Synthesis Of Flame Retardant Based On Phospha-phenanthrene And Its Application In Epoxy Resin

The traditional halogen flame retardant was restricted by many countries because of its biological enrichment and the formation of toxic burners in the combustion process.Phosphorus-based flame retardants have attracted much attention due to its low smoke,low toxicity and other advantages.At present,the epoxy resin?EP?was widely used in many fields because of its excellent performance and low cost,but it's flammable.This shortcoming has limited its application,so the research on flame-retardant modification has become the current research hotspot.A series of novel phosphaphrnanthrene derivations were synthesizes through the substitution and addition reaction,then they were used in the study of EP's flame retardant modification.The specific research contents and test results were as follows:?1?6H-dibenzo[c,e][1,2]oxaphosphinine-6-sulfide?DOPS?was synthesized through the reaction of DOPO and phosphorus pentasulfide?P₂S₅?.A series of novel phosphaphrnanthrene derivations,2-??6-sulfido-6H-dibenzo[c,e][1,2]oxaphosphinin-6-yl?methyl?succinic acid?DOPS-ITA??6-?1,4-dihydroxynaph-thalen-2-yl?-6H-dibenzo[c,e][1,2]oxaphosphinine 6-sulfide?DOPS-NQ??6-phenoxy-6H-dibenzo[c,e][1,2]oxaphosphinine 6-sulfide?DOPS-BQ?and other substances were synthesized by addition reaction.The structure of the synthesized compounds were characterized and investigated by Fourier Transform Infrared Spectroscopy?FT-IR?,nuclear magnetic resonance?NMR?and so on.Thermogravimetric Analysis?TGA?was used to analyze the thermal properties of DOPS and some of its derivatives.The results showed that DOPS-BQ has only one degradation process,and its R_700?was 0.75%;DOPO and DOPS-NQ have two degradation processes,but DOPO basically decomposed completely at 550?,while DOPS-NQ R_700?was 18.05%.DOPS and DOPS-ITA have three degradation processes,their R_700?were 10.5%,13.18%respectively.?2?EP were modified by DOPO?DOPS?DOPO/APP?DOPS/APP,and the performance of FR-EP were studied with limit oxygen index?LOI?value,UL-94,TGA and other testing methods.The results showed that the addition of FR could effectively improve the flame retardant properties and the carbon formation ability under high temperature conditions;and the compounded FR exhibited better flame retardant effect.At the same time,it could be seen from its Cone calorific test?CONE?that the addition of FR effectively reduced the peak values of Heat Release Rate?pK-HRR?,total Heat Release?THR?and total Smoke Product?TSR?etc.Scanning electron microscopy?SEM?analysis of its carbon residue showed that FR-EP has formed a continuous,dense carbon layer after combustion,and honeycomb-like dense continuous carbon layer has appeared in the DOPS/APP-EP system.?3?The performance of the FR-EP system was tested and analyzed.The results showed that the addition of FR could effectively improve the LOI values and UL-94 rating of the substrate;and the flame retardant performance of DOPS-NQ and its complex resistance system were better than that of DOPS-ITA and its complex system.At the same time,the addition of FR could effectively reduce the values of HRR,EHC and THR;and also could reduce the production of CO and CO₂ of FR-EP.The SEM analysis of FR-EP showed that the residual char modified material had formed a closed carbon layer foam structure.In the DOPS-BQ-EP and DOPS-BQ/APP-EP systems,the flame-retardant properties exhibited were similar to those of the previously studied flame-retardant systems.In the FR-EP,the compound FR has a smoke suppression effect on the EP,but in the DOPS-BQ-EP system,the SPR and TSR values were increased.This was mainly related to the carbon residue structure formed at high temperatures.It could be observed from the SEM images that the internal morphology of the carbon layer of the DOPS-BQ-EP system was similar to that of pure EP,with a large number of holes.The carbon layer generally cannot have the effect of good insulation,oxygen,and could not better prevent the gas inside the substrate from escaping into the combustible region,so this also indirectly led to the SPR and TSR value increased.