Synthesis and evaluation of an eco-friendly and durable flame-retardant cotton fabrics based on a high-phosphorous-content

[Display omitted] •ADPHPA was prepared by a two-step, solvent-free method with formaldehyde-free and halogen-free.•ADPHPA can react with the biomolecule of cotton fiber to form POC covalent bonds due to active group -PO(O-NH4+)2.•The decomposition process of TCF was changed compared with CCF, while its combustion efficiency was also reduced.•TCF achieved excellent flame retardancy and washability according to AATCC 61-2013 3A standard. Cotton fabrics are extremely flammable. Therefore, ammonium salt of dipentaerythritol hexaphosphoric acid (ADPHPA), a novel reactive phosphorus flame retardant without halogen and formaldehyde, was synthesized by solvent-free synthesis method. Surface chemical graft modification was chosen to introduce flame retardant, imparting its flame retardancy and washability. SEM indicated that ADPHPA entered the interior of cotton fiber, which was grafted with OH of control cotton fabrics (CCF) by forming POC covalent bonds to obtain treated cotton fabrics (TCF). There were no apparent differences in the fiber morphology and crystal structure after treatment according to SEM and XRD analysis. TG analysis demonstrated that the decomposition process of TCF was changed compared with CCF, while lower heat release rate and total heat release of TCF indicated its combustion efficiency was also reduced based on cone calorimetry test. Meanwhile, in the durability test, TCF had undergone 50 laundering cycles (LCs) in accordance with AATCC-61-2013 3A standard and had a short vertical combustion charcoal length, which were able to be regard as durable flame-retardant fabrics. The mechanical properties of TCF decreased to a degree, but did not affect the actual use of cotton fabrics. Taken as a whole, ADPHPA has research significance and development potential as a durable phosphorus-based flame retardant.