Design of Hierarchical NiCo-LDH@PZS Hollow Dodecahedron Architecture and Application in High-Performance Epoxy Resin with Excellent Fire Safety

Developing advanced performance epoxy (EP) resin with low flammability and light smoke has been an increasing focus of its research. Especially, it is crucial to reduce the emission of smoke and toxic gases generated during the burning of EP, so that it meets the green and safe industrial requirement. Therefore, a 3D NiCo-LDH@PZS hollow dodecahedral structure was designed and synthesized by using the ZIF-67 as both the precursor and an in situ sacrificial template and the amino group-containing polyphosphazene (PZS) as interfacial compatibilizer and flame retardant cooperative. The release behaviors of heat, smoke, and poisonous gases were carefully investigated. More precisely, the EP/NiCo-LDH@PZS4.0 is endowed with a decrease of 30.9% and 11.2% of the peak heat release rate and the total heat release, respectively. The emissions of smoke and poisonous gases including nitric oxides, aromatic compounds, carbonyl compounds, oxycarbide, and hydrocarbons are much less as well. Especially, the maximum release concentrations of HCN of EP/NiCo-LDH4.0 are reduced by 87.8%. With regard to styrene, methane, and ethane, the maximum release concentrations of EP/NiCo-LDH@PZS4.0 are reduced by 85.9%, 90.6%, and 93.1%, respectively. The total yield of CO and CO₂ and the consumption of O₂ of EP/NiCo-LDH@PZS4.0 are also reduced by 64.5%, 32.4%, and 33.6%. The fractional effective dose, an index of toxicity smoke, of EP/NiCo-LDH@PZS4.0 is reduced by 20.4%. The DMA tests were performed to study the mechanical properties of EP composites, and the storage modulus and Tg of EP composites are increased with the incorporation of NiCo-LDH@PZS. The possible mechanism of flame retardant was proposed based on the analysis of the condensed and gas phases of EP composites.