What is silicone rubber—and what makes it so special?
Silicone rubber is a synthetic elastomer composed of silicon, oxygen, carbon, and hydrogen. Unlike organic rubbers (e.g., EPDM, nitrile rubber, or natural rubber), whose backbone consists of carbon-carbon bonds, silicone rubber is based on a silicon-oxygen chain—the so-called siloxane backbone. This inorganic basic structure gives it properties that no other elastomer offers in this combination:
- Extreme temperature resistance from –60 °C to +250 °C (special grades up to +300 °C), without any significant change in mechanical properties
- Chemical inertness toward most media, UV radiation, ozone, and aging
- Excellent electrical insulation over a wide range of temperatures and frequencies
- Biocompatibility, which makes it suitable for direct contact with food, skin, and body tissue
- Low compression set — Seals retain their resilience for decades
This combination of properties makes silicone rubber simply irreplaceable in many critical applications. Where other materials force a compromise between temperature resistance and flexibility, or between chemical resistance and biocompatibility, silicone delivers both at the same time.
An Overview of the Most Important Types of Silicone Rubber
Not all silicone rubber is the same. This material class encompasses a wide variety of types that differ fundamentally in terms of processing methods, cross-linking mechanisms, and performance profiles. To select the right material for your application, you need to understand these differences.
High-temperature vulcanizing silicone rubber (HTV / HCR)
HTV silicone—also known in technical terms as high-consistency rubber (HCR)—is a firm, high-viscosity rubber that is vulcanized under heat and pressure. It is the classic “workhorse” of the silicone industry and has been used for decades in molded parts, extruded profiles, and sheets.
It is typically processed using compression molding, transfer molding, or extrusion. HTV offers excellent mechanical strength and can be tailored to a wide range of Shore hardness levels (20 to 80 Shore A) through specific formulation.
Typical applications: Seals and O-rings for high temperatures, cable insulation, exhaust hangers in the automotive industry, high-voltage insulators, fire-resistant coatings, and profiles for the construction industry.
Recent Development — Ceramicizing HTV Compounds: A particularly exciting innovation in the EV sector: When exposed to fire, these special formulations form a ceramic protective layer that maintains dielectric protection even in the event of thermal runaway in a battery cell. They are increasingly being specified for coating busbars and coolant lines in high-voltage battery packs.
Liquid silicone rubber (LSR)
Liquid Silicone Rubber (LSR) is a two-component, plate-cured system with low viscosity that is processed using liquid injection molding (LIM). The addition-curing reaction is odorless and produces no volatile byproducts—a key advantage for medical and food-contact applications.
LSR has become the fastest-growing segment in the silicone rubber market. The reasons: high automatability, excellent reproducibility over millions of cycles, and the ability to produce the most intricate geometries with tight tolerances.
Typical applications: Seals for electronics and sensors, automotive connectors, disposable medical products (catheters, respirator mask valves, insulin pump components), baby and kitchen products, keypads, and membranes.
Why the medical market dominates the LSR sector: Medical-grade materials account for approximately 44% of global LSR sales. The reason lies in regulatory requirements: ISO 10993, USP Class VI, and the EU Medical Device Regulation (MDR) demand the highest raw material purity, extensive biological safety testing, and complete batch traceability. These requirements favor LSR over other elastomers because the platinum-cured addition system represents the purest of all silicone cross-linking methods.
Room-temperature-curing silicone rubber (RTV)
RTV silicones constitute the broadest and most versatile product family. They cure at room temperature and require no special processing equipment—making them the material of choice for sealing, bonding, potting, and coating applications.
RTV-1 (one-component): Cures by reacting with atmospheric moisture, working from the surface inward. Ready for use immediately; ideal for joints, surface seals, and bonding applications in the field. Typical curing rate: 2–3 mm depth per 24 hours.
RTV-2 (two-component): Both components are mixed before application. This allows for significantly greater layer thicknesses, controlled cure times, and a wider range of formulations. RTV-2 is the basis for mold-making silicones, potting compounds for electronics, and—increasingly important—foamed-in-place gasket (FIPG) systems in the automotive sector.
