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

Abstract

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-(NOÁ) 2 at 30 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, 13 C-NMR, EPR, et al. The results indicated that HCO 4À was generated in BAP system, and then further produced ROS ( 1 O 2 , ÁO 2 À and ÁOH) 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.