Bio-based flame retarded thermo-reversible polymer fabricated by lignin and epoxidized soybean oil based on Diels-Alder reaction

A bio-based flame retarded thermo-reversible polymer was fabricated using furan-terminated lignin (FL) and furan-functionalized epoxidized soybean oil (FE) via Diels-Alder reaction. Two kinds of 9,10-Dihydro-9-Oxa-10-Phosphaphenanthrene-10-Oxide (DOPO) based flame retardants, including ESO ring-opening derivative (DE) and furanized reactive flame retardant (DF), were synthesized and incorporated into the networks. The incorporation of FL increased the crosslinking density, and reinforced the as-prepared FL/FE network. However, its rigid macromolecular structure also impaired the self-healing properties of network. The addition of DE and DF both improved the flame retardant properties, and they also exhibited synergistic effect during combustion. The LOI value of 80FE/10FL/5DE/5DF reached 29.3 %, and the UL-94 test also reached V-0 level. Whereas, due to the rigid molecular structure similar to lignin and the increased local cross-linking density, the incorporation of DF deteriorated the self-healing efficiency of network. On the contrary, the specimen with the incorporation of DE exhibited relative high self-healing efficiency due to the existence of hydrogen bonds. Typically, 80FE/10FL/10DE exhibited a high tensile strength (11.91 MPa), while maintained a relative high self-healing efficiency (80.45 %). These properties provide valuable insights for the practical application of bio-based polymers in sustainability and flame-retardant fields, and may have application potential in the packaging field in the future.