Typical applications: Joint and construction joint sealing, structural glazing, electronics encapsulation and potting, mold making for prototyping and arts and crafts, bonding and sealing applications in equipment manufacturing, battery pack sealing in electric vehicles.
Fluorosilicones (FVMQ)
Fluorosilicones fill a critical gap in the performance profile of standard silicone rubber: resistance to nonpolar media. Standard VMQ silicones swell when exposed to fuels, oils, solvents, and hydraulic fluids—fluorosilicones reliably withstand these media without sacrificing the thermal resistance and flexibility of silicone.
This advantage is achieved by introducing trifluoropropyl groups into the siloxane chain. The downside: fluorosilicones are slightly less mechanically robust than standard VMQ and significantly more expensive.
Typical applications: Fuel system seals in the aerospace industry, O-rings for hydraulic systems, diaphragms in the petrochemical and chemical processing industries, seals for turbine fuels (Jet-A, JP-8).
Silicone sponge and silicone foam
Foamed silicones combine the thermal and chemical resistance of silicone rubber with the advantages of a cellular structure: low weight, high compressibility, excellent recovery, and thermal insulation. Depending on the manufacturing process, closed-cell (water-resistant) or open-cell (breathable) structures are produced.
Typical applications: Seals for architectural glazing and facades, shock absorption in transport packaging and electronic enclosures, thermal insulation in EV battery packs, and sound insulation in building services.
EV Battery Trend: Silicone foam has established itself as the material of choice for sealing and thermal insulation in battery packs. Its closed-cell structure offers an excellent combination of IP67-rated sealing, thermal insulation, and vibration absorption—while weighing significantly less than conventional solid rubber seals.
Conductive silicone rubber
By adding special fillers—such as nickel-coated graphite particles, silver particles, or carbon nanotubes—silicones become electrically conductive without losing their basic elastomeric properties. In this way, they address a growing challenge in modern electronics: electromagnetic compatibility (EMC).
Typical applications: EMI shielding gaskets for 5G base stations, servers, and communication equipment; ESD protection components in semiconductor manufacturing; conductive gaskets for battery management systems (BMS); sensor materials for wearable technology.
Thermally conductive silicones (thermal interface materials)
Silicone-based thermal interface materials (TIM) are among the fastest-growing product categories in the entire silicone market. They fill the micro- and macroscopic air gaps between heat-generating components (battery cells, processors, LEDs) and heat sinks—replacing air, which is a poor heat conductor, with a material that has thermal conductivity ranging from 0.4 to over 6 W/m·K.
Available as pre-formed pads, flowable gels, gap fillers, and adhesives, they allow for flexible integration into a wide variety of manufacturing processes.
Typical applications: Battery pack thermal management in electric vehicles (gap filler between cells and the cooling plate), heat dissipation in LED lighting systems, power electronics in photovoltaic inverters and wind turbines, and cooling of 5G infrastructure and data centers.
Silicone Rubber in Electric Mobility: A Market in Flux
The electrification of transportation is the most significant driver of growth for silicone rubber in this decade. From a materials science perspective, a modern EV battery pack is a highly complex system in which silicones perform several critical functions simultaneously.
Thermal Management: The Key to Performance and Safety
The optimal operating temperature for a lithium-ion battery is between 15 °C and 35 °C. Outside this range, performance and service life decline rapidly. At the same time, the thermal management system must control the most dangerous failure scenario—thermal runaway—in which a single cell can heat up to over 800 °C and trigger a chain reaction.
Silicones address both challenges:
During normal operation, thermally conductive gels and gap fillers efficiently dissipate heat from the cells to the cooling system. Their low viscosity allows for automated application in high-volume production, and their permanent flexibility accommodates the battery’s thermal expansion without causing stress cracks.
In the event of a malfunction, thermally insulating silicones prevent heat transfer from an overheating cell to adjacent modules. When exposed to fire, ceramicizing silicone compounds form a ceramic barrier that delays the spread of fire, thereby giving occupants valuable time to evacuate.
