Kraiburg TPE has introduced the FR3 series, its third generation of halogen-free, flame-retardant thermoplastic elastomers designed for environments with stringent fire protection requirements, particularly in rail vehicles. The compounds meet the specifications of DIN EN 45545-2 for railway applications, including R22 HL3 and R23 HL3. In addition to fire behavior, the series targets functional performance in demanding uses such as cable management components, cable glands and seals. Reported properties include very good tear resistance for halogen-free, flame-retardant TPEs, improved resilience versus previous generations, and favorable compression set values. The materials demonstrate strong performance in the 23 to 70 °C range, which supports sealing applications. For multi-component constructions incorporating polyolefins, the series is formulated for PP adhesion and is compatible with standard injection molding and extrusion. Owing to their thermoplastic structure, production scrap such as cold runner material and single-component defective parts can be reprocessed and returned to in-process recycling streams.
Fire performance and certifications
The FR3 compounds address current rail sector requirements for halogen-free materials, which aim to minimize smoke toxicity in the event of a fire. Low smoke density and toxicity are verified by tests referenced in railway standards. In the UL94 vertical burning test, the series achieves a V0 classification at 1.5 mm thickness, indicating self-extinguishing behavior under test conditions. These results are recognized under the UL certification program, enabling issuance of a Yellow Card as evidence that the defined safety, quality and performance criteria for TPE have been met.
In addition to UL94 performance, the series passes the glow wire test at 960 °C without flame formation, addressing risks associated with overheating of live electrical components. According to the company, the FR3 formulations fulfill the relevant railway-related fire requirements across all color and hardness variants.
Material characteristics and use in rail systems
Beyond fire behavior, the FR3 series is intended for components in energy supply systems on rail vehicles, where high material robustness is required. The compounds provide very good tear resistance for halogen-free, flame-retardant TPEs and improved resilience compared with their predecessors, particularly between 23 and 70 °C. These parameters support typical sealing functions in areas such as cable management and ingress protection. Processing is designed for established thermoplastic methods, namely standard injection molding and extrusion, including overmolding with polyolefins where excellent adhesion to PP is required. The thermoplastic nature of the materials allows recovery of cold runner distributors and single-component defective parts for in-process recycling.
Johanna Schmid, market specialist for industrial applications at Kraiburg TPE, said: "Thanks to their low smoke toxicity, our halogen-free, flame-retardant TPEs improve safety and health protection in the event of a fire. In addition, users of halogen-free solutions benefit from easier disposal at the end of the product life cycle."
Kraiburg TPE has developed new thermoplastic elastomers for highly effective fire protection.
