A novel P–N-based flame retardant with multi-reactive groups for treatment of cotton fabrics

Abstract A novel P–N based, flame retardant ammonium salt of pentaethylenehexamine octa (methylene-phosphoric acid) (APHOMPA) was synthesized in this study. The structure of the prepared material flame retardant contains eight reactive ammonium phosphorus groups and was characterized by 1 H NMR, 13 C NMR, 31 P NMR, and (Fourier-transform infrared) FT-IR. The results showed that cotton fabrics finished with this flame retardant exhibited excellent flame retardancy and durability. The cotton fabrics finished with 30% APHOMPA solution had limiting oxygen index value 40.5%, and maintained 28.8% even after 50 laundering cycles. The FT-IR results showed that APHOMPA could be grafted on cellulose through P–O–C covalent bond. Vertical flammability, cone calorimetry, thermogravimetric (TG), and TG-IR results revealed the excellent flame retardancy of the finished cotton fabrics and suggested that the flame retardant mechanism of APHOMPA is a condensed phase process. Scanning electron microscopy results suggested the flame retardant entered the inner space of the cotton fabrics, and the X-ray diffraction results showed slight changes to the cotton crystal structure in the finishing process. The breaking strength, softness, and whiteness of finished cotton fabrics were sufficient, suggesting this retardant can be used to prepare treated cotton for multiple applications. Graphic abstract