Synthesis、 Properties And Curing Dynamics Research Of Novel Synergism Of Phosphorus-nitrogen Flame Retardant Epoxy Resin Curing Agent

Recently, traditional epoxy molding compounds are facing great challenges with thedevelopment of the electronics and composite materials, the conventional epoxy resins areunable to satisfy some applications, which require higher thermal resistant, better flameretardant and lower moisture absorption. Thus, it is necessary to design and develop highthermal resistant, good flame retardant and low moisture absorption epoxy resin systems forthese applications.This paper introduces a kind of epoxy resin curing agent synthesis method and processfrom the molecular structure design. A novel synergism of phosphorus-nitrogen flameretardant epoxy resin curing agent for epoxy resins, was synthesized via condensationreaction of4-hydroxybenzaldehyde with melamine, followed by the addition of9,10-Dihydro-9-oxa-10-phosphaphen-anthrene10-oxide （DOPO） to the resulting imine linkage. Chemicalstructures of these materials were characterized with FTIR,¹H-NMR spectra,³¹P-NMRspectra. The thermal and flame retardant properties of the epoxy resins cured by variousequivalent ratios phenol formaldehyde nolovc （PN） and P-MSB were investigated by thenonisothermal differential scanning calorimetry （DSC）, the thermogravimetric analysis（TGA）, and limiting oxygen index （LOI） test. The obtained results showed that the curedepoxy resins possessed high T_g（165oC） and good thermal stability (T_10%,353oC). Moreover,the P-MSB/CNE systems exhibited higher LOI （35） and more char was maintained inP-MSB/CNE systems than that in PN/CNE system and the effective synergism ofphosphorus-nitrogen indicated their excellent flame retardancy.The curing kinetics of CNE in presence of P-Containing melamine Schiff base （P-MSB）was explored by non-isothermal differential scanning calorimetry （DSC） technique. The basiccure process was determined through extrapolation. The Flynn-Wall-Ozawa isoconversionalmethod and Kissinger method were used to evaluate the effective activation energy （Ea） was74.18and70.17kJmol^-1, respectively. The curing mechanism was given by the Friedmanmethod. The autocatalytic kinetic model was found to be the best description of theinvestigated curing reactions. The reaction order m and n are0.95and2.03respectively.Non-isothermal DSC curves obtained from the experimental data showed a good agreementwith that theoretically calculated.