Design And Synthesis Of Two DOPO Derivatives And Their Application In EVA/MH Composites

9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)derivatives have been employed as flame retardant in polymer due to their high thermal stability,excellent flame retardancy and synergistic effects with other flame retardents.Herein,two DOPO derivatives labelled as OA-DOPO and PER-3DOPO were synthesized and imported to ethylene-vinyl acetate copolymer(EVA)/magnesium hydroxide(MH)composites and the influence of DOPO derivatives with different structures on EVA/MH composites was studied.It could be instructive for the structure design of DOPO derivatives.1 OA-DOPO or PER-3DOPO were synthesized by addition reaction between DOPO and octadecyl acrylate(OA)or pentaerythritol triacrylate(PETA),respectively,and their chemical structures were confirmed by nuclear magnetic resonance spectroscopy(NMR)and mass spectrometry(MS).The thermal stability of two DOPO derivatives was investigate by thermogravimetric analysis(TGA).Compared with DOPO,the initial decomposition temperature(T5%)of OA-DOPO and PER-3DOPO increased from 211.3℃ to 318.7℃ and 389.0℃,repectively,which enable two DOPO derivatives could be tolerable for compounding with most commodity thermoplastics at high temperature.Moreover,the aggregation states of two DOPO derivatives were characterized by different scanning calorimetry(DSC)and X-ray diffraction(XRD).OA-DOPO was a crystalline compound and its melting point(Tm)was 60.8℃.PER-3DOPO was an amorphous compound and its glass-transition temperature(Tg)was 70.9℃.Besides,fluorescent performance of two DOPO derivetives was expolerd by fluorescent characterization.Under excitation of UV light,OA-DOPO and PER-3DOPO emited light ranged 325～450 nm and 380～550 nm,respectively.2 OA-DOPO was applied as synergistic flame retardants in EVA/MH composites.The results indicated that OA-DOPO was beneficial for the dispersion of MH particles in EVA matrix due to its special structure,and the thermal stability and limiting oxygen index(LOI)of EVA composites has been improved by the incorporation of OA-DOPO.As 2wt%content of MH was replaced by OA-DOPO,melt mass-flow index(MFR)increased from 0.87 to 1.66 g/10 min and the complex viscosity(η*)tested by rheological characterization decreased,which showed better processability.And the flexibility of EVA/MH composites was improved by OA-DOPO,the elongation at break increased from 180.6%to 263.6%while 2wt%content of MH was replaced by OA-DOPO.Besides,the fluorescent performance of OA-DOPO was exploited as fluorescent brighten agent in EVA/MH composites,which facilitated EVA composites for light-colored products.3 In order to futher invesitigate the synergitism between DOPO derivatives and MH,PER-3DOPO also served as synergistic agent in EVA/MH composites,and the flame retardency of EVA/MH/PER-3DOPO ternary composites was investiged by LOI and cone calorimeter test(CCT).It was proved that PER3DOPO enhanced the fire performance of EVA composites.Compared to the EVA/50%MH sample,the LOI increased from 24.0%to 31.5%,the time to peak heat release rate(Tp-HRR)increased from 165 s to 215 s,the peak heat release rate(p-HRR)decreased from 741.8 kW/m2 to 365.1 kW/m2,and the fire performance index(FPI)increased from 0.066 to 0.140,as 2.25wt%content of MH was replaced by PER-3DOPO,which could give people more escape time in a fire.It was proved that PER-3DOPO exerted flame retardant in condensed phase by the calcination experiment in muffle furnace,which could promot EVA composites to produced more protective char during combustion.Meanwhile,PER-3DOPO can also acted as fluorescent brighten agent in EVA/MH composites,which could wightened and brightened EVA/MH composites.