Critical considerations regarding thickness and safety in railway weatherstripping
On numerous occasions, EN 45545-2 certification is accepted as valid without reviewing in detail the conditions under which it was issued. However, in the field of rubber foam and cellular rubber processing, it is common to find materials—especially those from distant sources—accompanied by fire and smoke tests that do not adequately represent the actual performance of the product.
The main technical risk does not lie in the age of the documentation (although this should not exceed 5 years), but in the incorrect extrapolation of the certified thickness.. A test conducted on 3 mm does not guarantee compliance when the final part is manufactured in 8 mm, 10 mm, or more.
Why does a 3 mm certificate not validate a 10 mm material?
The technical limitation of thickness and combustible mass
Chloroprene-based synthetic rubbers are combustible materials. When a laboratory certifies a “thin” sample, it evaluates a specific amount of combustible mass and smoke generation. Assuming that this result is applicable to greater thicknesses is an engineering error with direct consequences for safety:
- Greater thickness = greater combustible mass
As thickness increases, the amount of material involved in combustion increases significantly. - Increased heat and smoke opacity
The heat input and smoke density tend to exceed the limits defined by EN 45545-2 for HL2 classification.
Basing the selection of a weatherstrip or seal on a test conducted on a lower thickness poses a clear risk to passive safety in the rail vehicle.
ZF 703: cellular synthetic rubber (CR-M) with guaranteed compliance
To eliminate uncertainties, ZFoam has developed grade ZF 703, a chloroprene cellular rubber (CR-M) designed specifically for railway applications. The material has undergone updated testing that certifies its compliance with EN 45545-2, classification HL2 in R23 and R24, for thicknesses of up to 10 mm.
This technical coverage is suitable for most of the sealing and cushioning applications in ceilings, windows, doors, panels, and electrical boxes in both surface and underground trains.
Additional technical features
Long-term durability, stability, and sealing
Beyond its fire performance, a synthetic rubber for railway use must maintain its properties over a long-life cycle and in demanding environmental conditions.
The key properties of ZF 703 include:
- High resistance to weathering and aging
The chloroprene-based formulation provides excellent resistance to ozone, UV radiation, and thermal variations, preventing cracking and premature degradation. - Low water absorption (< 5%)
Its closed-cell structure prevents moisture accumulation, reduces the risk of corrosion in metal components, and prevents microbiological proliferation. - Excellent elastic recovery (Compression Set)
It maintains its sealing capacity after prolonged compression cycles, ensuring the airtight closure of doors, hatches, and moving parts.
Manufacturing adaptability. From sheet to final part
ZF 703 is designed to be easily integrated into industrial production processes. It is available in:
- Thickness: from 2 mm to 50 mm (fire certification guaranteed up to 10 mm).
- Formats: sheets, machined weatherstripping, die-cut gaskets, and CNC parts.
- Adhesive options: acrylic adhesives with different liners to facilitate installation on site.
The importance of requiring a complete test report
The railway sector is moving towards increasingly stringent requirements. Verifying the exact thickness assessed is essential to ensure the actual conformity of the material.
An inadequate certificate can compromise the approval of the project and, more importantly, the safety of the vehicle.
For applications that demand reliability, traceability, and demonstrable compliance, ZF 703 represents a safe and consistent technical solution.
Do you need to validate this material for your next project? Download the ZF 703 technical data sheet or contact our team.
