SILICONES – Definition and Properties
A World of Unlimited Potential
We encounter silicones every day without noticing them. Under the hood, silicone rubber protects car electronics against moisture and dirt; in washing machines, silicone antifoam agents prevent the detergent from foaming over; in shampoo, silicones give hair its sheen; as silicone resin emulsion paints, they give masonry water repellency, while allowing water vapor and carbon dioxide to diffuse out of its interior. But also in medical applications requiring high resistance or cutting-edge products, silicones deliver genuine peak performance – serving as particularly pure material in medical tubing, wound dressings or orthopedic products, and as safe sealing and insulating materials in electrical equipment or insulators.
From Science to Success
The development of the Müller-Rochow process some 75 years ago paved the way for methylchlorosilane to be obtained from silicon metal and methyl chloride. This provided the first-ever access to the starting materials needed for the industrial manufacture of silicones and kick-started the global boom in the use of silicone products in many different applications. WACKER is a pioneer in this field, and was the first company in Europe to begin researching silicones. In the following years, WACKER processes laid the foundations for the modern and efficient manufacturing of organochlorosilanes and silicone products.
This was the beginning of the success story. These early scientific accomplishments underlie WACKER’s reputation as the European pioneer of silicone chemistry. The globally active WACKER Group now develops, produces and markets a versatile product portfolio in a range of complex chemical processes.
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Discover the versatility of Silicones
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Solid silicones remain flexible for their whole life time as no plasticizers are needed.
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A leak-proof, fog-free diving mask ensures the best view. ELASTOSIL® silicone rubber is an important basic product for diving masks. Silicone rubber is highly-transparent, translucent and skin-compatible.
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The mass damper is an important quality determinant in automobiles. ELASTOSIL® solid silicones have a strong damping effect on shocks and undesired vibrations. They also feature good low-temperature flexibility and superior heat and aging resistance.
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Exhaust-pipe suspensions absorb vibrations. Here, ELASTOSIL® silicone rubber is their ideal passenger for material safety and driving comfort. This is due to its outstanding resistance to heat and constant damping properties at both high and low temperatures.
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Silicones withstand a very
wide range of temperatures of
up to 300°C.-
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As a heat-resistant binder for surface coatings, SILRES® silicone resins provide exhaust system surfaces with a functional layer that protects against rapid temperature cycles and extreme heat.
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Textile coatings with ELASTOSIL® silicone rubber are flame resistant, heat-stable, chemical resistant and washable – thus ideal for functional protective clothing such as firefighting jackets.
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ELASTOSIL® silicone rubber ensures that heat and steam from the iron only impact the textiles.
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Silicones stay flexible over a very wide range of temperatures of
down to -50° C; special grades even
down to -100° C .-
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In thermos ELASTOSIL® silicone rubber ensures a secure seal with high temparature resistance. Plus, it is permanently elastic, easy to clean and (more importantly) neutral in terms of odor and taste. Thus, hot and cold drinks keep their full flavor.
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HDK®-based insulation materials are ideal for refrigerators and freezers – where conventional foam insulation simply no longer suffices in light of current insulation thicknesses and stringent legal requirements.
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ELASTOSIL® silicone rubber provides ice-cube trays with extreme low-temperature, enables demolding of the contents and is easy to clean. Plus, it does all of this reliably and lastingly.
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Liquid silicones make sure you simply feel good.
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ADVALON® functional silicone fluids make the teddy fiberfill soft and permanently elastic, with excellent resilience. That enhances the characteristics of stylish teddy bears, making them every child’s snuggly companion.
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Cosmetic tissues belong to the basics in every modern bathroom and are suitable for a variety of personal care applications. Thanks to WACKER silicone emulsions they have noticeable and pleasing tactile effects.
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WETSOFT® silicone fluid emulsions make terry toweling visually appealing and imbue it with enormous absorbency and pleasant softness. SILFOAM® effectively reduces unwanted foaming during washing.
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Liquid silicones offer a smart approach to foam control as performance additive during various (production) processes.
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POWERSOFT® silicone fluid emulsions improve the surface smoothness of fabrics and provide textiles with a very soft, flowing and elastic hand. SILFOAM® effectively reduces unwanted foam during the washing process.
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SILFOAM® effectively reduces unwanted foam during the washing process, in which WACKER fabric care products also help clothes dry faster and leave towels feeling silky smooth.
