As the subdivision of the safety classes into their range of application multiplicates the amount of plastic needed, with the thermosets BMC 0204 and SMC 0208 the Lorenz Kunststofftechnik GmbH developed material that comply with the new provisions.
Common causes of fire in trains are intentional or negligent arson as well as malfunctions of the electric system. Fire risks and their consequences are of highest importance in public transportation. The possibility to exit railway vehicles in the case of fire as safely as possible is a decisive factor of safety. “Other requirements apply in railway vehicles than in buildings, other plastics have to be used”, explains Thomas Lorenz, managing director of the Lorenz Kunststofftechnik GmbH. “These fire protection standards pose difficulties for manufacturers of material and components.” Yet, national fire protection regulations apply as for example the NF F 16-101 in France or the German DIN 5510. The new DIN EN 45545-2 shall now regulate and standardise the fire protection requirements on an European level so that the interoperability in the trans-European high-speed traffic as well as the safety of rail passengers is being guaranteed. The existing fire protection standards for railway vehicles of the international railway traffic and various European states are the basis for this, whereby the requirements depending on the country will be tightened in comparison to the previous regulations.
Flame resistance, sustainability and longevity for inside and outside
The thermosets BMC 0204 and SMC 0208 have been designed to the broad range of new requirements in rail vehicle construction with regard to their mechanical properties and flame retardant behaviour and as one of the first passed the fire protection test in conformity with CEN/TS 45545-2.
In the focus of the new material test procedures are – next to the flammability and flame dispersion – in particular, the inspection of the development of smoke gas, the density of smoke and the toxicity of the smoke. These parameters demand a change of the material development for which poor degradation kinetics are necessary. In the future, thermoplastics, the most commonly used material in rail vehicle construction, will not fulfil the high standards in all areas due to their poor mechanic and thermic properties. They show a too extensive smoke development and due to their low softening point melt too quickly. Especially with critical parts such properties may become a risk for passengers. Therefore, the new standards consider flammability and flame dispersion (ISO 5668-2), the thermal release rate (ISO 5660-1) and smoke gas density as well as the toxicity of the smoke gas (ISO 5659-2) for the classification of the fire behaviour and fire side effects.
To calculate the Hazard Level (HL), on which the requirements of the classification system are oriented, the operating and construction categories in conformity with DIN EN 45545-2 are being used. Currently, the requirements are being assigned in 26 tiers (R1-R26). Depending on the range of application of the material or parts within a construction, the form and the arrangement of the material as well as the directly exposed area various fire protection tests and results are required. For example, the material is differenced into generally accessible and not accessible areas, based on their general range of application inside or outside the train and their specific usage, for example, for furniture, electrotechnical and mechanic facilities. Surfaces made of SMC, for example, have been approved for the highest HL tier (HL3).
SMC is available as semi-finished product in rolls and is used where high mechanical strength and stiffness is required. In the rail sector the plastic is foremost used for the exterior and interior cladding, window frames, seats and hubcaps. BMC is especially suitable for the production of small parts, for example, light switches or electrical plug connections as it can be used / manufactured by the processes of compression moulding, injection moulding, transfer moulding and injection-compression moulding. Due to its CTI values of 600 volts and a thermal conductivity of 1,35 W/mK it can also be used for electronic components.
The various fields of application of BMC and SMC in all risk levels contribute to reduce the amount of material used in the rail vehicle construction and therewith the expense for the production and warehousing. With regard to the trend to enhance increasingly more plastic components for weight, design and comfort reasons, the thermosets from Lorenz, additionally, provide options for further light constructional components in the construction of multiple unit trains and carriages as well as other vehicles or aircrafts thanks to their advantageous fire behaviour.
Companies: Lorenz Kunststofftechnik GmbH
Industries: Railway Vehicles & Infrastructure