Preparation and performance of waterborne polyurethane coatings based on the synergistic flame retardant of ferrocene,phosphorus and nitrogen

A synergistic reactive flame-retardant polyol (AFeDH) containing ferrocene, phosphorus, and nitrogen elements was synthesized from ferro-formaldehyde, 5-amino-1,3, 4-thiadiazole-2-mercaptan, 9,10-dihydro-9-oxa-10-phos-phaphenanthrene-10-oxide and hydroxyl terminated polybutadiene acrylonitrile, and then applied for flame retarding waterborne polyurethane (WPU). The chemical structures of intermediates and final products were well characterized to confirm the successful preparation of ternary P-N-Fe flame retardant. The effects of incorporated AFeDH on thermal stability, flame retardancy and mechanical properties of AFeDH/WPU films were systematically studied. The results indicated that LOI value increased with the increase amount of AFeDH, while the value then decreased as the loading content above 6 wt%. This increase in flame retardancy results from the competition between the catalytic degradation of iron and the catalytic carbonization. Benefiting from the good synergistic effects among each element of AFeDH, the WPU/AFeDH films perform the decreased heat release and smoke production. Moreover, the flame retardant films also show the enhanced tensile strength of 33.8 MPa and elongation at break of 763.3%. Therefore, this novel halogen-free flame retardant shows an excellent synergistic effect among P, N, and Fe elements, which has a great potential in the application of flame retardant WPU.