Synthesis of a novel P-N reactive ammonium phosphate-based flame retardant for durable finishing of cotton fabric

Abstract

Cotton fiber is a very common natural fiber and widely used in many aspects of life, but it is extremely flammable due to its low limiting oxygen index (LOI) of only about 18%. Therefore, it is necessary to impart flame retardancy to cotton fabrics. In this paper, N,N,N′,N′-tetra (2-hydroxypropyl) ethylenediamine (EDTP) was used to synthesize a novel P-N flame retardant (FR-EDTP) by a two-step method. FR-EDTP was then successfully grafted onto cotton fabrics to improve their flame retardancy. The treated cotton fabrics could withstand multiple washing cycles. The structure of the flame retardant was characterized by 1H NMR, 13C NMR, and 31P NMR. The results of FTIR, scanning electron microscopy (SEM) and elemental analysis confirmed that the flame retardant was successfully combined with cotton fabric. SEM and X-ray diffraction (XRD) results showed that the flame retardant only slightly damaged to the structure of cotton fabrics. The LOI and the vertical burning tests intuitively showed that the treated cotton had high flame retardancy and washing resistance. The LOI value of cotton fabric treated with 30 wt% FR-EDTP reached 39.7%, and after 50 laundering cycles (LCs), its LOI value remained at 28.2%. Cotton fabric treated with 20 wt% FR-EDTP could still withstand 30 LCs. The vertical burning test indicated that the treated cotton self-extinguished after being ignited and retained an intact carbon frame after combustion. Thermogravimetric (TG) analysis and cone calorimetry test were used to evaluated the flame retardant property and thermal stability of treated cotton.