Silicone Rubber Elastic Modulus: Properties, Comparisons, and Applications

If you’re working with silicone rubber, you need to understand its modulus of elasticity. This is a measure of how flexible or stiff a material is. This guide will help you understand what the silicone rubber elastic modulus is, how to measure it, and why it’s important. 

You’ll also learn about typical values, the main factors that influence it, and how silicone rubber compares to other types of elastomers. With this knowledge, you can choose the right type to suit your needs.

What Is the Elastic Modulus of Rubber and Silicone?

What is Silicone Rubber?

Silicone rubber is a synthetic elastomer made from silicon, oxygen, carbon, and hydrogen. It is known for its good heat resistance, chemical resistance, and flexibility over a wide temperature range. You will often find silicone rubber in the medical, automotive, electronics, and food industries. Its performance depends largely on the formulation and curing method.

Unlike natural rubber, silicone rubber remains flexible even at very high or very low temperatures. It is resistant to UV rays, ozone, and moisture, making it ideal for harsh environments. Its unique molecular structure helps silicone maintain stable mechanical properties over time, including elasticity. This is a key factor when evaluating silicone rubber elastic modulus in long-term performance applications.

Before learning about what is the elastic modulus of rubber, you need to understand what makes silicone rubber so good. The molecular structure and degree of cross-linking are key factors in determining how hard or soft a material is.

Silicone Elastic Modulus Explained in Context

The silicone modulus of elasticity—also known as Young’s modulus—measures how stiff a material is when subjected to tensile or compressive forces. For silicone rubber, this indicates how stiff or soft the material is when deformed.

Typically, the modulus of elasticity of silicone rubber ranges from 0.1 MPa to 10 MPa, depending on the manufacturing formula. Low values ​​indicate a softer, more flexible material. High values ​​indicate a stiffer, less deformable material.

Compared to other rubbers, silicone has a moderate modulus, but it performs well in harsh conditions. It retains its elasticity when exposed to high temperatures, deep cold, or harsh chemicals. Therefore, silicone is often used for gaskets, seals, pipes, and flexible parts that require long-term durability.

When choosing a silicone, you need to consider the modulus of elasticity carefully. It directly affects the product’s ability to bend, be elastic and retain shape.

Silicone Rubber Modulus: Typical Values and Influencing Factors

Standard Modulus Ranges

Depending on the type of silicone rubber you use, the modulus of elasticity will vary significantly. The three common types are:

• LSR (Liquid Silicone Rubber): typically has a lower modulus, is more flexible, and is ideal for parts that require high flexibility.
• RTV (Room Temperature Vulcanizing): is used in adhesives and sealants and comes in a variety of hardnesses.
• HTV (High Temperature Vulcanizing): typically has a higher modulus, and is suitable for applications that require high mechanical strength.

Typical modulus values ​​range from 0.1 MPa to 10 MPa, depending on the formulation, cure rate, and fillers. This level of silicone rubber elastic modulus will partly determine which type you should choose for your product.

What Affects Silicone Rubber Elastic Modulus?

Many factors can alter the elastic modulus of silicone rubber. Here are the main ones:

• Molecular structure: long polymer chains and low cross-link density produce softer silicones.
• Filler content: Adding silica or other fillers can increase modulus and hardness.
• Cure rate: A more aggressive cure often results in a harder product.
• Type of additives: Some additives increase tensile strength, while others soften the material.

When developing your product, you need to clearly define the requirements for hardness, elasticity, and environmental conditions to choose the right silicone formulation.

Comparing Silicone Rubber Modulus with Other Elastomers

When selecting materials for your products, it is important to understand the differences in silicone rubber elastic modulus between silicone rubbers. Let’s compare the performance of this material with that of a few other elastomers.

Silicone Rubber vs EPDM

Silicone rubber and EPDM (Ethylene Propylene Diene Monomer) are two widely used synthetic elastomers, each with distinct properties that make them suitable for specific applications.

• Temperature range:

Silicone rubber can withstand a wide range of temperatures, from about -60°C to 230°C or even up to 300°C. EPDM works best between -50°C and 130–150°C, but becomes brittle below -40°C.

• Chemical and water resistance:

EPDM is very good at resisting water, acids and alkalis, making it suitable for harsh outdoor and industrial environments. Silicone is resistant to many chemicals but less so to acids and alkalis. However, some specialty silicones are more resistant to oil than EPDM.

• Mechanical properties:

EPDM has better tear and abrasion resistance, along with higher tensile strength, making it durable in harsh working conditions. Silicone is more flexible, especially at low temperatures, and retains its properties over a wider temperature range, but has lower abrasion resistance.

• Weather and UV resistance:

Both materials have good resistance to weather, UV and ozone. EPDM is preferred for long-term outdoor applications due to its superior UV and water resistance.

• Cost and sustainability:

EPDM is cheaper and more recyclable, making it suitable for large projects or those with limited budgets. Silicone is more expensive and requires specialized recycling, but has the advantage of flexibility and heat resistance.

Summary:

→ Our recommendation:

• Choose EPDM if you need weather, water, acid or abrasion resistance at a low cost. 
• Choose silicone rubber if high flexibility, extreme temperature resistance or oil resistance and food and medical safety are a priority.

Silicone Rubber vs Natural Rubber

Natural rubber is extracted from the latex of the rubber tree (Hevea brasiliensis), mainly consisting of organic polyisoprene chains. Meanwhile, silicone rubber is a synthetic material made from silicon-oxygen (Si-O) bonds with adjacent organic groups, bearing an inorganic chemical structure.

