What materials are used for fire-resistant and flame-retardant cable trays

Cable trays use flame-retardant materials like PVC, LSZH, and XLPE, and fire-resistant materials such as mica tape, ceramicized silicone, and magnesium oxide to prevent fire spread and maintain circuit integrity.

Flame-Retardant Materials

Flame-retardant cables are designed to limit flame propagation and self-extinguish after exposure to fire. Their insulation and sheath typically incorporate flame-retardant additives, which can be halogen-based or halogen-free. These additives decompose under heat, releasing inert gases like carbon dioxide and water vapor, which dilute oxygen and isolate the flame from the cable material. A carbonized layer forms on the surface, blocking heat transfer and enhancing self-extinguishing properties. Common base materials include:

• PVC (Polyvinyl Chloride): Cost-effective, stable flame-retardant performance, but releases toxic gases like hydrogen chloride when burned.
• LSZH (Low-Smoke, Halogen-Free): Produces low smoke and no toxic gases, ideal for high-density areas such as hospitals, subways, and high-rise buildings.
• Flame-retardant XLPE (Cross-Linked Polyethylene): Offers good thermal and mechanical properties while limiting flame spread. Structurally, flame-retardant cables often use a tight sheath with flame-retardant fillers, and some multi-core designs include oxygen barriers to prevent fire propagation between conductors. These cables are effective at slowing fire spread but cannot maintain electrical operation under prolonged fire exposure ( ).

Fire-Resistant Materials

Fire-resistant cables, also called circuit integrity or fire survival cables, are designed to maintain electrical conductivity during fire conditions, ensuring critical systems like alarms, emergency lighting, and smoke exhaust continue functioning. Key materials include:

• Mica Tape: Non-flammable, high melting point (>1200°C), forms a ceramicized shell around conductors to insulate against heat.
• Ceramicized Silicone Rubber: Provides high-temperature resistance and flexibility.
• Magnesium Oxide Mineral Insulation: Offers excellent thermal stability and fire resistance. These materials allow cables to withstand temperatures of 800–1000°C for durations of 30, 60, or 90 minutes while preserving conductor insulation, which is essential for safety-critical applications ( ).

Summary

• Flame-retardant cables: Focus on preventing fire spread, using PVC, LSZH, or XLPE with flame-retardant additives.
• Fire-resistant cables: Focus on maintaining circuit integrity, using mica tape, ceramicized silicone, or magnesium oxide insulation. Choosing the appropriate material depends on the application, fire safety requirements, and regulatory standards. Flame-retardant cables are suitable for general fire containment, while fire-resistant cables are essential for emergency systems and critical infrastructure ( ).