European railway standards and elastomeric materials: what actually changes in 2026

For decades, the European railway regulatory framework has provided a relatively stable foundation for component design. Long approval cycles, the reuse of previously validated solutions and platform continuity have allowed many materials to remain in service without substantial modification for years. However, this equilibrium is beginning to break down as the system stops absorbing inconsistencies between regulation, design and real-world operating conditions.

2026 does not introduce an abrupt regulatory shift, but it does consolidate a change in approach. From this point forward, tolerance for materials designed under legacy assumptions is significantly reduced. Elastomeric components—and silicone-based ones in particular—now sit in a critical zone where documentary compliance is no longer sufficient without long-term technical coherence.

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Railway

Fabricación de componentes y juntas de silicona con certificaciones EN 45545 y resistencia al fuego para el sector ferroviario.

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1. EN 45545-2: from familiar requirement to integrated enforcement

EN 45545-2 is not new. Its fire, smoke and toxicity performance requirements have been mandatory in European rail for years. What effectively changes in 2026 is not the content of the standard, but how compliance is enforced.

The expiry of certain transitional periods eliminates acceptance of partial certifications, historical equivalences or validations disconnected from the final component. Going forward, the elastomeric material, its formulation, component geometry and actual service conditions are assessed as a single technical system. This integration has direct consequences for silicone.

The real impact of flame-retardant reformulations

Achieving certain hazard levels—particularly HL2 and HL3—requires formulation changes that are not mechanically neutral. The addition of flame-retardant fillers, adjustments to the crosslink network or catalyst changes alter the original elastomer balance.

In non-optimised formulations, the following effects are commonly observed:

• Effective hardness increases in the range of +3 to +6 Shore A
• Elongation at break reductions of 5 to 15%
• Higher compression set under sustained load
• Increased density due to mineral filler incorporation

These effects do not invalidate the material, but they do require component design to account for them from the outset. When this does not happen, regulatory compliance may be achieved at the expense of functional reliability.

2. Comparative analysis: standard silicone vs. EN 45545-2 silicone

To illustrate the real impact of reformulation, it is useful to compare general-purpose silicone grades with grades specifically developed for railway compliance. The following data correspond to actual industrial formulations at 60 Shore A, processable by both extrusion and moulding:

Technical interpretation

What this comparison reveals is significant: a properly developed EN 45545-2 formulation not only maintains baseline mechanical properties, but can actually improve them. The increase in tensile strength (+20%) and elongation (+12.5%) indicates that the formulation work has actively compensated for the effect of flame-retardant fillers.

However, two aspects require attention:

• Increased density: The density increase (up to +10%) reflects the incorporation of mineral flame-retardant fillers. This has implications for component weight and, potentially, dynamic behaviour under vibration.
• Colour limitations: Flame-retardant formulations have colour restrictions. Pigments can interfere with fire performance, so options are typically limited to black (RAL 9017), blue-black (RAL 5004), grey and cream.

3. Fire test results: what they actually mean

Silicone components for railway applications must pass specific tests according to EN 45545-2. The critical parameters are:

Data interpretation

Limiting Oxygen Index (LOI): Values above 32% are required to achieve HL3. The values of 32.7% (extrusion) and 35.1% (moulding) meet this threshold with margin. The difference between processes reflects variations in crosslink structure.

Specific Optical Density (Ds max): The value of 45 for moulding versus 84.7 for extrusion is notable. Both are well below the HL3 limit of 150, but the difference suggests that the moulding process generates a more thermally stable structure.

Conventional Index of Toxicity (CIT_PNL): Values of 0.06 against an HL3 limit of 0.75 indicate extremely low toxic gas emissions, an inherent characteristic of well-formulated silicones.

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4. The gap between laboratory validation and in-service performance

One of the most sensitive aspects of the 2026 transition is the time lag between validation and failure. In many cases, silicone components reformulated for EN 45545-2 compliance pass laboratory tests without difficulty. The documentation is correct, reports are in order and the component is approved for installation.

The problem appears years later. In service, under constant compression and moderate temperatures (60–80°C in interior or technical zones), the material begins to exhibit excessive permanent deformation. A compression set initially below 20% can exceed 25–30% after several thousand hours, compromising sealing or acoustic function.

