Synthesis and Characterization of High‐Performance Lignin Modified Phenolic Foam

Phenolic foams (PFs) play a crucial role in mine sealing due to fire resistance, high thermal insulation efficiency, and chemical corrosion resistance. However, phenol, the primary raw material, is derived from fossil sources. To address this challenge, phenol is partially replaced with renewable lignin to synthesize an environment‐friendly lignin‐modified phenolic foam (LPF). LPF samples with substitution ratios of 10, 15, 20, 25, and 30 wt% were prepared to compare with pure PF. The results showed that lignin substitution significantly enhances the compressive strength, pulverization resistance, and flame retardancy of the foams. Among all formulas, 20LPF exhibits the most balanced performance, with compressive strength improved by 273% compared to that of the PF, a compact and uniform cell structure, and only a moderate increase in water absorption. However, higher substitution ratios (≥ 25%) lead to markedly increased water absorption and potential long‐term stability concerns, suggesting the need for further optimization.