A novel guanidine ammonium phosphate for preparation of a reactive durable flame retardant for cotton fabric

A novel reactive N–P flame retardant ammonium salt of guanidine acetate tetramethylenephosphonic acid (AGATMPA) with good solubility was synthesized under mild conditions. AGATMPA was combined with cotton cellulose through P–O–C and C–O–C covalent bonds. The molecular structure of AGATMPA was characterized by ¹H NMR, ¹³C NMR, and ³¹P NMR. The control cotton and treated cotton were characterized by FT-IR, SEM, and EDX to verify that the flame retardant was successfully grafted onto the cotton fabric. The LOI and vertical flammability tests indicated that the AGATMPA-treated cotton showed outstanding flame retardance with LOI of 45.5% and durability with LOI of 29.5% after 50 laundering cycles, respectively. TG analysis showed that treated cotton exhibits favorable thermal and thermal oxidation stability, and the carbon residual can reach 42.26% in nitrogen and 12.55% in air at 700 °C. Cone calorimetry suggested that the PHRR and THR values of treated cotton decreased by 95.18% and 70.07%, respectively. TG-IR results revealed that the amount of thermally-degraded volatiles of treated cotton decreased and no new types of toxic gases were produced, compared with control cotton. XRD results showed little change in the crystalline region of the cotton fabric before and after treatment with AGATMPA. The flame retardant finishing process has some effect on the physical properties of cotton fabric while only slightly influencing its application.