A novel ceramifiable additive based on secondary modification of layered double hydroxides imparts enhanced mechanical properties, thermal insulation and low-temperature sintering performance to ethylene vinyl acetate copolymer composites

Developing polyolefin composites with superior flame retardancy, thermal insulation, and ceramicability is crucial for expanding their applications. Inspired by the natural tuff formation from volcanic ash, a novel flame-retardant ceramifiable additive was designed for polyolefin matrices, which was composed of secondary modified layered double hydroxides (LDHs), ammonium polyphosphate (APP) and wollastonite (WS). During combustion, the synergistic interaction between LDHs and APP promoted the formation of a protective char barrier. Simultaneously, the metal oxide residues derived from LDHs reacted with WS and phosphates from APP to generate a dense, coherent ceramic layer. The optimized composite achieved self-extinguishing without flaming drips (V-0 rate) and a limiting oxygen index of 28 %. Compared to the control sample, its peak heat release rate and total smoke release were significantly reduced by 48.01 % and 71.47 %, respectively. Moreover, the sintered residue optimized sample at 1000 °C exhibited a high flexural strength of 24.46 MPa. This work provides an effective strategy for fabricating efficient and sustainable fireproof materials and broadens the utilization of mineral fillers in high-performance ceramifiable polymer composites.