A novel synergistic flame retardant containing phosphonate groups and diboraspiro rings for cotton fabrics

A novel B/P/N synergistic flame retardant, Tetraethyl diboraspiro triazinyl bis phosphonate (TDBTZP), was synthesized and applied to fabricate flame retardant cotton fabrics. The surface morphology of flame-retardant cotton fabrics was analyzed by a scanning electron microscope (SEM). The limiting oxygen index (LOI) experiment and the vertical flammability test (VFT) demonstrated that when the weight gain (WG) of cotton fabric was 28.5%, the length of the residue was 64 mm, and the maximum LOI value reached 35.2%, which remained at 27.1% after 20 laundering cycles (LCs). The TG experiment demonstrated that the treated cotton fabric has good thermal stability, and the char residue rate can reach up to 39.1% in nitrogen atmosphere. The cone calorimetry test demonstrated that when the WG of cotton fabric was 18.3%, the TSP of the treated cotton fabric decreased by 57%. The flame-retardant mechanism analysis demonstrated that TDBTZP achieved the flame retardant effect through releasing incombustible gas and promotes the carbonization of cotton fabrics, indicating that it has the flame retardant mechanism of both gas phase and condensed phase.