Preparation and performance investigation of high solid content flame retardant waterborne polyurethane

To improve the flame retardancy and solid content of waterborne polyurethane (WPU), AOT, and AOD series of WPU were synthesized and characterized. Carboxylic acid/nonionic composite units were used as hydrophilic groups, and OP550/THPO and OP550/DOPO-HQ combinations were used as flame retardant modifiers, respectively. The results revealed that the flame retardant-modified WPU emulsions still had excellent dispersion, stability, and fluidity. The UL-94 rating of modified WPU could reach V-0, and the AOD series samples had better flame retardancy than the AOT series, where AO 10 D 3 -WPU containing 3% DOPO-HQ had an limiting oxygen index value up to 30.5%. Besides, the peak heat release rate and total heat release of AO 10 D 3 -WPU were respectively decreased by 32% and 34%, compared with the control sample in the conical calorimetric test. The TGA, TG-IR, and SEM-EDS exhibited that the flame retardants functioned in the condensed phase by promoting carbon formation. The tensile strength of AOT series samples was excellent with a range of 15.84–27.47 MPa, while the elongation at break of AOD series samples was relatively high with a distribution of 850.8%–913.11%, which could be selected to suit the needs of different application scenarios.