Preparation Of Halogen-free Cycltriphosphazene Flame Retardant And Application In Polypropylene

In this paper, the application of phosphazene flame retardant in polypropylene has been studied. Firstly, synthesised halogen-free phosphazene flame retardant by substitution reaction. Then, prepared flame retardant samples and tested they 、performance. Finally, the flame retardant mechanism of phosphazene has been took a briefly discussed.In appropriate conditions, hydroxyl compound and hexachlorocylcotriphosphaze ne would took nucleophilic substitution reaction and got halogen-free phosphazene flame retardant. During the experiment, tetrahydrofuran, dioxane, acetonitrile as the reaction solvent, and compared the effect, we will found acetonitrile as solvent effect is best. Phenol, pentaerythritol(PER), 1-oxo-4-hydroxymehyl-2,6,7-trioxa-1-phosphabicyclo[2,2,2,] octane(PEPA) as raw material, react with hexaphophazene respectivel y, obtained halogen free phosphazene flame retardant hexaphenoxycyclotriphosphaze ne(HPCP), poly(cyclotriphosphazene-co-pentaerythritol)(PCPP), six(1-oxo-2,6,7-trioxa-1-phosphabicyclo[2,2,2] octane-4-methyl) cyclotriphosphazene(PEPA P). Fourier transform infrared spectroscopy, 1H-NMR were employed to characterize the products and thermogravimetric analysis, scanning electronic microscopy were used to investigate its potential as flame retardant. The results show that we succeeds prepared the target product, and the product can be applied as flame retardant in the polymer. What more, PEPAP and PCPP can be used as intumescent flame retardants for its excellent expansion capability.A series of flame retardant PP composites(FR-PP) were prepared via melt blending method. Flame retardant properties and mechanical properties of FR-PP were evaluated through thermogravimetric analysis, UL-94 experiments, limiting oxygen index, charpy impact testing machine and electronic universal testing machine. For 25%HPCP/PP sample, the LOI value is increased to 26.5% and it can pass UL-94 V-0. HPCP/PP composite maintain good mechanical properties. PCPP show the ability to greatly reduce flame spread rate, UL-94 HB could be passed only containing 5% PCPP. But composites mechanical properties will be deteriorated with PCPP added.The decomposition activation energy of FR-PP was calculated by Flynn-WallOzawa method. Compared with pure polypropylene decomposition activation energy, we found that the addition of HPCP can effectively improve the decomposition activation energy of polypropylene. However, the addition of PEPAP and PCPP will reduce the decomposition activation energy of PP composite. These phenomena are correspond with them flame retardant mechanism. FR-PP are heat-treated at different temperatures, and characterized by FTIR. By infrared spectrum analysis, we hypothesized the decomposition process and inferred its flame retardant mechanism. This observation shows that HPCP mainly produced a gas-phase flame-retardant effect in this specimen, and PEPAP, PCPP mainly produced a condensed-phase flame retardant effect.