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In pulp and paper manufacturing, unwanted foaming occurs during numerous production steps. PULPSIL® Pulp Defoamers reduce water and energy consumption, boost pulp quality and reduce bleaching-agent consumption.
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Silicones are exceptional: they enable water-repellency and at the same time allow breathability.
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Professional insulation can significantly improve the energy balance of a building. SILRES® BS silicone emulsions protect the treated insulating materials effectively against damage caused by moisture.
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Silicone oil-in-water emulsions are ideal agents for easy formulation of aqueous care products, such as car polishes. Their silicone active ingredients protect sensitive surfaces like autobody paint finishes, providing gloss and weatherability.
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Insulators must withstand many environmental influences, as these can cause a conductive film to form on the insulator surface, which could impair functionality. A POWERSIL® silicone-rubber coating protects insulators against leakage currents and flashovers.
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The effects and properties of silicones are endless – and so is their potential for further innovation.
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Ventilation masks must fit snugly, but without exerting painful pressure, and must be skin-compatible. SILPURAN® silicone rubber meets all these requirements, being especially soft, transparent and dependable. This supports a successful therapy.
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Wound dressings must provide optimal protection for the wound contact area while being air-permeable and easy to remove. Wound dressings made using SILPURAN® can do that. These hyperpure silicones have high breathability. This promotes healing protects against outside influences.
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Adhesives based on GENIOSIL® XB are characterized by being able to build up strength rapidly and having excellent adhesion even when two different materials are being bonded. They have high temperature stability and no tin catalysts are required.
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Silicones are appreciated for their resistance to UV-light, ozone, radiation, chemicals, microbial and other environmental influences.
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Shower heads are under constant threat from limescale and rust. But that’s not a problem for ELASTOSIL® silicone rubber gaskets and nozzles. Unlike nozzles made from other materials, silicone nozzles are water repellent, hot-water resistant and durable.
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Damp is one of the biggest causes of masonry damage. Preventive measures based on SILRES® BS silicone resins, such as hydrophobization of concrete against ingressing water, chlorides, sulfates and acid rain.
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ELASTOSIL® silicone rubber is used for especially soft and compliant pacifiers and teething rings. Moreover, ELASTOSIL® silicone rubbers are sturdy and easy to clean – and that pleases also mom and dad.
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Remarkably Stable
The backbone of silicones is the Si-O bond, which is much more stable than the C-C bond found in organic compounds. This has far-reaching consequences for the stability and resistance of silicones to a variety of influences. Thus, silicones are notable for their remarkable resistance to thermal and thermo-oxidative stress. They also have reduced sensitivity to electromagnetic or particle radiation (UV, alpha, beta and gamma radiation) compared to organic plastics.
A Versatile Formula
Silicones’ chemical structure allows them to be produced in countless variations. Not only can the functionality of the siloxane units be varied to yield products that possess oily, polymeric, resinous or rubbery properties – the scope for variation can also be further extended by altering the organic groups attached to the silicon. It is this variability which accounts for the impressive diversity found within silicone products: greases, release agents, antifoam agents, paint additives, paper coatings, hydrophobizing agents, high- or room-temperature-vulcanizing silicone rubber grades, and many, many more.
Silanes are the Starting Point
The starting point and chief building blocks for silicone production are silanes. These are produced from silicon and methyl chloride by direct synthesis (Müller-Rochow synthesis). Silanes are low-viscosity, water-white liquids that are soluble in organic solvents. They are also highly volatile due to their low molecular mass.
Structure of Silicones
Silicones, known to chemists as polydimethylsiloxanes, have a structure that resembles quartz modified with organic groups. They consist of an inorganic backbone composed of alternating silicon and oxygen atoms. The two remaining valences on the silicon atoms are occupied by organic groups (chiefly methyls), which are responsible for silicones’ exceptional chemical characteristics.
The Term “Silicone”
The term “silicone” was coined by F. S. Kipping (1863-1949), who recognized the formal similarity between these silicon-oxygen compounds and the equivalent oxygen compounds of carbon (silicones were initially called polysilicoketones). However, the Si-O-Si linkage is better described by the term “siloxane.” Strictly speaking, therefore, the correct term for all silicones is “polysiloxanes.” Nowadays, the term silicone is principally used in connection with the technical applications of polysiloxanes.
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