Performance assessment:

• Heat resistance: Silicone rubber can withstand much higher temperatures (up to 230–250°C), while natural rubber begins to degrade above 80°C and melts at around 120°C. Both retain flexibility at very low temperatures (down to -50°C).
• Mechanical strength: Natural rubber has excellent tensile strength, tear and abrasion resistance, making it suitable for high-wear applications such as tyres and conveyor belts. Silicone rubber is flexible but less resistant to abrasion.
• Weather and UV resistance: Silicone rubber has excellent resistance to weathering, ozone and UV, making it suitable for outdoor use as gaskets and seals. Natural rubber is susceptible to deterioration when exposed to sunlight and ozone.
• Chemical resistance: Silicone rubber is resistant to many chemicals, especially ozone and grease, but not to hydrocarbon fuels and strong acids/bases. Natural rubber is susceptible to grease, ozone but is more resistant to water and weak acids.
• Biodegradability and environmental impact: Natural rubber is biodegradable, environmentally friendly. Silicone rubber is sustainable but not biodegradable.
• Medical and food applications: Silicone rubber is biocompatible, hypoallergenic, suitable for medical and food products. Natural rubber can cause allergies and is less suitable for these applications.

Key properties comparison

→ Our recommendations:

• Choose natural rubber if you need high strength, elasticity, good abrasion resistance, biodegradability and low cost, especially for indoor or high abrasion applications.
• Choose silicone rubber when high or low temperature resistance is required, outdoor use or UV exposure is required, chemical resistance is required, medical/food applications or long lasting durability is required.

Silicone Rubber vs TPE (Thermoplastic Elastomer)

Silicone rubber is a synthetic elastomer with a silicon-oxygen skeleton structure, which is characterized by excellent heat resistance, chemical inertness and high biocompatibility.

TPE (Thermoplastic Elastomer) is a group of copolymers or blends that combine the elasticity of rubber with the processability of thermoplastics. TPE is favored for its flexibility, recyclability and convenience in production.

Performance assessment:

• Heat resistance: Silicone rubber can withstand high temperatures and remains stable in extreme cold temperatures, suitable for demanding environments such as automotive, aviation, and sterile medical equipment. Its silicone rubber elastic modulus provides the necessary flexibility and durability to maintain performance under these conditions. Meanwhile, TPE can withstand moderate temperatures but is susceptible to deformation when exposed to high temperatures, limiting its application in hot environments.
• Chemical and environmental resistance: Silicone is very resistant to water, oxidation, ozone, and many chemicals, but less resistant to hydrocarbon fuels and strong acids/bases. TPE is resistant to water, grease, and some solvents but less resistant to strong chemicals and prolonged UV light.
• Biocompatibility and safety: Silicone is preferred in medical and food applications due to its high biocompatibility and low allergenicity. TPE is safe for many consumer products and some medical devices but is less biocompatible than silicone and is not suitable for long-term contact with the body.
• Durability and aging: Silicone has a slow aging rate and excellent resistance to UV rays, ozone, and weather. TPE ages faster, especially when exposed to harsh environments.
• Processing and sustainability: TPE is a thermoplastic that can be melted and reformed many times, making it very friendly to sustainable manufacturing processes. Silicone requires a complex vulcanization process and is difficult to recycle, which is a limitation in projects that prioritize sustainability.
• Cost and manufacturing: TPE is low cost, easy to process, suitable for large-scale production and cost savings. Silicone is more expensive and has a complex manufacturing process, but it compensates with superior performance in harsh conditions.

Summary:

→ Our recommendations:

• Choose silicone rubber when high heat resistance, chemical inertness, biocompatibility and long-term durability are required.
• Choose TPE when softness, flexibility, recyclability, low cost and simple processing are preferred.

How to Choose the Right Modulus for Your Needs?

When working with silicone rubber, one key factor that often comes up is silicone rubber elastic modulus — basically, how stiff or flexible the material is. Picking the right modulus can make a huge difference in how your product performs, fits, and lasts.

Let’s break down what you need to know to choose wisely.

• Application needs

If you want a silicone product that is highly stretchable, bendable, or shock-absorbing, choose a low modulus silicone. Examples include rubber gaskets, washers, or vibration dampers — things that need to be flexible and easy to install.

Conversely, if the product needs to retain its shape, withstand pressure, or resist extrusion, a high modulus silicone is a good choice. Applications like engine mounts, support pads, or high-pressure gaskets often use this type.

• Assembly and handling

If your part needs to stretch or fit into a tight space, a low modulus silicone will make installation much easier. Or else, if the part needs to retain its shape or resist extrusion, choose a high modulus silicone.

• Performance when bearing force

High hardness silicone will withstand large impacts, avoiding permanent deformation or extrusion.

Meanwhile, low hardness silicone will show its strengths when absorbing vibration, impact, or where high flexibility is required.

• Environmental and mechanical requirements

The hardness of silicone changes with temperature — it will usually decrease as the temperature increases. Therefore, choose the appropriate hardness to ensure the product operates stably in the expected temperature range of use.

In addition, factors such as chemical exposure, crosslinking level, and fillers (such as carbon black) also affect hardness. Consider choosing the right silicone for your environment and usage conditions.

Silicone Rubber Elastic Modulus – Conclusion

There is no single answer to the silicone rubber elastic modulus hardness. If you need flexibility, ease of installation, and shock absorption, choose a low-modulus silicone. Conversely, if the part needs to be rigid, retain its shape, and resist deformation under pressure, a high-modulus silicone is the best choice.

Always consider the specific requirements of the application and consult the data sheet to find the most suitable silicone. If you are looking for a partner with experience in processing silicone rubber to the required hardness, TOGOHK can provide flexible and reliable solutions for your industrial projects.