Preparation Of A Novel Mono-component Intumescent Flame Retardant And Its Application For Highly Effective Flame Retarded Polyolefin

Polyolefin including polyethylene(PE),ethylene-vinyl acetate copolymer(EVA),ethylene-octene copolymer(POE)and so on were widely used in the fields of electronics and electrical appliances,packaging,automotive,communications,agriculture and construction due to their advantages of environmental friendly,easy processing and chemical resistance.However,the flammability of polyolefin limited their applications in many areas.The intumescent flame retardant(IFR)can effectively improve the flame retardancy of polyolefins.However,IFR was difficult to disperse uniformly in matrix because it was a multi-component system and their synergistic flame retardant effect was not satisfied.In order to a high flame retardant level,a large addtion amount of flame retardants were required.In the mono-component IFR,the gradients were incorporated into one molecule and could exert much better synergistic flame retardant effect.In this thesis,the intermediate bis(methylphosphonic acid)piperazine was firstly synthesized from methylphosphonic acid and piperazine,and then reacted with neopentyl glycol to prepare piperazine neopentyl glycol methylphosphonate ester(PPMPNG).Its chemical structure was characterized and confirmed by Fourier transform infrared spectroscopy,nuclear magnetic resonance spectroscopy and elemental analysis.The thermal properties of flame retardants were investigated by thermogravimetric analysis(TGA).The results showed that the initial of thermal decomposition temperature of flame retardants was 219.5?,and the char residue mass at 700? was 33.7 wt%,which indicated that PPMPNG possessed superior charring capability and thermal stability.PPMPNG was incorporated into polyethylene(PE)and the flame retardancy,thermal properties and flame retardant mechanism of PE materials were investigated.The samples with the thickness of 1.6 mm passed UL-94 V-0 rating during vertical combustion test,and the limiting oxygen index value was 25.6%when 23 wt%PPMPNG was introduced.According to the previously reported works,more or less 30 wt%IFR was required to fulfill the equal flame retardant grade of PF It indicated that PPMPNG exhibited excellent flame retardant efficiency for PE materials.Cone calorimeter(CONE)tests indicated that the peak value of heat release rate,total heat release(THR)and other combustion parameters of materials were considerably declined with the incorporation of PPMPNG.The expanded,continuous and compact char layer were generated on materials surface during combustion,which effectively inhibited the transfer of the heat and flammable gas between the combustion area and the matrix under char layer.The composition of pyrolysis products were analysized by pyrolysis-gas chromatography-mass spectrometry(Py-GC/MS)tests.The pyrolysis of flame retardants produced phosphine oxygen free radicals and it could effectively capture the active free radicals produced from polymers and then break the chain reaction of combustion,thus the flame was inhibited.PPMPNG exerted the flame retardant effect both in gas and condensed phase,and the PE materials were endowed highly flame retardant efficiency.PPMPNG was used to preparing flame retardant ethylene-vinyl acetate copolymer(EVA)composites.The samples achieved UL-94 V-0 grade and the LOI value was 26.8%when the loading amount the flame retardant was only 21 wt%.Compared with the previous reported works,PPMPNG showed much better flame retardant efficiency for EVA.CONE tests showed that the heat release rate and total heat release of EVA materials were significantly reduced with the introduction of PPMPNG.During the combustion process,the intumescent,integrated and compact of char layer was formed on materials surface and evoked effectively isolation effect.Thermogravimetric and infrared measurements showed that PPMPNG promoted the degradation and charring in advance on heating.Py-GC-MS revealed that PPMPNG inhibited the combustion of materials in gas phase.Moreover PPMPNG was also applied to preparing flame retardant polyethylene ethylene-octene copolymer(POE)composites and their performance were explored When the loading amount of PPMPNG was 21 wt%,the samples fulfilled UL-94 V-0 grade with the LOI value of 27.3%,and the POE composites with highly flame retardancy were obtained.TGA tests indicated that the addition of flame retardant enhanced the thermal stability and charring capability of the material at high temperature.Compared with pure POE,the values of HRR,PHRR and THR of flame retardant POE composites were significantly reduced.Flame retardants play both flame retardant roles in gas phase and condensate phase,and increased the charring flame retardance efficiency of POE materials.