Abstract:

Lignin contained abundant carbon atoms in its chemical structure, which could be used as filler in polymer materials to provide carbon source and promote flame retardant in the combustion process of polymer materials. The molecular structure of lignin contained active groups such as aromatic group, phenolic hydroxyl group and alcohol hydroxyl group. A series of lignin-based flame retardants could be obtained by introducing flame retardant elements or groups into the chemical structure of lignin through chemical modification. Starting from the structure of lignin, this paper summarized the domestic and foreign research progress of unmodified lignin, nitrogen and phosphorus modified lignin, and nitrogen and phosphorus modified lignin doped with copper or non-metallic elements like silicon as flame retardants in different polymeric materials, including physical synergistic flame retardant formulations, chemical modification preparation process and the comparison of flame retardancy effect before and after treatment. The flame retardant mechanism of the corresponding flame retardants was analyzed, including the oxygen isolation effect by the released non-combustible gas, the formation of dense non-combustible carbon layer, and the hindering effect on heat transfer. Additionally, the application prospect of lignin-based flame retardants was prospected.

Key words: lignin, fire retardant, polymer, chemical modification, flame retardant mechanism