Seal: Protection against environmental factors throughout the entire service life
EV battery packs must be hermetically sealed against moisture, dust, and salt spray over a vehicle lifespan of 15+ years—while also withstanding temperature fluctuations ranging from –40 °C to +85 °C and constant vibration.
Automated RTV-2 gaskets (form-in-place and cure-in-place gaskets) have largely replaced prefabricated flat gaskets. They offer more precise geometries, eliminate assembly inaccuracies, and are more easily automated. Silicone foam gaskets are used wherever high compressibility and recovery over tens of thousands of temperature cycles are required.
Electrical insulation and EMI shielding
With operating voltages of up to 800 V in modern EV architectures, the requirements for the dielectric strength of the materials used have increased dramatically. Silicone rubber offers a dual advantage here: high dielectric strength combined with flexibility and temperature resistance—properties that neither epoxy resins (brittle) nor polyurethanes (thermally limited) can provide in this combination.
Conductive silicones with precisely tuned shielding attenuation protect the sensitive electronics of the battery management system from electromagnetic interference.
Why Silicones Are Essential in EV Batteries
Compared to alternative material classes—epoxy resins and polyurethanes—silicones offer significant advantages for EV battery applications:
| property | silicone rubber | epoxy resin | polyurethane |
| temperature range | –60 °C to +250 °C | –40 °C to +150 °C | –40 °C to +120 °C |
| Flexibility / low modulus of elasticity | Excellent | Low (brittle) | Good |
| Fire behavior | Inherently flame-retardant, low smoke | Flammable, toxic fumes | Flammable, toxic fumes |
| UV and weather resistance | Excellent | Good | Limited |
| Automated application | Excellent (FIPG/CIPG) | Good | Good |
Silicone rubber in other key industries
medical technology
Silicone rubber is the preferred elastomer in medical technology—and this trend is growing. Over 72% of cardiovascular, neurological, and orthopedic devices now incorporate silicone components. The reasons: proven biocompatibility, sterilizability (autoclave, gamma radiation, EtO), hypoallergenic properties, and a long-standing track record of clinical success.
The main areas of application include implants and long-term contact products, catheters and tubing systems, breathing masks and valves, surgical instruments, and wearable health sensors. Current development trends are moving toward antimicrobial silicone formulations and nanostructured surfaces for implants.
High-Voltage and Power Engineering
In high-voltage technology, silicones are used for composite insulators, cable joints and terminations, bushing insulation, and transformer seals. Key performance characteristics include the hydrophobicity of the surface (lotus effect, which prevents tracking), tracking resistance in accordance with IEC 60587, and UV stability over decades of outdoor use.
With the expansion of renewable energy and the decentralization of power grids, the demand for silicon components for photovoltaic inverters, wind turbines, and energy storage systems is steadily increasing.
Construction Industry and Building Envelope
Silicone sealants and structural silicone adhesives have been standard components of modern facade and building technology for decades. Structural glazing—the structural bonding of glass panels to metal frames—enables the flush-mounted glass facades that characterize the skyline of modern cities.
Other key applications include weather seals for expansion joints, fire-resistant joint seals, insulating glass seals, and coatings for concrete and natural stone surfaces. The European Energy Performance of Buildings Directive (EPBD) and the focus on energy-efficient construction are driving demand for high-quality sealing solutions.
General Mechanical Engineering and Industrial Applications
Standard seals, O-rings, molded parts, diaphragms, hoses, expansion joints, and damping elements made of silicone rubber form the backbone of industrial maintenance and product development. The material’s versatility—adjustable from 20 to 80 Shore A, available in virtually any color, and resistant to a wide range of media—makes it the material of choice when organic rubbers reach their thermal or chemical limits.
Market Developments and Megatrends in 2026
A market experiencing structural growth
The global silicone rubber market is growing at an average annual rate of 5 to 6 percent and is increasingly shaped by three major trends:
Electrification of transportation: The shift toward electric and hybrid vehicles is fundamentally changing material requirements in the automotive industry. Silicone will not only continue to be needed in existing applications (seals, hoses, cable insulation), but is also opening up entirely new, high-volume application areas such as battery pack sealing, thermal interface materials, and fire protection solutions.
