An eco-friendly intumescent flame retardant with high efficiency and durability for cotton fabric

The eco-friendly flame-retardant I-type ammonium polyphosphate (I-type APP) has poor water solubility and poor durability when applied to textiles, limiting its application in the textile industry. In this study, we resolve I-type APP solubility in water and then improve its durability for cotton fabric. The resolvable APP was grafted onto cotton fabrics by the P–O–C bonds. The limiting oxygen index (LOI) values of the 30% APP-treated cotton fabric was 50.1%; after 50 laundering cycles (LCs), the LOI values still retained 28.5%. No after-flame and after-glow were observed in the vertical burning test. These experimental results imply that the APP-treated cotton fabrics have high flame retardancy and excellent durability. Scanning electron microscopy showed that the surfaces of cotton fabric before and after treatment were similar and no material was deposited on the surface. X-ray diffraction analysis demonstrated that the crystal structures of the APP-treated cotton were almost unaffected. The thermogravimetric (TG) and TG-infrared (IR) analysis indicated that the treated cotton produced phosphoric acid or polyphosphoric acid during thermal decomposition to promote the dehydration and carbonization of cellulose in favor of char form. The results of the microcalorimetry indicated that the total heat release and the peak of the heat release rate of the treated cotton were significantly lower than those of the control cotton. The whiteness indexes, tensile strengths and bending lengths of the APP-treated cotton fabric showed that it still maintained good physical properties.