Hyperbranched polyamide-amine based phosphorous-containing flame retardant for simultaneous flame retardancy and high performance of polypropylene

Currently, the promotion of flame retardancy is facing apparent decrease of mechanical properties for polyolefin, leading to an unresolved contradiction in this field. In this work, novel hyperbranched polyamide-amine based phosphorous-containing flame retardant PPAM-AT was designed to fabricate flame-retarded polypropylene (PP). Interestedly, when the flame retardancy of PP was greatly improved after incorporation of PPAM-AT, mechanical properties of flame-retarded PP were barely damaged compared with corresponding properties of neat PP. At 15% PPAM-AT, the limiting oxygen index (LOI) of PP/PPAM-AT15 reached 30% and the highest V-0 grade was achieved in the burning test; the peak of heat release rate (PHRR) and fire growth rate of PP/PPAM-AT15 were decreased by 83.8% and 60.7% in comparison with corresponding values of neat PP. Meanwhile, tensile strength and elongation at break for PP/PPAM-AT15 maintained at 46.9 MPa and 551.3%, respectively, keeping at a comparative level with that of PP. Analysis on flame-retardant mechanism confirmed that typical intumescent flame retardation played a vital role for the excellent fire safety of PP/PPAM-AT. The reason for excellent mechanical properties of flame-retarded PP/PPAM-AT is ascribed to the multiple factors such as the change in the crystallization of PP, excellent energy-dissipating ability of PPAM-AT, and so on. This work demonstrated that hyperbranched polyamide-amine based phosphorous-containing flame retardant with unique chemical structure may achieve simultaneous flame retardancy and high performance of polypropylene, which opens a new pathway to solve the contradiction between flame retardancy and high performance of polyolefin.