Digitalization and 5G: The increasing power density of electronic systems—from data centers and 5G base stations to autonomous vehicles—is generating more and more waste heat that needs to be dissipated. Thermally conductive silicones and EMI shielding materials are benefiting directly from this trend.
Expansion of renewable energy: Solar panels, wind turbines, battery storage systems, and the associated power electronics require materials that can function reliably for over 25 years under extreme environmental conditions. Silicone rubber, with its UV stability, weather resistance, and thermal resilience, is ideally suited for this purpose.
European Market: Unique Characteristics of the DACH Region
The European silicone rubber market is growing at a CAGR of approximately 5.5% and is projected to reach a volume of over USD 3.2 billion by 2035. For customers in Switzerland, Germany, and Austria, certain regional characteristics are particularly relevant:
Price levels in Europe are structurally above the global average—due to higher energy costs, stricter quality and regulatory requirements, and strong demand from the premium automotive and medical technology sectors. In return, European customers benefit from geographical proximity to top-tier manufacturers (Wacker Chemie in Germany, Elkem Silicones with European sites), shorter supply chains, and a procurement environment with regulatory certainty.
The global market is highly consolidated: The five largest manufacturers—Wacker Chemie, Shin-Etsu Chemical, Dow, Elkem Silicones, and Momentive Performance Materials—together control approximately 70 to 75% of the global market. For European customers, the role of specialized distributors is particularly important: They bring together various manufacturer brands, offer local warehousing with short delivery times, provide support in selecting materials, and ensure compliance with regulatory documentation requirements.
Supply Chain Resilience: Lessons from Recent Years
Experience since 2020 has shown just how vulnerable global supply chains for specialty chemicals can be. For silicone rubber, key risk factors include, in particular, dependence on Chinese silicon metal production, the volatility of energy costs in Europe, and susceptibility to logistics disruptions (container shipping, port bottlenecks).
Forward-thinking procurement organizations therefore rely on multi-sourcing strategies that include at least two qualified suppliers per critical material, a mix of European and Asian sourcing depending on the criticality of the application, strategic safety stocks for supply-critical grades, and active monitoring of raw material markets and regulatory developments.
The Regulatory Landscape in Europe: What Users Need to Know
REACH and the restriction on cyclic siloxanes (D4, D5, D6)
The EU regulation of cyclic siloxanes D4, D5, and D6 is the most significant regulatory development in the European silicone market. These substances—intermediates and unavoidable byproducts of silicone polymerization—have been classified by the European Chemicals Agency (ECHA) as Substances of Very High Concern (SVHC) because they are considered to be very persistent and very bioaccumulative (vPvB).
EU Regulation 2024/1328 provides for a phased schedule of restrictions:
Starting in June 2026, D4, D5, and D6 may no longer be placed on the market as pure substances or in mixtures at concentrations of 0.1% or higher. This applies to both consumer and professional applications, such as cleaning agents, personal care products, waxes, and polishes.
Starting in June 2027, the restriction will be extended to leave-on cosmetic products.
Starting in June 2031, the scope will be expanded to include medical devices and veterinary medicines.
What does this mean for B2B buyers of silicone rubber? Industrial use as a monomer in polymer production remains explicitly exempt. Finished silicone rubber products are generally not affected, provided that the residual levels of cyclic siloxanes are below 0.1%—which is usually the case for high-quality products from European manufacturers. Nevertheless, it is advisable to request current certificates of analysis (CoA) from suppliers with documented D4/D5/D6 residual values—especially for products used in end applications involving direct contact with consumers or patients.
Medical Device Regulation (MDR 2017/745)
The EU Medical Devices Regulation has significantly tightened the requirements for materials used in medical applications. For silicone rubber in medical devices, this means more extensive clinical evaluations, stricter documentation requirements, and complete traceability throughout the entire supply chain—from the silicone manufacturer to the compounder and on to the processor.
