The synergistic effect of biphenyl structure and N element in flame retardant and high value-added recycling of bio-based epoxy resin

Recently, growing concerns about climate change and environmental protection have increased interested in sustainable development of polymer materials. Here, ester-containing bio-based epoxy precursor was prepared, and was cured by 4, 4'-diaminodiphenylmethane (DDM). With the increase of DDM addition, the flame-retardant grade of the resins improved from V-1 to the highest V-0 in the vertical-burning tests. The results indicate that the increased N content was combined with biphenyl radicals and gradually formed thermally stable, nitrogen-rich char to insulate the matrix and improve flame retardancy after cyclization, rearrangement, and dehydrogenation process. Besides, considering the carbon formation mechanism, it was utilized as a potential precursor to prepare N, O dual-doped carbon by using KOH activation and pyrolysis method. The obtained porous carbons possess high CO2 adsorption performance (9.0 mmol g(-1), 273 K), high CO2/N-2 selectivity and good regenerability. Hence, this simple strategy offers an effective, durable, and environmentally friendly solution to increase the fire safety of epoxy resin, and also paves a way to close the loop from green synthesis to high value waste utilization of thermoset resin.