Synthesis Of Phosphazene Derivatives And Their Flame-retardant Study In Epoxy Resin

Phosphazene compounds are a new family of biodegradable polymers contained alternating phosphorus and nitrogen in their skeleton and based on the repeating unit of -N=P(R2)-, where R can be halogen, pseudohalogen, amino, azido, or a wide variety of organic groups such as alkoxy, aryloxy, alkylamino, arylamino, alkyl, or aryl. Mixed substitution is also possible under proper control. Epoxy resin is one of the most widely used polymers resin. Epoxy resin is inflammable, so it is important to develop modified epoxy resin. In this article, two phosphazene derivatives were prepared and applied in epoxy resin, and the pyrolysis process are studied.Firstly, hexakis (phenoxy) cyclotriphosphazene (HPCP) and hexakis (aniline) cyclotriphosphazene (HACP) were prepared by phenoxy and aniline as reactants reacted with hexachlorocyclotriphosphazene, respectively. Their structure and purity were characterizated by fourier transform infrared spectrophotometry (FTIR), melting point testing and nuclear magnectic resonance (NMR).Secondly, flame retardant epoxy resin was prepared by adding HPCP and HACP quantificationally. The flame retardant properties and pyrolysis process were studied by limited oxygen index (LOI), thermogravimetric analysis (TGA), TG-MS analyzer and scanning electron microscope (SEM). Also, the possible retardant mechanism was provided. The results indicated that HPCP and HACP had a good thermal stability. When the additive amount of HACP and HACP reached to 10 phr, the LOI of flame retardant epoxy resin reached to 27% and 25.5%, respectively. HPCP had a diversified flame retardant mechanism related to gas-phase and and solid-phase and HACP had a solid-phase flame retardant mechanism.Thirdly, epoxy resin was modified by classical intumescent flame retardant compounded system of ammonium polyphosphate (APP) and pentaerythritol (PER) to prepare the flame retardant epoxy resin and its flame retardant properties and pyrolysis process was compared with the epoxy resin modified by HPCP and HACP by the method of limited oxygen index (LOI), thermogravimetric analysis (TGA), TG-FTIR analyzer, scanning electron microscope (SEM) and FTIR of residual products. The results indicated that HPCP was the most effective flame retardant among the three kinds of flame retardant, and the flame retardant mechanism of HACP dominated by solid phase, which was similar to APP/PER.