A phosphazene compound multipurpose application -Composite material precursor and reactive flame retardant for epoxy resin materials

Cyclotriphosphazene containing the epoxy group hexaglycidyl cyclotriphosphazene (HGCP) was synthesized in one step. The reaction was a nucleophilic substitution of cyclophosphazene chlorine by the epoxy function of 2,3-Epoxy-1-propanol in presence of triethylamine. The purified compound of the reaction was characterized by FTIR, 31P, 1H, and 13C -NMR nuclear magnetic resonance spectroscopy. This reactive monomer that is inherently flamed retarding contain P and N, can be used on their own as composite material precursor or added to current bulk commercial polymer diglycidylether of bisphenol A (DGEBA) to enhance flame retardancy. The thermal stability and flame retardancy of HGCP thermoset with MDA curing agent and its blend as flame retardant with DGEBA were checked by thermal gravimetric analysis coupled with infrared spectoscopy and the UL-94 vertical test. The correlation between these properties (thermal stability and flame retardancy) and the HGCP contents (phosphorus content) were discussed. The results show that HGCP as composite material precursor lead a good material with thermal stability at elevated temperature compared with DGEBA thermoset with MDA curing agent. HGCP as flame retardant presents a good dispersion in DGEBA, and the blend thermoset with 4,4ʹ-methylene-dianiline (MDA) curing agent leads to a significant improvement of the thermal stability at elevated temperature with higher char yields compared with pure DGEBA thermoset with the same curing agent. HGCP acts with an intumescent char-forming and gas action by CO2 gas emission which its act to dilute the combustible gas. Improvement has also been observed in the fire behaviour of blend.