Preparation of a synergistic reactive flame retardant based on silicon, phosphorus and nitrogen and its application to cotton fabrics

Abstract

A novel compound containing silicon, phosphorus and nitrogen, named 1-(9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide)-4-(trimethoxysilylmethyl) piperazine (DOPO-PiP-Si), was synthesized as a reactive flame retardant and applied to prepare flame-retardant cotton fabrics. Its structure was characterized by Fourier transform infrared spectra, 1H and 13C nuclear magnetic resonance (1H NMR and 13C NMR), and flame retardancy of treated cotton fabrics was investigated thoroughly using the limited oxygen index (LOI), vertical burning test, thermogravimetric analysis and cone calorimetry test (CONE), respectively. The LOI value of the cotton fabrics treated with DOPO-PiP-Si increased to 27.6% and the char length decreased to 12.2 cm without afterflame and afterglow. From the results of CONE test, the peak heat release rate and total heat release of treated cotton fabrics decreased from 230.8 to 161.1 kW/m2 and from 6.4 to 4.5 MJ/m2, respectively. Besides, the char residue reached 19.1%, which indicated that the treated cotton fabrics had excellent char formation ability and thermal stability. The morphology of char of the treated cotton fabrics was also characterized by scanning electron microscopy, it can be seen from results that the structure of fiber had no shrinkage and a few bubbles were distributed on the surface of fiber, which suggested that the treated cotton fabrics could display gas-phase flame retardant mechanism.