Penglun Zheng

To overcome the flammability, poor charring, and brittleness of epoxy resin (EP), a flame‐retardant additive, BPD, was synthesized from N‐aminoethylpiperazine, 4‐acetylphenylboronic acid, and DOPO, and then incorporated into EP to obtain EP/BPD composites. With 3 wt% BPD, the LOI increased from 25.7% to 28.3%, and the UL‐94 rating improved from NR to V‐0. At 5 wt% BPD loading, pHRR, THR, SPR, TSR, COP, and CO ₂ P decreased by 39.1%, 10.2%, 42.8%, 74.3%, 30.0%, and 39.3%, respectively, versus pure EP, demonstrating excellent flame retardancy, smoke suppression, and fire safety. Moreover, 1 wt% BPD raised impact strength to 28.79 kJ/m ² (65.9% increase), while tensile (51.98 MPa) and flexural strengths (69.78 MPa) remained nearly unchanged, achieving a synergistic balance of flame retardancy and mechanical toughness.

To address the flammability and brittleness of epoxy resin (EP) while meeting green development demands, we developed SiVD, a lignin‐derived vanillin‐based halogen‐free flexible‐chain flame retardant. At 5 wt% SiVD, modified EP achieved a limiting oxygen index of 30.1% and UL‐94 V‐0 rating. Cone calorimetry revealed 24.4% and 28.3% reductions in peak heat release rate and total heat release versus pure EP, along with markedly suppressed smoke production, demonstrating excellent flame retardancy and smoke suppression. The flexible segments of SiVD effectively alleviate EP's inherent brittleness. Even at an ultra‐low 1 wt% loading, impact strength reached 60.31 kJ/m ² (247.6% higher than pure EP), while tensile and flexural strengths remained comparable, truly realizing synergistic enhancement of flame retardancy and toughness. Mechanistic studies show a dual‐mode flame‐retardant action: in the condensed phase, SiVD promotes a dense protective char layer; in the gas phase, it quenches free radicals and releases inert diluents. For toughening, its flexible moieties absorb impact energy, and excellent interfacial compatibility with EP mitigates mechanical deterioration typically caused by conventional flame retardants. This work offers a novel strategy for developing eco‐friendly, high‐performance flame‐retardant EP materials.

To mitigate the limitations of red phosphorus (RP) flame retardants, such as pronounced hygroscopicity and oxidation susceptibility, a high‐efficiency flame retardant (HLE) was synthesized via hydrolytic microencapsulation and incorporated into an epoxy resin (EP) matrix. It was found that the composite with 7 wt% HLE (EP/7‐HLE) exhibited a limiting oxygen index of 34.4% and attained a UL‐94 V‐0 rating, with a self‐extinguishing time of 3 s. Cone calorimetry tests revealed a 43.2% reduction in peak heat release rate (PHRR = 768 kW/m ² ) and a 33.1% decrease in total heat release (THR = 83 MJ/m ² ) compared to pure EP. Thermogravimetric analysis confirmed enhanced thermal stability with 23.2% char residue at 800°C, while dynamic mechanical analysis indicated an elevated glass transition temperature of 187°C. Microstructural characterization (SEM/Raman spectroscopy) demonstrated that HLE promotes the formation of a compact, highly graphitized char layer (I _D /I _G = 1.99), effectively insulating against heat and oxygen transfer. TG‐IR (Thermogravimetric Analysis coupled with Fourier Transform Infrared Spectroscopy) pyrolysis confirmed the significant suppression of harmful gas emissions, including CO ₂ and aromatic compounds, by the HLE/EP system. The flame‐retardant mechanism is attributed to a synergistic dual‐phase effect involving gas‐phase actions (radical quenching and gas dilution) and condensed‐phase actions (phosphorus‐catalyzed char formation and physical barrier effects).

Compared with traditional flame retardants, highly carbonaceous flame retardants show comprehensive advantages in terms of efficient flame retardancy and multi‐scenario applicability. In order to address the compatibility and carbon formation effect of ammonium polyphosphate (APP) in epoxy resins (EPs), an efficient P‐N‐Si synergistic flame retardant SCAP was synthesized in this study by a hydrolysis‐covering process based on the presence of Si‐bearing Schiff bases in flame retardants. Added to EP, SCAP/EP can achieve excellent fire safety and shows good self‐extinguishing off‐fire capability and inhibition of heat and smoke release during testing. The material's PHRR decreased from 1089 kW/m² of pure EP to 796 kW/m² with the addition of 7 wt% of SCAP, according to the data, and it was rated V‐0 in the UL‐94 rating. In addition, EP's mechanical, tensile, and flexural strengths were increased by adding SCAP. Mechanistic analysis revealed that when exposed to heat, the Schiff base promoted a high degree of aromatization of the carbon skeleton, producing a high‐quality carbon layer that had a good flame‐retarding action. Furthermore, APP and other gas‐phase flame‐retardant components were crucial to gas‐phase flame retardancy.