A novel, green strategy based on bicarbonate activated hydrogen peroxide system for triazine hindered amines nitroxide radicalization for halogen-free flame retardants

The triazine hindered amine (THA) nitroxide radicals are important to the preparation of halogen-free flame retardants, but the traditional methods using peracetic acid was limited in further sustainable development in industry. In this work, the bicarbonate-activated hydrogen peroxide system with ethyl acetate as the solvent (BAP-EA system) was firstly employed in TH-7 nitroxide radicalization, which exhibited excellent performance with 99% yield of TH-7-(NO center dot)(2) at 30 degrees C. To further explore the mechanism, the bicarbonate transformation, the generation of reactive oxygen species (ROS), and the effect of ROS were explored by LC-MS, C-13-NMR, EPR, et al. The results indicated that HCO4- was generated in BAP system, and then further produced ROS (O-1(2), center dot O-2(-) and center dot OH) to participate in the radicalization. ROS also exhibits synergistic effects in BAP-EA system, and further enhanced the reactivity of ROS in TH-7 nitroxide radicalization. Moreover, in the flame retardancy test, NOR 116 synthesized in BAP-EA system displayed excellent flame retardant synergy with aluminum hypophosphite (AH) in polypropylene (PP). This work provides a novel insight in green process of THA nitroxide radicalization for halogen-free flame retardants.