Construction of flame-retardant and recyclable tung oil-based polyurethane composite foam: A green way to comprehensive utilization

Traditional petroleum-based thermoset polyurethane (PU) foams are inherently limited by their non-recyclability and high flammability. In this study, tung oil (TO) and salicylaldoxime (SA) were used as raw materials to synthesize bio-based polyols (TO-SA) via Friedel-Crafts alkylation. These polyols were then used to produce tung oil-based polyurethane (TPU) foam. The resulting TPU foam, containing phenol-carbamate and oxime-carbamate bonds, demonstrated the ability to be repeatedly hot-pressed into a TPU film. To reduce the flammability of the TPU foam, a multifunctional flame retardant (PTC@FeHP) was prepared by in-situ immobilizing iron phenylphosphinate (FeHP) on the phytic acid activated tung meal-based carbon (PTC). The addition of 15 wt% PTC@FeHP to the TPU foam significantly improved its flame retardancy, achieving a UL-94 V-0 rating and an LOI value of 28.2 vol%. Moreover, the total heat release (THR), total smoke release (TSR), CO production, and CO 2 production were reduced by 58.3 %, 70.3 %, 50.0 %, and 34.4 %, respectively, compared to the virgin TPU foam. Notably, the incorporation of PTC@FeHP didn’t affect the recyclability of the TPU foam, but rather improved the mechanical, flame retardant, and photothermal conversion performance of the TPU film, giving it great potential for photothermal power generation. This study provided a novel strategy for the development of flame-retardant and recyclable bio-based PU foam, emphasizing the comprehensive utilization of forestry resources.