Design Of Phosphatphenanthrene Flame Retardant And Study On Performance Of Synergistic Flame Retardant Modified Epoxy Resin Composite

In order to study the flame retardancy of halogen-free flame retardants with low toxicity and green environmental protection in epoxy resin composites,the multi-element and nano-material flame retardants was focused on the current research.Among them,phosphate-nitrogen flame retardants are the most dominant flame retardants,because of their low smoke and toxicity.Nanomaterials are present in epoxy resins by means of addition or reaction.They can make a very small amount of nanomaterials have certain flame retardancy.In this paper,a methoxyphosphorous heteropolymer flame retardant was designed and synthesized by two-step method.Then new phosphorus flame retardants,nitrogen flame retardants,nanomaterials(graphene)compound flame retardant,respectively to construct P,P/N,P/GR,P/N/GR four kinds of synergistic flame retardant epoxy resin system,their flame retardant properties,thermal stability,mechanical properties,thermal cracking material and carbon residue morphology,mechanism were analyzed in this paper.Our work provided new ideas and perspectives for the research of P,P-N and nanocomposites.The research contents of this paper are as follows:(1)The flame retardant methoxyphenoxyphosphate(MODOP)was synthesized from phosphorus oxychloride,p-methoxyphenol,and 6-(2,5-dihydroxy-phenyl)-6H-dibenzo[c,e][1,2]oxaphosphinine 6-oxide(ODOPB).The structure of flame retardant was characterized by FTIR,1H NMR,31 P NMR,13 C NMR and XPS.The thermal stability of flame retardant MODOP was studied by thermogravimetric analysis.The results of thermogravimetric experiments showed that the MODOP started to decompose at 328? and the amount of residual char was 33.0% at 700?.Compared with the flame retardant additives reported in the laboratory,MODOP had good thermal stability and carbonization ability.(2)The prepared MODOP flame retardant was compounded with ammonium polyphosphate(APP)(1:2),and the flame retardant performance of epoxy resin was studied and analyzed by limiting oxygen index(LOI),vertical combustion test(UL-94)and cone calorimetry test(CONE).Mechanical properties of modified epoxy resin were analyzed by universal testing machine.Thermal stability of epoxy resin can also be used to analyze by thermogravimetric and thermogravimetric infrared.The above results show that when the 10wt% MODOP was added in epoxy resin,the LOI increases by 18.86% compared with the pure EP.When the MODOP/APP addition amount reached 20wt%,the LOI reached 34.5%,which was 42.61% higher than the pure EP.Both av-HRR and PHRR of the modified EP show a decreasing trend,especially when 15wt%MODOP/APP was added in epoxy resin,the PHRR value between the modified EP and pure EP decreases by 65.92%.According to the results of thermogravimetric data,the carbon residue rate of pure EP was 16.53% at 700?.The carbon residue rate could reach up to 29.98%,when addition of MODOP and MODOP/APP composite flame retardants was increased in epoxy resin.It was found that the characteristic absorption peaks of phosphate ester and N-H were released when the composite was decomposed by TG-IR.(3)MODOP,APP and graphene were combined with epoxy resin for flame retardant modification.The results showed that 1.0wt% grapheme LOI value of the epoxy resin was the same as 5wt% MODOP-EP.The LOI value of 20wt%GR/MODOP/APP-EP was 34.7%,which increased by 43% compared with the pure EP,and the UL-94 reached the V-0 level.Compared with PHRR,HRR,THR and other parameters,the modified EP has good carbon forming effect and excellent flame retardant performance,which is helpful to reduce the fire risk.MODOP/GR is more helpful to promote EP carbonization and more maintain thermal stability than GR/MODOP/APP at high temperature.The strength of some functional groups was significantly reduced by C=O,C-O-C and aromatic compounds by TG-IR,when graphene or APP were added in epoxy resin.It is indicating that the addition of flame retardants could reduce toxic gas or the addition of carbon layer could prevent the toxic gas from escaping.The results of XPS and Raman analysis show that compound systems have the flame retardant mechanism of condensed phase and gas phase at the same time.