Silicone and EPDM – how ageing affects material durability

The durability of elastomers such as silicone and EPDM is of key importance for the reliability of industrial installations, HVAC systems, automotive applications, and the chemical industry. These materials often operate under demanding conditions: high temperature, humidity, UV radiation, and ozone exposure. Understanding how elastomers age enables effective maintenance planning, proper material selection, and minimization of failure risk.

Why do silicone and EPDM age differently?

Silicone and EPDM differ in their chemical structure, which directly affects their resistance to environmental factors and the mechanisms of ageing.

Silicone is an elastomer based on polysiloxanes, in which Si–O bonds exhibit very high thermal stability and resistance to UV radiation. As a result, silicone retains flexibility even at extreme temperatures and under prolonged exposure to sunlight. At the same time, its structure is more susceptible to swelling and degradation when in contact with oils and certain organic solvents.

EPDM, on the other hand, is a copolymer of ethylene, propylene, and diene, where unsaturated bonds are located in the side chains rather than in the main polymer backbone. This architecture ensures very high resistance to ozone, water, steam, and many chemicals, as the main polymer chain remains saturated and stable. However, EPDM exhibits lower thermal resistance than silicone, and prolonged exposure to elevated temperatures may lead to hardening and loss of elasticity.

As a result, differences in molecular structure cause ageing processes to proceed differently in these materials — silicone performs best under temperature and UV exposure, while EPDM stands out for its resistance to ozone, water, and chemical environments.

What affects elastomer ageing?

The ageing process of elastomers such as silicone and EPDM results from the interaction of various environmental and operational factors. Each of them affects the material differently, leading to changes in polymer structure, loss of elasticity, or degradation of mechanical properties.

Temperature

Temperature is one of the most important factors accelerating thermal ageing of elastomers. The higher the temperature, the faster chemical reactions occur in the material — primarily oxidation and polymer chain scission. In practice, this leads to hardening, loss of elasticity, and a decrease in strength.

Silicone, due to stable Si–O bonds, withstands high temperatures very well and can operate even at 200°C without rapid loss of properties. It ages more slowly, and changes usually occur only after long-term exposure.

EPDM has good thermal resistance, but lower than silicone. At temperatures above approximately 120°C, the material begins to harden more rapidly and lose elasticity due to oxidation and additional crosslinking processes.

Even a slight increase in temperature can significantly reduce the lifespan of an elastomer; therefore, kinetic models such as the Arrhenius curve are used to assess durability and predict ageing rates under different operating conditions.

Ozone

Ozone is one of the most aggressive factors accelerating ozone ageing of elastomers. As a strong oxidizing agent, it reacts with double bonds in the polymer structure, leading to the formation of characteristic fine cracks on the material surface.

Elevated ozone concentrations occur mainly:

• near electrical equipment that can generate small amounts of ozone during operation (e.g., transformers, motors, high-voltage devices),
• outdoors, where ozone is naturally formed under UV radiation and photochemical reactions in the atmosphere.

Under such conditions, elastomers are exposed to faster cracking and surface degradation. Due to its saturated main chain, EPDM is one of the most ozone-resistant materials, while other elastomers may require additional protection or stabilizers.

UV radiation

Ultraviolet radiation is one of the main factors accelerating UV ageing of elastomers. The energy of UV radiation — especially in the UVC range and so-called vacuum UV — causes photolysis, i.e., the breakdown of chemical bonds in the polymer structure. As a result, the material gradually loses elasticity, becomes brittle, may change color, and exhibits a clear decrease in mechanical properties.

Elastomers exposed to UV are also more susceptible to oxidation; therefore, in the presence of ozone, degradation proceeds even faster. For this reason, materials used outdoors or in areas with high exposure to sunlight must have appropriate UV stability — silicone performs exceptionally well here, while other elastomers may require protective additives or special compounds.

Other factors affecting elastomer ageing

In addition to temperature, ozone, and UV radiation, other chemical and physical factors also influence elastomer ageing. Contact with oils, fuels, or aggressive media may lead to swelling, leaching of additives, or degradation of the polymer structure — particularly in the case of silicone, while EPDM performs well in aqueous and chemical environments. High humidity and steam can accelerate hydrolysis and oxidation processes, while long-term mechanical loads such as compression, vibrations, or cyclic stresses cause stress relaxation, creep, or cracking. These factors often act simultaneously, intensifying ageing effects and accelerating the loss of material properties.

Effects of premature material ageing

Premature ageing of materials leads to a number of negative consequences affecting both their properties and the reliability of entire systems. As the polymer structure degrades, components harden, lose elasticity, crack, or change dimensions, which may result in leakage and failures. Over time, this leads to the need for more frequent component replacement, increased maintenance costs, and the risk of unplanned downtime. Therefore, understanding the effects of ageing is crucial for proper material selection and ensuring long, failure-free system operation.

High-quality silicone and EPDM products available at Power Rubber

At Power Rubber, we offer high-quality silicone and EPDM products distinguished by excellent resistance to environmental conditions and long service life. Proper material selection, combined with correct maintenance and operation, allows for a significant extension of seal lifetime and reduction of failure risk.

If you are looking for durable, resistant, and reliable solutions, choose materials that withstand demanding operating conditions. Contact us by phone at +48 22 292 40 24 or +48 505 16 03 03, by email (Power@PowerRubber.com), or via our contact form to select suitable silicone or EPDM products and ensure longer service life and higher safety for your installations.