Selecting the ideal material for industrial sealing solutions comes down to the specific environmental conditions that the seal will be exposed to. Two of the most popular contenders for sealing solutions in a wide variety of industries are General Purpose Silicone Rubber and EPDM Rubber. Both are high-performance materials offering distinct advantages, particularly for use in outdoor applications where resistance to weather and elements like ozone and UV are key. However, when the application heats up, the differences in characteristics between these two materials become all the more important.

For engineers or procurement specialists making decisions on gasketing and sealing materials, when it comes to choosing between Silicone and EPDM, understanding their specific thermal resistance capabilities is vital for preventing seal failure.

Let’s take a deep dive into the key specifications of Silicone Rubber and EPDM Rubber, to determine which is the better choice for high temperature sealing applications.

EPDM Rubber: Key Specifications

EPDM (Ethylene Propylene Diene Monomer) Rubber is often chosen for its impressive weathering capabilities, particularly in the automotive and construction industries, for applications such as window seals, roofing membranes, and a wide range of outdoor gaskets.

Standard EPDM is designed for moderate temperatures, operates effectively within a wide temperature range of -30°C to +80°C, whilst specialist grades can push the upper temperature limit, for example, LSLT EPDM (Low Smoke Low Toxicity) operates within -30°C to +100°C.

Strengths

Despite moderate temperature limitations compared to some other elastomers, EPDM exhibits strong characteristics that make it a strong choice for many applications:

• Weathering: It offers outstanding resistance to ozone, UV light, and general weather conditions (including rain and frost).
• Chemical resistance: EPDM shows good resistance to water-based chemicals and vegetable-based hydraulic oils, making it ideal for automotive braking systems and water handling.
• Durability: It is known for good tensile strength and a low compression set, meaning it recovers well after being compressed.

Whilst EPDM is a durable and weather resistant material, for applications involving an environment where temperatures can exceed +80°C (or +100°C for LSLT), it begins to degrade, leading to seal failure.

Silicone Rubber: Key Specifications

General Purpose Silicone Rubber is a popular choice for a range of extreme environments. It’s an inert material, meaning it doesn’t react with most chemicals, and as a result is widely used in industries ranging from food and drink processing to mass transit and aerospace.

The thermal resistance of Silicone is often a key consideration for engineers, as it is capable of operating under extreme temperatures between -60°C and +230°C, whilst specialised grades such as HT200 can withstand temperatures of up to +250°C, whilst maintaining structural integrity.

Strengths

The most notable strengths of General Purpose Silicone include:

• Extreme heat performance: With a standard upper limit of +230°C, silicone can survive in environments that would melt or significantly degrade EPDM.
• Inertness and safety: Most grades of solid silicone are food safety compliant and WRAS (Water Regulations Approval Scheme) approved, making them safe for food, drink, and potable water contact.
• Longevity: General Purpose Silicone has a long life span, and maintains excellent resistance to ozone and UV, much like EPDM.

Making the Right Choice

For applications involving sealing engine compartments, industrial ovens, or steam processing lines, EPDM Rubber is most likely insufficient due to the limitations of the material’s temperature resistance. However, EPDM is well suited to applications where weather resistance is essential, but heat is more moderate.

In contrast, Silicone performs strongly when exposed to heat, whether General Purpose or a specialised grade. At over +200°C, Silicone remains flexible and maintains its sealing ability, whereas EPDM would fail under the same conditions.

While Silicone certainly wins on temperature, when cost and specific chemical compatibility are also factors, EPDM can be a cost-effective choice and has strong resistance to certain oils that may damage Silicone. However, for applications where the primary threat to sealing ability is heat, Silicone Rubber is the go to choice.

Your Next Project

If you are considering the right gasket or sealing material for your next project, talk to CB Frost & Co. Our experienced sales team will be able to help you choose the best suited and most cost-effective material specifications for your intended application.