With increasing fire safety requirements in electronics, electrical appliances, and construction, the flame retardancy of silicone rubber has become a research hotspot. Through the development of halogen-free flame retardant systems and synergistic technologies, the flame retardancy rating of silicone rubber can be upgraded to UL94 V-0 while maintaining excellent mechanical properties.

1. Phosphorus-Nitrogen Synergistic Flame Retardant System

Ammonium polyphosphate (APP) and melamine cyanurate (MCA) are compounded and added to silicone rubber to form an intumescent flame retardant coating. At a total filler content of 20 wt%, the limiting oxygen index (LOI) of silicone rubber increases from 21% to 32%, and it passes the vertical burning test at V-0 level. Thermogravimetric analysis shows that the flame retardants decompose at 300-400°C to form a carbon layer, effectively blocking heat transfer.

2. Layered Double Hydroxide (LDH) Nano-Composite Flame Retardancy

Mg-Al LDH nanosheets are prepared via coprecipitation, modified with silane coupling agents, and dispersed in silicone rubber. At 5 wt% LDH content, the peak heat release rate (pHRR) of the composite decreases from 800 kW/m² to 450 kW/m², while tensile strength remains above 6 MPa. This nano-composite technology balances flame retardancy and mechanical properties.

3. Molecular Design of Reactive Flame Retardants

Phosphorus-containing siloxane monomers (e.g., DOPO-Si) are synthesized and incorporated into the silicone rubber backbone via copolymerization. These reactive flame retardants decompose at 450°C, imparting permanent flame retardancy. Experiments show that silicone rubber with 10 mol% DOPO-Si achieves an LOI of 30% and no dripping during combustion, making it suitable for wire and cable insulation.


High Temperature Resistance Silicone Rubber