Synthesis of a novel self-intumescent flame retardant with spiro and triazine structure and its performance for polypropylene

Abstract

A novel self-intumescent flame retardant, tris(2-hydrooxyethyl), isocyanurate spirocyclic pentaerythritol bisphosphonate ester (THECP), was synthesized through solution polycondensation by tris(2-hydroxyethyl) isocyanurate and spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride. The product was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis. Results of limiting oxygen index and UL-94 test demonstrated that the THECP effectively improved flame retardancy to polypropylene. Moreover, with the addition of ammonium polyphosphate, limiting oxygen index value increased to 33.9 and passed the UL-94 V-0 rating simultaneously. Their combustion, performance, and thermal properties were evaluated by CONE, thermogravimetric analysis, and thermogravimetric analysis-Fourier transform infrared spectroscopy. The morphology and chemical structure of the residual chars were observed by scanning electron microscopy and Fourier transform infrared spectroscopy. The results illustrated that THECP can greatly increase residual chars and delay the decomposition rate of matrix. THECP and ammonium polyphosphate contributed to fully exerting both gaseous and condensed phase effects.