Silicone

A material with remarkable properties

Silicones occupy an intermediate position between organic and inorganic compounds. They are still relatively young materials, their chemical composition having been discovered only at the beginning of the 20th century. And although industrial-scale production has not been possible until the 1940s, it has since experienced an unprecedented rise in popularity.

The reason for this high demand is that silicones feature a unique spectrum of properties and uses, a versatility unmatched by any other synthetic material. Their exceptional resistance to ageing, weather conditions, radiation, temperature, and chemicals makes them an indispensable material e.g. in the construction or automotive industry. Due to their physiological harmlessness, proper and careful workmanship provided, silicones also play an important part in the manufacture or processing of food and pharmaceutical products, as well as in the field of medical technology.

In the following overview, the most important properties of silicones have been compiled in considerably shortened form.

If you have any further questions regarding this versatile material, its processing, or its potential uses, please get in touch with us! We look forward to personally providing you with all the information you need!

Physiological properties

A large number of our silicone products are physiologically harmless as well as neutral in both odor and taste. That is what makes them specially suitable for use in food-related areas or in conjunction with medical or pharmaceutical products.
Articles deployed in these sensitive fields are thermally treated in our temper furnaces so that they comply with all regulatory requirements: BfR and FDA standards concerning food safety, WRAS, KTW and ACS standards regarding contact with drinking water, as well as all relevant provisions specified in ISO 10993, USP Class VI and E.P. 3.1.9. for medical and pharmaceutical applications.

Ageing, weather, and ozone resistance

Unlike many organic rubbers in need of treatment with anti-ageing additives, silicone rubbers remain unaffected by the influence of ozone. In addition to this exceptional sturdiness, silicones are also resistant to oxygen, UV and high-altitude radiation, as well as to weather conditions of any kind.

Radiation resistance

Exposure to radiation, in terms of the effect it has on silicone rubber, is comparable to the strain imposed on the material by increased temperatures. High levels of exposure lead to gradual embrittlement and reduced elasticity of the rubber. Exposure of up to 10 Mrad has no significant impact on the fracture elongation of standard HTV silicones. Up to a 50% reduction in the original elongation at break, the material is able to absorb radiation doses of approx. 40 - 50 Mrad.

Electric properties

In a temperature range between -60°C and +200°C (-76° F and +392° F), the dielectric properties of silicone remain almost stable. Its excellent insulation properties, which are not only appreciated in the electronics sector, are therefore nearly temperature-independent. In case of a fire, silicone does not form aggressive or corrosive gases, but instead builds an insulating ash from silicone dioxide. If requested, we are able to produce special conductive qualities by way of modifying our mixtures.

Temperature resistance

Silicone is exceptionally resistant both to low and high temperatures. Its physical properties remain highly consistent across a wide temperature range.
Standard types show this resistance in a range between -60° C and +200° C (-76° F and +392° F), special qualities even between -110° C and +300° C (-166° F and +572° F).

Steam resistance

Silicones have an excellent resistance to boiling water as well as to steam of up to approx. 140° C (284° F). Repeated sterilisation is possible, e.g. in medical, pharmaceutical, or food technology applications.
During this process, the hydrophobic character of silicone prevents the absorbtion of water.

Chemical resistance

The resistance of silicone rubber to chemicals depends on its cross-link density and filler content. In heavily swelling media, the use of high-density rubber mixtures is recommended. Silicone, for the most part, reacts neutrally to varnishes and plastics. It also shows a high degree of resistance to aqueous solutions as well as to weak acids and bases, even at higher temperatures. Higher concentrations, however, have to be considered under various aspects and checked for compatibility on a case by case basis. Silicone is also highly resistant to polar fluids (e.g. polyvalent alcohols), whereas its use with non-polar liquids (aliphatic or aromatic petroleum, gasoline etc.) is limited at best: Contact with these substances causes fairly heavy swelling, which is mostly reversible, though, if the exposure has been brief.

Reaction to fire

Standard silicone materials comply with DIN 4102 B2 or UL 94 HB. Appropriate modification of mixtures, however, is able to produce self-extinguishing properties for different requirements. Standard silicone products have a flashpoint (with external ignition) of approx. 400° C (752° F). The firing temperature is approx. 750° C (1382° F), while the self-ignition temperature according to ASTM-D 1929-68 is approx. 430° C (806° F). If silicone catches fire, the composition of the resulting combustion gases depends heavily on temperature and oxygen supply. In case of complete combustion (high temperature, sufficient oxygen), carbon dioxide, water, and silicone dioxide are created. In case of incomplete combustion, in addition to the substances mentioned, carbon monoxide, crack products, and volatile siloxanes can be created as well (siloxanes are considered toxicologically harmless, which is why they are widely used even in the production of cosmetics). Compared to many other sealing materials, silicone products react to fire in a superior way. It should be emphasized that the risk of silicone producing carbon monoxide or other organic molecules is quite low. The production of dioxin can be ruled out completely.

Apart from the generally very positive fire performance of standard silicones, we are able to produce special qualities equipped with self-extinguishing capability. Their fire protection properties depend on the amount of additives, their density, and their material thickness. With the right formula, the requirements of rail and aviation technology can be met as well.

Colors and forms

Silicone products can be manufactured in virtually any lightfast color. Through our own toolkmaking department and the making of our own mixtures, we are also able to provide you with a wide variety of geometric and functional possibilities!