How We Solved the Problem of Rubber Seal Degradation in an Aggressive Chemical Environment: A Practical Case from the Automotive Industry

Photo: Tahamie Farooqui / Unsplash

In the automotive industry, rubber seals are a key component ensuring tightness and long service life of components. In one of our cases, however, premature degradation of seals occurred in an environment with a high concentration of aggressive chemicals, leading to leaks and complaints. The problem was not in the production itself, but in the material selection, which did not withstand the specific operating conditions. How did we proceed with the analysis and solution search? First, it was necessary to identify the specific chemicals causing the degradation and then select a suitable type of rubber with appropriate chemical resistance.

Problem: Uncontrolled degradation of rubber seals in an aggressive environment

In the automotive industry, rubber seals are a key component for ensuring tightness and long-term functionality of components exposed to chemicals. In our case, the customer faced premature failure of EPDM seals in the cooling system, where the medium was enriched with corrosion inhibitors and glycol-based additives. After several months of operation, significant hardening, cracking, and loss of material elasticity occurred, leading to leaks and the need for frequent replacements.

Analysis revealed that the primary cause of degradation was a combination of oxidative stress and chemical interaction with certain additives in the coolant. Standard EPDM compounds, although resistant to glycols, were not sufficiently stabilized against specific oxidative mechanisms accelerated by high operating temperatures (up to 120 °C). Additionally, microscopic images revealed localized stress cracks caused by uneven swelling of the material due to incompatible additives.

Diagnostics: Laboratory Tests and Identification of Critical Factors

To accurately identify the causes, we conducted a series of laboratory tests according to standard methods for evaluating rubber resistance to liquids. Seal samples were subjected to accelerated aging in a simulated operating environment at temperatures of 100–130 °C for up to 1000 hours. Simultaneously, we tested mechanical properties (hardness, tensile strength, elongation at break) and chemical resistance to individual components of the coolant mixture.

The key finding was that degradation was not caused by the glycol itself, but by specific amine- and phosphate-based additives that accelerated oxidative processes. These substances reacted with the antioxidants in the rubber compound, thereby reducing their effectiveness. Furthermore, we found that the original compound contained an insufficient amount of antiozonants, which led to the formation of surface cracks under dynamic stress.

Photo: Wesley Tingey / Unsplash

Solution: Formulation optimisation and selection of suitable additives

Based on diagnostics, we designed a new EPDM compound formulation with improved resistance to oxidative stress and chemical degradation. The key modification was increasing the content of high-temperature antioxidants based on phenolic and amine compounds, which more effectively block radical reactions. We also added a synergistic combination of antiozonants and UV stabilizers to protect against surface cracking.

To minimize swelling, we adjusted the monomer ratio in the EPDM polymer and added special silane-based additives, which improved compatibility with the coolant. The new compound was tested under real-world conditions for 6 months, with no significant deterioration in mechanical properties or visible defects. Hardness remained stable within a range of ±5 Shore A, which is acceptable for the given application.

Implementation and Long-Term Results: Cost Savings and Increased Reliability

Following successful tests, the new formulation was implemented in the serial production of seals. The customer immediately observed an improvement: the service life of the seals increased from the original 6–8 months to over 24 months without the need for replacement. This led to significant cost savings on maintenance and minimized downtime of the production line.

Long-term monitoring showed that the optimized blend retained its properties even after 3 years of operation. This case illustrates how crucial a detailed analysis of operating conditions and collaboration between raw material suppliers and component manufacturers is. The correct selection of additives and polymers can significantly impact the reliability and economics of industrial applications, particularly in demanding chemical environments.

Photo: Wesley Tingey / Unsplash

Impact of Chemical Resistance of Rubber on Seal Lifespan in Automotive Applications

Rubber seals in the automotive industry face extreme conditions, where a combination of aggressive chemicals, temperature fluctuations, and mechanical stress accelerates material degradation. Typical media that cause problems include engine oils, fuels, brake fluids, or glycol-based coolants. These substances can penetrate the polymer matrix, causing swelling, loss of elasticity, or chemical chain scission. A critical factor is the presence of additives in operational fluids, such as antioxidants, detergents, or corrosion inhibitors, which can interact with rubber components and accelerate their aging.

In practice, degradation manifests as a loss of sealing ability, crack formation, or complete material disintegration. The problem is all the more serious because seal failure often occurs suddenly, without prior warning signs. Automotive manufacturers therefore require materials with guaranteed resistance for 10–15 years or 250,000–300,000 kilometers of operation. The choice of base polymer plays a key role—for example, fluorinated rubbers (FKM) exhibit high resistance to oils and fuels, while nitrile rubbers (NBR) are more suitable for brake fluids. However, the correct selection must also consider economic aspects and processability.

The Role of Additives in Protecting Rubber Seals from Chemical Degradation

Additives play a crucial role in protecting rubber seals from aggressive chemical influences. Their task is to slow down oxidative processes, neutralize acidic or alkaline components of media, or create a protective barrier on the material's surface. The most commonly used include antioxidants, which capture free radicals generated during thermal or chemical stress. Typically, these are sterically hindered phenols or amines capable of interrupting the degradation chain reaction. Another group consists of antiozonants, which protect rubber from cracking caused by ozone exposure, particularly in unsaturated polymers such as natural rubber.

For environments with high oil or fuel content, additives based on metal complexes are proven to enhance resistance to swelling. It is also important to use plasticizers that compensate for the loss of elasticity caused by chemical exposure. However, when optimizing the formulation, attention must be paid to the compatibility of additives with the polymer and among themselves—an unsuitable combination can lead to migration of additives to the surface or their leaching by the medium. The dosage of additives typically ranges from 0.5–5% by weight, with higher concentrations potentially negatively affecting the mechanical properties of the rubber.

Practical Aspects of Testing and Validating New Formulations Under Industrial Conditions

Validating a new rubber seal formulation requires comprehensive testing that simulates real operating conditions. The first step is accelerated aging under laboratory conditions, where samples are exposed to elevated temperatures (typically 70–150 °C) in the presence of aggressive media for several weeks to months. Subsequently, changes in mechanical properties such as tensile strength, elongation at break, or Shore A hardness are evaluated. Another important parameter is the degree of swelling, which must not exceed 10–15% of the original volume to prevent loss of sealing function.

For the automotive industry, specific tests are crucial, such as resistance to engine oils according to manufacturer standards (e.g., tests in oils with varying additive content) or cyclic tests combining chemical and mechanical stress. In practice, testing in real components, such as engine blocks or fuel systems, where long-term functionality is monitored, has also proven effective. Validation must also include an assessment of compatibility with other materials in the system, such as metals or plastics, to avoid undesirable interactions. Only after successfully passing all tests can a new formulation be recommended for serial production.

Need a solution for your applications?

Every industrial application requires an individual approach. GCG Group supplies not only a broad portfolio of additives and raw materials for plastics and rubber, but also technical support including safety data sheets and detailed specifications. Contact us for a consultation on selecting materials resistant to the specific conditions of your operation. Get in touch – or browse our catalog of over 1,300 products right away.