Synthesis Of An Intumescent Flame Retardant With A Hexafunctional Cyclotriphosphazene Core And Its Application On PP

Polypropylene (PP) is one of the most widely produced and used resin in the world.However, the flammability of PP (LOI is only17) significantly limits its wide application,Much work should be done for non-halogenated flame retarded PP system due to the pressureof environment issues. Intumescent flame retardant (IFR) is environmentally friendly andusually composed of phosphorus, nitrogen and carbon. When heated, IFR can form a swellingchar layer, which can provides a thermal and physical barrier to the underlying material orbulk polymer during combustion. In this thesis, based on molecule design, a novel IFR wassynthesized and applied to PP, the flame-retardant mechanism was studied.The detailed thesis can be divided into two parts as following:In the first part,1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2] octane(PEPA) was synthesized from pentaerythritol and phosphorus oxychloride. Then,hexachlorocyclotriphosphazene (HCCP) was reacted with PEPA to generate six(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2,2,2] octane-4-methyl) cyclotriphosphazene (PEPAP).Furthermore, the routines were optimized, and the structures were characterized by FT-IR and1H NMR. The result of thermal analysis showed that PEPAP had excellent thermal stabilityand char-forming ability, yielding34.0wt%char residue at800oC in nitrogen atmosphere.In the second part, the PEPAP was applied to PP resin and PEPAP/PP composites wereprepared via melt blending method. From the results of LOI and UL94tests, it can be foundthat flame retardant PP material with the suitable content of PEPAP has better flame retardantproperties and a higher fire safety than pure PP. when the content of PEPAP was25%, theLOI value were29.5and the sample could reach the UL-94V-2rating. The thermal behaviorswere investigated by TGA, and the results shows that the flame retardant PP degraded aheadof pure PP under both air and nitrogen atmosphere, but the final residue was much higherthan that of pure PP. In addition, TG-MS-IR studies thermo-oxidative degradation mechanismof the intumescent system, and the addition of PEPAP is found to increase the thermal stability. The char layer after the flame retardant PP burned was studied by SEM, FT-IR.Results showed that the compact char layer was a crucial factor for the flame retardancy of PP.Phosphorus-containing compounds were detected in intumescent char, and they could delaythe oxidation of PP.