Synthesis and Flame Retardant Behavior of Phosphorous‐ and Nitrogen‐Containing Copolymer and Its Application in Polypropylene

Abstract In this study, a 4‐(hydroxymethyl)‐2,6,7‐trioxa‐1‐phosphabicyclo2.2.2octane 1‐oxide (PEPA)‐functionalized acrylate monomer, PEPAA, is designed and utilized for the synthesis of macromolecular flame retardants poly(PEPAA‐ co ‐AM) with varying PEPAA/AM ratio through copolymerization with acrylamide (AM). The poly(PEPAA‐ co ‐AM) is then incorporated into polypropylene (PP) to prepare PP/poly(PEPAA‐ co ‐AM) composites. The flame retardant effect of poly(PEPAA‐ co ‐AM) on PP is investigated using cone calorimetric test (CCT), and compared with that of PEPAA homopolymer (P‐PEPAA), AM homopolymer (PAM), and blends of P‐PEPAA/PAM. The results demonstrate that, in comparison with P‐PEPAA, PAM, and blends of P‐PEPAA/PAM, the incorporation of poly(PEPAA‐ co ‐AM) significantly enhances the flame retardancy of PP. Notably, the best flame retardancy is achieved when the ratio of PEPAA/AM copolymerization in poly(PEPAA‐ co ‐AM) is 2/8. The morphology and composition of residual chars from combustion are analyzed using SEM‐EDS while the residual graphitization degree is examined through Raman spectroscopy. Additionally, TG‐FTIR‐MS is utilized to investigate the pyrolysis products in gas phase during thermal decomposition of poly(PEPAA‐ co ‐AM). Based on these experimental results, a flame retardant mechanism for poly(PEPAA‐ co ‐AM) is proposed. The PP/poly(PEPAA‐ co ‐AM) composites not only retain the excellent processing properties of pure PP but also exhibit enhanced mechanical properties.