| To improve the flame retardancy of polymer materials and promote the wide application of polymer materials,additive and reactive flame retardants are usually used to improve the flame-retardant performance of polymer materials.However,the additive flame retardants,especially small molecule of additive flame retardants have poor compatibility with matrix and have bad influences on mechanical properties.In addition,the additive flame retardants are easy to migrate and precipitate.Reactive flame retardants can introduce flame-retardant elements into the molecular chain of polymer materials through molecular design,which can improve the flame-retardant properties without deteriorating the mechanical properties.In this paper,two kinds of reactive flame retardants and one kind of polymeric flame retardant were synthesized and used in unsaturated polyester resin(UPR),which were proved to have good effects on improving the flame-retardant properties of UPR.The main research contents are as follows:(1)The caged structure of 1-thio-4-hydroxymenthyl-2,6,7-trioxal-1-phosphabicyclo[2.2.2]octane(SPEPA)was synthesized by using thiophosphoryl chloride and pentaerythritol as raw materials.Then the reaction of SPEPA with methyl vinyl dichlorosilane was carried out to synthesize methyl vinyl di(1-thio-2,6,7-trioxal-1-phosphabicyclo[2.2]octane-4-methoxy)silane(MVDOS),and the optimal condition was determined.The solvent was dioxane,n(SPEPA):n(methyl vinyl dichlorosilane)=2.2 and the reaction time and temperature were 8 h and 90?,respectively.MVDOS was characterized by fourier transform infrared(FTIR),nuclear magnetic resonance(NMR),elemental analysis and thermogravimetric analysis(TGA).The initial decomposition temperature of MVDOS was 220?and residual carbon was 31.4 wt%at 800?.MVDOS was utilized as a reactive flame-retardant monomer to modify UPR.The UPR/MVDOS composites were prepared by introducing different rations of MVDOS into UPR via the reaction of crosslink and characterized by FTIR.The flame-retardant performance of the UPR/MVDOS composites was investigated by using the limiting oxygen index(LOI),vertical burning test(UL-94),and cone calorimeter(CONE)test.The results indicated that the composites reached the V-0 rate and the LOI value was 29.1%when the content of MVDOS was 18 wt%.Cone calorimeter tests revealed the peak of heat release rate and CO production rate of UPR/MVDOS-18 were 238.2 k W/m~2 and 0.0167 g/s,which was respectively lower than the ones of neat UPR.The introduction of MVDOS increased the stability of UPR composites.Furthermore,the scattering electron microscopy(SEM),laser Raman spectroscopy(LR),and X-ray photoelectron spectroscopy(XPS)studies revealed that the incorporation of MVDOS stimulated the UPR matrix to generate char layer with increased graphitization degree,which provided a good barrier to prevent heat and oxygen from being transferred.It is consistent with flame-retardant mechanism of condensed phase.(2)Polymeric flame retardant poly methyl vinyl di(1-thio-2,6,7-trioxal-1-phosphabicyclo[2.2]octane-4-methoxy)silane(PMVDOS)was prepared by polymerization of MVDOS and the optimal synthesis condition was determined as follow:the solvent and initiator were N,N-dimethylformamide(DMF)and azo-iso-butyronitrilee(AIBN),and the reaction temperature and time were 75?and 5 h.PMVDOS was characterized by FTIR,NMR and TGA.The results of TGA showed that the initial decomposition temperature of PMVDOS was 261?which was 41?higher than that of MVDOS and residual carbon was23.2wt%at 800?,which indicated that PMVDOS had good thermal stability.The UPR/PMVDOS composites were prepared by adding PMVDOS into UPR.The flame-retardant properties,micromorphologies and structure of the char layer of UPR samples were measured by LOI,UL-94,CONE,SEM,LR and XPS.The results showed that the LOI value of UPR/PMVDOS composite was 27.8%,reaching the UL-94 V-0 and the carbon residue increased from 4.9%of pure UPR to 14.9%when the content of PMVDOS was 18 wt%.The peak of heat release rate,total heat release and total smoke production of UPR/PMVDOS-18composite were 300.7 k W/m~2,89.5 MJ/m~2 and 38.3 m~2,respectively,which were reduced by 46.0%,25.3%and 18.3%compared with neat UPR.The flame-retardant mechanism of PMVDOS mainly acted on the condensed phase.The surface of the matrix was covered with the polymer containing phosphorous and silicon dioxide particles,which prevented the escape of flammable volatiles and isolated the exchange of oxygen and heat.So the degradation of matrix was inhibited.(3)Maleic acid mono(1-thio-phosa-4-hydroxymethyl-2,6,7-trioxa-bicyclic[2.2.2]octan-4 methylene)ester(MA-SPEPA)was synthesized by using SPEPA and maleic anhydride(MA)as raw materials,and the optimal condition was determined as follow:the reaction temperature,time and the molar ration of MA and SPEPA were 60?,3 h and 1:1,respectively.MA-SPEPA and Chitosan(CH)were used as raw materials for the synthesis of the inflatable flame retardant maleic acid single SPEPA ester chitosan salt(CH-MA-SPEPA)containing active monomer.The effect of CH-MA-SPEPA on the mechanical properties,the flame-retardant properties and the thermal degradation behavior of UPR was studied by mechanical test,LOI,UL-94 and TGA.The results showed that the LOI value of UPR2sample was 28.1%,reaching UL-94 V-0 and the carbon residue in air increased from 2.2%of pure UPR to 7.1%when the content of CH-MA-SPEPA was 18 wt%.The test of CONE showed that the heat release rate(HRR),total heat release(THR),smoke production rate(SPR)and total smoke production(TSP)values of UPR materials were significantly inhibited by the introduction of CH-MA-SPEPA.The HRR,THR and TSP values of UPR2were reduced by 31.7%,30.3%and 14.7%compared with these of pure UPR.The flame-retardant mechanism of CH-MA-SPEPA indicated that the expanding and dense carbon layer and non-combustible gas played an important role in the protection of UPR material.(4)The addition of these three flame retardants all improve the flame retardancy of UPR,which provides the possibility for the wide application of UPR. |
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