Study On The Sythesis Of Melamine Phosphonic Acid Saltsand Their Flame Retardant Applications On Polyolefin

Melamine phosphonic acid salts are related to phosphorus-nitrogen containing flameretardants, which are the most common parts of intumescent flame retardants. They have theadvantages of free-halogen, good compatibility with polymers, good thermal stability andexcellent flame retardancy. Furthermore, because of being environmentally friendly, they accordwith the tidal current of flame retardants.In this study, two novel phosphorus-nitrogen containing intumescent flameretardants—melaminium hydroxy ethylidene diphosphonate(MHEDP) and melaminenitrilotrimethylene triphosphonic acid(MATMP) were synthesized by the reaction ofhydroxyethylidene-1,1-diphosphonic acid(HEDP) and nitrilotrimethylene triphosphonicacid(ATMP) with melamine(MEL) respectively. Meanwhile, the molecular structures of targetproducts were determined by elemental analysis, FTIR and1H-NMR, and the thermal propertywas investigated by means of TGA. The results indicated that the structures of MHEDP andMATMP meet the expected requirements. To improve the thermal property of MATMP, explorethe appropriate heat treatment condition for MATMP. After heat treatment, the thermal propertyand residual quality of MATMP were both increased.The applications of the flame retardants combined with treated MATMP, melaminephosphate(MP), calcium hypophosphite(CaHP) and hydroxyapatite(HAP) were investigated inLDPE resin. Apply MHEDP, melamine phosphate(MP), melamine cyanurate(MCA), melaminephosphate(MP) and calcium hypophosphite(CaHP) to PP resin. Flame retardancy, thermalproperties and mechanical properties of flame retardant LDPE and PP by above mentionedcompounding system were investigated by LOI experiments, TG and mechanical test,respectively. The results showed that, PP, LDPE with flame retardants had better thermalproperties and flame retardancy. However, for mechanical properties, flame retardants hadnegative effects on LDPE and PP. The LOI of flame retardant LDPE and PP increased slightly,which still can’t meet the requirements of flame retardant materials. Optimize the formula withMHEDP, ammonium polyphosphate(APP) and melamine phosphate(MP) applied in PP resin. Theresults indicated that the compound of MHEDP, APP and MP had a higher flame-retardantefficiency and better mechanical performance.12%MHEDP,12%APP,6%MP added to PP couldachieve UL94V-0rating (3.2mm), and the LOI was35%, while the mechanical properties werewell maintained．The flame retardant mechanism of MHEDP/APP/MP synergistic system on PP and effects on different synergistic PP systems was investigated by Py-GC-MS analysis, CONE andSEM. The cone results showed that compared to PP, the heat release rate(HRR), total heatrelease(THR), smoke release rate(SPR), total smoke release(TSR) and mass loss ofMHEDP/APP/MP synergistic system and MHEDP/MCA/HAP system have decreased, whichsuggested these flame retardants have positive effects on PP. And MHEDP/APP/MP synergisticsystem is better than MHEDP/MCA/HAP system. The Py-GC-MS analysis results showed that thepyrolysis gas-phase products of MHEDP/APP/MP synergistic system did not includephosphorus-containing compound, certain correlation existed between the flame retardancy andthe morphology of char. The mechanisms of MHEDP/APP/MP synergistic system on PP is mainlya kind of condensed phase mechanism.