Food contact materials
Silicones intended for direct food contact must comply with EU Regulation 1935/2004 (Framework Regulation on food contact materials) as well as any applicable national regulations. In Switzerland, the requirements of food law apply under the supervision of the FSVO (Federal Food Safety and Veterinary Office). Platinum-cured (addition-curing) silicone grades are the preferred choice here, as they do not release any volatile byproducts.
Sustainability and the Circular Economy
In the context of the EU Green Deal and the upcoming Corporate Sustainability Reporting Directive (CSRD), sustainability characteristics are becoming increasingly relevant to procurement decisions, even for technical materials. Silicone rubber presents a mixed picture in this regard.
Among the environmental benefits are the extremely long service life of silicone products (which reduces waste), the absence of plasticizers and halogenated flame retardants, chemical inertness (no leaching of toxic substances into soil or water), and low toxicity in the event of a fire (little smoke, no halogenated gases).
The challenges lie in energy-intensive production, slow biodegradation, and limited opportunities for material recycling. The industry is working on closed-loop systems, more energy-efficient manufacturing processes, and the partial replacement of petrochemical feedstocks with bio-based alternatives.
Choosing Materials: How Do I Find the Right Silicone Rubber?
Choosing the right type of silicone rubber is both a technical and an economic decision. The following questions can help you narrow down your options systematically:
1. What temperatures must the material be able to withstand over the long term?
For applications up to 200 °C, standard VMQ is generally sufficient. For temperatures above 200 °C, specially formulated high-temperature HTV compounds are recommended. For cryogenic applications below –60 °C, special formulations with improved low-temperature performance are available.
2. What media does the material come into contact with?
Standard silicone rubber is resistant to water, many aqueous solutions, UV radiation, and ozone—but not to fuels, oils, and many solvents. Where contact with nonpolar media is unavoidable, fluorinated silicones (FVMQ) are the only viable option.
3. What regulatory requirements apply?
The choice of certification level—industrial, food-grade, medical, or aerospace—determines not only material costs but also lead times, the supplier base, and the documentation requirements. A precise specification prevents the use of over-specified (and thus unnecessarily expensive) materials.
4. What processing method is used?
HTV/HCR for compression molding and extrusion. LSR for injection molding. RTV-1 for manual application. RTV-2 for potting, mold making, and automated sealing systems (FIPG/CIPG). The choice of processing method determines the appropriate type of silicone—not the other way around.
5. What volume is required?
When it comes to high-volume production (millions of units), LSR is virtually unbeatable in terms of cost-effectiveness in injection molding. For small-batch production and prototypes, RTV-2 casting processes or 3D printing with silicone are the more flexible options.
Technological Outlooks
Additive Manufacturing with Silicone Rubber
3D printing with silicone has made significant strides in recent years, evolving from a laboratory curiosity into a production-ready technology. Various processes—ranging from the extrusion of high-viscosity pastes to inkjet-based systems and stereolithography using UV-curing silicone resins—now enable the production of functional prototypes and small-batch parts with material properties that rival those of conventionally processed silicones.
Self-healing silicone elastomers
Basic research is focused on developing silicone elastomers that can partially regenerate after mechanical damage. The underlying mechanisms—reversible covalent bonds, hydrogen-bond networks, or encapsulated healing agents—show great promise but are still in the early stages of development.
Bio-based silicones
Several manufacturers are exploring ways to replace petrochemical feedstocks (particularly methanol) with bio-based alternatives. The challenge lies in ensuring the same product quality and process stability—at competitive costs.
Conclusion
Silicone rubber is no ordinary material—it is a key enabler of major technological trends. From battery technology to medical devices to the energy transition: wherever extreme temperatures, corrosive substances, long service life, and the highest safety standards come together, silicone rubber is the answer.
For engineers, procurement professionals, and product developers in the DACH region, the key to success lies in choosing the right materials—with the support of a knowledgeable partner who not only supplies materials but also provides advice, documentation, and helps navigate regulatory complexities.
SILITECH AG is your Swiss specialist for silicones, adhesives, sealants, and lubricants. We advise you on material selection, ship directly from our warehouse, and support you with technical expertise and regulatory documentation.
Get in touch with us for a no-obligation consultation.