Factors accelerating degradation

• Insufficient post-cure: Residual volatiles affecting the crosslink network
• Non-optimised flame-retardant fillers: Interference with the vulcanisation process
• Uncontrolled shrinkage: Internal stresses of 2–4% in HCR that manifest over time
• Thermal hardness variation: +3 to +5 Shore A per 50°C increase

When this occurs, the problem shifts from regulatory to operational. The fix no longer involves adjusting a formulation during development, but intervening on installed components—at far higher cost and with reduced room for manoeuvre.

5. TSI evolution and the changing technical context for rolling stock

The Technical Specifications for Interoperability do not establish direct requirements for elastomers, but they do redefine the environment in which these materials operate. Recent updates, particularly for freight rolling stock, reinforce demands for reliability, stability and service life across the entire train.

From a silicone materials perspective, this translates into more demanding thermal cycles, prolonged vibration exposure and tighter functional tolerances.

The consequence is cumulative. This is not about sudden failures, but progressive performance degradation that ultimately affects overall system functionality.

6. System densification and evolving service conditions

The evolution of control and signalling systems, with the progressive rollout of ERTMS and denser radio-based architectures, indirectly modifies operating conditions for many elastomeric components.

The increase in cabling, cable grommets and seals in technical zones raises local temperatures and extends thermal exposure time. For silicone, this factor is critical.

Thermal hardness behaviour

The variation in hardness with temperature—typically +3 to +5 Shore A per 50°C—can push the material outside its functional window if not anticipated during design.

Designs that were perfectly valid under previous architectures are beginning to show limitations—not because they were poorly conceived, but because they respond to a technical context that no longer exists.

7. Material selection: technical criteria by application

Selecting the right material requires considering multiple factors simultaneously. The following matrix guides decision-making based on primary requirements:

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Note on cross-certification

It is important to note that certifications are not always mutually compatible. For example:

• EN 45545-2 formulations do not carry food-contact certification
• RAL colourants may invalidate certain certifications
• Electrically conductive silicones are only available in black

8. Recurring errors in the transition to 2026

As 2026 approaches, familiar patterns are beginning to repeat:

• Reuse without traceability: Historically accepted materials are reused without verifying that the current formulation maintains original properties.
• Reformulation without redesign: The material is modified for EN 45545-2 compliance but the original component geometry is retained, without compensating for changes in mechanical properties.
• Validation disconnected from production: Tests are performed on laboratory prototypes whose process conditions are not replicated in series production.
• Incomplete specification: 'EN 45545-2 silicone' is specified without stating HL level, R requirement, validated thickness or transformation process.

These are not regulatory failures. They are failures of technical approach. The standard does not demand more than it always has, but the system no longer absorbs inconsistencies between design, material and real-world use.

9. Components most exposed to the new landscape

The elastomeric components most sensitive to this evolution are those combining critical function with extended service presence:

• Door and cab seals: Sealing function + opening/closing cycles
• Interior sealing profiles: Temperature exposure + permanent compression
• Cable grommets: Cable protection + system densification
• Elastomeric guards: Mechanical function + environmental exposure
• Secondary anti-vibration mounts: Dynamic loading + thermal ageing

In all these cases, the material cannot be evaluated as an isolated laboratory reference, but as part of a functional system that must maintain its performance over one or two decades.

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10. Recommendations for specifiers and designers

For new developments

• Specify completely: State HL level, applicable R requirements, minimum validated thickness and transformation process (extrusion/moulding)
• Request ageing data: Not just initial properties, but behaviour after thermal exposure and long-term compression set
• Consider density: Weight increase may be relevant in mass-sensitive applications
• Validate colour: Confirm that the required colour is available without compromising certification

For components in service

• Audit traceability: Verify that materials in use correspond to currently certified formulations
• Establish degradation indicators: Define objective end-of-life criteria before functional failure occurs
• Plan replacements: Identify critical components and ensure availability of certified spares

Conclusion

European railway regulation has not suddenly become more stringent. What has changed is the margin for error. In 2026, compliance will still be necessary, but it will no longer be sufficient. The difference between a reliable component and a problematic one will not lie in the certificate, but in how the material was designed to age under real service conditions.

The technical data presented in this article demonstrate that it is possible to develop EN 45545-2 formulations that not only meet fire requirements, but maintain—and even improve—mechanical properties compared to standard silicones. The key lies in formulation work and coherence between material, process and application.

Anticipating this reality is an engineering decision. Ignoring it is accepting operational risk.