Study On The Synthesis Of Pentaerythritol-based Flame Retardants Andtheir Application In Flame Retardant Polyolefin

With its high carbon content of 44.1%, pentaerythritol was often used as char-forming agent in compounding flame retardants. Meanwhile, it has four reactive hydroxyl groups reacting with certain compounds, which often used as a reaction intermediate in synthesis of other macromolecular flame retardants. From above, we can see that pentaerythritol has broad prospects for development in the field of synthesis of flame retardants.In this study, two pentaerythritol-based flame retardants were successfully synthesized through new processes and new routes, which are tribromoneopentyl alcohol(TBNPA) and 2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane,3,9-dimethyl-,3,9-dioxide(DMDP).In this new route, TBNPA was synthesized by pentaerythritol and phosphorus tribromide. Through nucleophilic substitution of phosphorus tribromideand synthesizing with pentaerythritol, we got tribromoneopentyl alcohol ester. Then we got our final production TBNPA by ester exchange between tribromoneopentyl alcohol ester and methyl alcohol. The yield of this new route in laboratory is 95%, which was conducted pilot in Shangdong Unibron Corp Pte Ltd with its yield up to 90%, which means it has good prospects in industrial application, now they are magnified in production. The molecular structures of the two products was determined by fourier transform infrared spectroscopy(FTIR), elemental analysis(EA) and 1H-nuclear magnetic resonance, 13C-nuclear magnetic resonance(NMR), the thermal properties were investigated by means of differential scanning calorimetry(DSC) and thermogravimetric analysis(TG). Meanwhile, with the Al Cl3 as the transesterification catalysts of anhydrous, DMDP was synthesized by ester exchange between dimethyl methylphosphonate and pentaerythritolin this new process. FTIR, gas chromatography-mass spectrometer(GC-MS) and TG were used to test its structure, constituentsand thermal property, respectively. The results show that the synthesized products consist of DMDP and some by-products, with low purity of DMDP of 37%. The reason of low purity of DMDP maybe was that ester exchange is a complex reaction following various by-productions.In this research, we also preliminary evaluated Tris(2,2-dibromomethyl-3-bromopropyl phosphate application in HDPE as flame retardant, that is an important derivative of TBNPA. Meanwhile, TTBNP and Sb2O3 were added into high density polyethylene(HDPE), while using decabromodiphenylethane(DBDPE) and Sb2O3 compounded to HDPE as a comparative sample. DMDP was also compounded with melamine hypophosphite(MHP) and melamine cyanuric acid(MCA) to ethylene-vinyl acetate copolymer(EVA).Flame retardancy, thermal properties and mechanical properties of flame retardant HDPE and EVA by above mentioned compounding systems were investigated by LOI experiments, TG and mechanical test, respectively.The results show that the LOI of flame retardant HDPE compounding systems was increasing with the increase of flame retardant contents, while the maximum one is 27.5%. We also learned that this flame retardant HDPE compounding system(sample 4) would possess a flame retardant grade of UL94 V-2, only when the addition of the flame retardant is up to 20.8%. The best flame retardant grade of this flame retardant HDPE compounding system is just UL94 V-2: due to brominated flame retardant was worked in gas phase, it can not promote HDPE to charring with the creation of droplets, which will ignite degreasing cotton effecting flame retardant grades. The mechanical properties test results of flame retardant HDPE compounding systems verify that the brominated flame retardant has less effect on the mechanical properties of flame retardant materials, whose tensile strength and impact strength almost has little change, otherwise, the elongation at break was increasing, the largest increase is 126%.The results of flame retardant EVA compounding systems also suggest the LOI was increasing with the increase of DMDP and MCA within the highest LOI of 27.1%.Only sample 6 with compositions as follow: DMDP 3wt%; MHP 9wt%; MCA 28wt%, EVA 60wt%, possessed the flame retardant grade of UL94 V-0,which indicated that this compound flame retardant system in this formula had a superior flame retardant effect on EVA. The mechanical properties test results of flame retardant EVA shows that the addition of this kind of compounding flame retardant has low influence on the elongation at break and impact strength of EVA, but a certain influence on the tensile strength.