A Novel Polymeric Flame Retardant Based On Dopo And Ferrocene Groups: Synthesis,and Application In Epoxy Resin And Polypropylene

Epoxy resin?EP?and polypropylene?PP?,as two important polymer materials,have been widely used due to their excellent physical and mechanical characteristics,low cost,and simple production process.Although EP and PP have so many advantages,their flammability characteristics limit their application in these areas requiring higher flame retardancy.Therefore,in this paper,a novel polyester flame retardant based on DOPO and ferrocene was synthesized aiming at improving the flame retardant efficiency of EP and PP,which was added to EP and PP as flame retardant and synergistic agent respectively.The following research works were carried out:A novel flame retardant,named as poly10-?2,5-dihydroxyphenyl?-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-1,1'-ferrocene dimethyl ester?PFDCHQ?,was prepared from ferrocene and DOPO-HQ as raw materials.And its chemical structure was comfirmed by FTIR and ¹H NMR.GPC and DSC tests showed that the number average molecular weight and glass transition temperature of PFDCHQ were 10080 g/mol and 92.4 ^oC,respectively.In addition,the TG test results of PFDCHQ in nitrogen and air atmosphere showed that PFDCHQ exhibited excellent thermal stability in both atmospheres.Therefore,the TG-FTIR and Py-GC/MS ananlysis methods were used to study its pyrolysis behavior.The results showed that PFDCHQ produced a large number of aromatic compounds such as naphthalene,anthracene and phenanthrene in the thermal cracking process,a nd it was inferred that DOPO released PO and PO₂ radicals during degradation.PFDCHQ was used as flame retardant to modify the EP.The combustion properties,flame retardancy and smoke suppression performance of EP composites were tested by LOI,UL-94 and cone calorimetry?CC?.The results of LOI and UL-94 expriments indicated that only adding a proper amount of PFDCHQ can make the EP/PFDCHQ composites?EP-5 and EP-6?reach the V-0level.CC data showed that the peak heat release rates of EP-5 and EP-6 were939.3 k W/m² and 872.3 k W/m²,which were lower than EP-0?1146.1 k W/m²?,and the peak smoke release rate were also significantly reduced.It was found that the release of hydrocarbons and aromatic compounds for EP-5 and EP-6 was far lower than EP-0 by analyzing the TG-FTIR,indicating that lots of hydrocarbons and aromatic compounds remained in the condensed phase to form char layer.The Raman and SEM analysis of the char after UL-94 test illustrated that it is more conducive to form high degree of graphition and compact char layer for EP/PFDCHQ composites with 5 wt%PFDCHQ.PFDCHQ,as a novel synergistic fire retardant agent with IFR?APP/PER,a mass ratio of 3:1?,was incorporated in PP to prepare a seris of PP/IFR/PFDCHQ composites.The results of LOI and UL-94 tests suggested that PP-2?PP76/IFR23.5/PFDCHQ0.5?and PP-3?PP76/IFR23/PFDCHQ1?can reach V-1rating with good flame retardant effect in many systems.However,the V-1 level was obtained for PP-1?PP76/IFR24?,indicating that there is a synergistic flame retardant effect bwteen PFDCHQ and IFR.The TG data showed that the initial decomposition temperature(T_-5%)of PP-2 and PP-1 were advanced to 317 ^oC and 319 ^oC respectively compared with PP-1?336 ^oC?due to the catalytic degradation of ferrocene.The results of Raman and SEM experiments for the residual carbon after UL-94 test of PP composites indicated that the degree of graphitization and compactness of PP-2 and PP-3 is higher than PP-1,which is more conducive to preventing the transimission of fire and heat and protect the internal materials from continuing to burn and achieve the purpose of flame-retardant.