What Is Silicone? Types, Production and Uses

Silicone (polysiloxane) is a family of synthetic polymers whose main chain consists of silicon–oxygen bonds rather than carbon. This structure provides a combination of properties that organic polymers cannot match: flexibility over an extremely wide temperature range, UV and ozone resistance, water repellency and chemical stability.

What is silicone?

The backbone that defines silicone is the –Si–O–Si–O– sequence. The organic groups attached to the silicon atoms (mostly methyl) determine the character of the polymer. The Si–O bond is stronger than the C–C bond and offers high chain rotational freedom; together, these two properties explain why silicone remains flexible even at −50°C while still functioning without degradation above 200°C.

Note: in Turkish, "silikon" (polysiloxane), "silisyum" (the element, Si) and "silika" (silicon dioxide, sand/quartz) are frequently confused. These are three distinct substances, although the starting point of the chain is silicon in every case.

How is it produced?

The chain starts from quartz and proceeds in four steps:

1. Metallurgical-grade silicon: quartz is reduced with carbon in an electric arc furnace.
2. Direct process (Müller–Rochow): silicon powder is reacted with methyl chloride in the presence of a copper catalyst, yielding a mixture of chlorosilanes, primarily dimethyldichlorosilane.
3. Distillation: the chlorosilanes are separated with great precision — the quality of the silicone is determined at this stage.
4. Hydrolysis and polymerization: the chlorosilane reacts with water, and the resulting siloxanes are built up to the desired molecular weight through ring-opening or condensation reactions.

Depending on molecular weight and degree of cross-linking, the final product takes the form of an oil, emulsion, gel, elastomer or resin.

Types and varieties

Which industries use it?

• Construction and building chemicals: glass facade sealing, joint sealant, facade water repellent. Silicone's resistance to UV and weathering is decisive here.
• Cosmetics: film former in hair care, skin slip and feel; volatile siloxanes serve as carriers in makeup products.
• Healthcare: medical tubing, implants, wound dressings — biocompatibility and resistance to sterilization.
• Automotive and electrical: high-temperature gaskets, cable insulation, thermally conductive paste.
• Textiles: softening finishes and water-repellent finishing.
• Paints and adhesives: defoamers, slip agents, silane-based adhesion promoters.

The Turkish market and production

Because the upstream stage of the silicone value chain (metallurgical-grade silicon and chlorosilane production) requires high energy input and scale, it is concentrated among a limited number of producers worldwide; Türkiye is an importer at this stage. Domestic activity is concentrated mainly on formulation and filling: construction mastics, textile finishing agents, cosmetics and mold release products are manufactured by local companies.

Current industry topics include: siloxane regulation (particularly the impact of restrictions on cyclic D4/D5/D6 siloxanes on cosmetics and personal care formulations), silicon metal prices and energy costs, and mastic demand linked to facade and insulation investments. You can follow the latest developments in the news items below.

Technical properties

Silicone's mechanical strength is lower than that of organic rubbers; it may not be sufficient on its own in applications requiring tear and abrasion resistance. However, it retains these properties with virtually no change over time and temperature — a silicone gasket remains close to its original flexibility even after ten years, whereas an organic rubber may harden and crack over the same period.

Points to consider in selection and procurement

• Ask about the cure type. Acetoxy (vinegar-smelling) systems can attack metal and marble; neutral (oxime/alkoxy) systems are preferred on these surfaces.
• Specify in the design that it cannot be painted over. A joint sealed with silicone cannot subsequently be painted; the sequence of work must be planned in advance.
• Prevent contamination in the production area. In a facility with a paint line, silicone-containing products should be kept in a separate area — this is usually the source of cratering problems.
• Request the application certificate. In facade and medical applications, compliance of the product with relevant standards must be documented.
• Monitor siloxane regulation. Restrictions on certain cyclic siloxanes in cosmetics and personal care formulations remain ongoing.

Frequently asked questions

What is the difference between silicone, silicon and silica?

Silicon is the element on the periodic table (Si). Silica is silicon dioxide (SiO₂) — the main component of sand and quartz. Silicone is a synthetic polymer with an Si–O backbone. The production chain starts from silicon, but the three substances cannot be used interchangeably.

How do you choose between silicone sealant and polyurethane sealant?

Silicone is superior in UV, weathering and temperature resistance, and adheres very well to non-porous surfaces such as glass and ceramic — but it cannot be painted over. Polyurethane sealant can be painted and has high mechanical strength, but degrades gradually under UV exposure. Silicone is preferred for facade glazing, while polyurethane or MS polymer is preferred for joints that will be painted.

What is silicone's actual temperature resistance?

Typical elastomer systems operate continuously between −50°C and +200°C; special formulations can reach up to 300°C for short periods. While most organic rubbers harden and crack at the upper end of this range, silicone retains its flexibility.

Why doesn't silicone adhere well to sticky surfaces?

Low surface energy is a fundamental property of silicone, which is why it is used as a mold release agent and water repellent. The same property means that paint or adhesive cannot be applied to a surface contaminated with silicone — keeping silicone-containing products in a separate area in facilities with a paint line is standard practice.

Can silicone be recycled?

Because cured silicone elastomer is a thermoset, it cannot be melted down and reshaped. Work is underway on grinding it for use as filler or on chemical depolymerization back into siloxane monomers, but large-scale commercial application remains limited so far.