here, it is important to ensure that the material has been classified as safe for contact with food. This classification can be done by the FDA (Food and Drug Administration).

The food approval is usually evident in the first lines of the data sheet and the product description.




Processing time


Processing time is an important planning factor. A silicone that cures too quickly can easily start to harden before it could even be poured into the mold. A silicone that cures too slowly can unnecessarily drag out production times.

The technical term that can be found for this in the data sheets of most materials is pot life. However, this should not be confused with the curing or demolding time, which can sometimes be ten times the processing time/pot life.



Viscosity


The viscosity indicates the flowability of the mixed silicone material. It is specified as standard in the unit mPas (milipascal second).

A low viscosity value means that the silicone is rather watery. A high one, on the other hand, describes flow properties comparable to honey.

Low-viscosity RTV2 silicones (approx. 1,500mPas) usually offer lower final hardnesses, while high-viscosity silicones >15,000mPas have higher final hardnesses.



Color

Silikon Form Transluzent lichtdurchlässig Silikonform Formbau Silikonbauteil
Translucent Siliconepart

Sometimes the color of the silicone is helpful in processing. If you are casting filigree models, a translucent silicone mold can be advantageous. When casting the actual model, it makes it possible to see whether all the spaces of the model have been filled.

If bright colors are required, many silicones are available in bright colors. Alternatively, most silicones can be colored as desired using special silicone color pastes.





If you have any questions on the subject of silicones or need help with the realization of your projects, we will of course be happy to assist you.


Simply write to us!


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