Synthesis Of A Novel Multifunctional Bisphosphate And Its Flame-retardant Application

Multifunction is an important direction for the development of polymer additive.A main approach is to introduce different functional groups into one molecule to achieve multifunction.In this paper,we synthesize a novel multifunctional bisphosphate which not only function as flame retardant,but also ultraviolet light absorber.It possesses simple preparation process,high thermal stability and low volatile,has a broad application prospect.The main content is listed below:Firstly,we synthesized spirocyclic pentaerythritol bisphosphate disphosphorychloride（SPDPC）as intermediate from pentaerythritol and phosphorus oxychloride.Then,a novel multifunctional bisphosphate（MFR）was synthesized starting from SPDPC and 2,4-dihydroxybenzophenone（UV-0）by substitution reaction.The chemical structure was confirmed by FTIR,NMR and HRMS,its thermal stability was studied by TGA.We prepared different flame retardant EP/MFR thermosets using epoxy resin as base material.The impact of different amount of MFR on the flame-retardant performance for EP was evaluated by limited oxygen index（LOI）,UL 94 vertical burning test and cone calorimeter test（CCT）.When 20 wt.% MFR was incorporated,the LOI value of epoxy thermoset increased to 33.2%,and a UL 94 V-0 classification was attained.Compared to neat EP,the cone calorimeter test indicated the total heat release（THR）and the total smoke release（TSR）of EP/20%MFR thermoset were reduced by 24.5% and 23.6%,respectively.The decomposition behavior was also studied by TGA.In addition,the flame retardant mechanism of EP/MFR was investigated in detail.The morphology and structure of the residual chars were observed by SEM and LRS.It was found MFR was an excellent carbonizing agent which can generate phosphorouscontaining acids to promote EP thermosets dehydrate to form stable char layers which could protect the underlying matrix from decomposition.MFR mainly works in condensed phase which is effective in charring polymer as epoxy resin.Besides,the UV absorption of MFR was studied in 5×10^-5 M acetonitrile（CH₃CN）,which demonstrated the superior ultraviolet light absorption capability of MFR over UV-0.