Synergistically Enhanced Flame Retardancy and Mechanical Strength of Rubber Compounds via Sepiolite-Supported Layered Double Hydroxide

Styrene–butadiene rubber (SBR) is widely used in conveyor belts and cable sheaths, but readily releases combustible volatiles when exposed to heat or flame. Flame retardants must therefore improve fire safety without compromising mechanical properties, a challenge often caused by high loadings or poor dispersion. Herein, an inorganic nanohybrid flame retardant (LDH@SEP) was prepared by in situ growth of Ni–Fe layered double hydroxide (LDH) on sepiolite nanorods (SEP) and subsequently incorporated into SBR. The one-dimensional SEP scaffold suppressed the restacking of LDH nanosheets and promoted their dispersion, whereas the sepiolite framework supported char formation and Ni/Fe species catalyzed carbonization. The SBR/LDH@SEP composite achieved a limiting oxygen index (LOI) of 21.8%, a UL-94 V-1 rating, and a tensile strength of approximately 11.2 MPa. SEM, Raman spectroscopy, and TG-FTIR analyses indicated that LDH@SEP promoted a denser and more continuous protective char layer and reduced the release of combustible pyrolysis volatiles. This halogen-free nanohybrid provides a route to SBR composites with improved flame retardancy and mechanical strength. Highlights LDH@SEP was prepared by in situ growth of Ni–Fe LDH on SEP. SBR/LDH@SEP achieves an LOI of 21.8% and a UL-94 V-1 rating. LDH@SEP increases tensile strength while maintaining high elongation at break. A dense char layer and reduced volatile release improve fire safety.