| Because of its high bonding performance, good electrical insulation and excellent corrosion resistance, epoxy resin is widely used in electronic and electrical fields. With the rapid development of electronic and electrical industry, people set a higher request to the material property of EP encapsulation than before correspondingly. The traditional halogen-containing flame retardant epoxy resin hasn't adapted to the requirement of the electronic and electrical industry yet, so the exploitation and application of halogen-free flame retardant epoxy resin has become an important research direction of epoxy resin materials. Phosphorus-nitrogen flame retardant epoxy resin has the characteristics of high flame retardant efficiency, non-toxic and smoke suppression, and it conforms to the future direction of the electronic and electrical industry. The elements of nitrogen and phosphorus are introduced to epoxy resin from designing the molecular structure. A kind of imine (PDA) is synthesized via a condensation reaction of 4-hydroxybenzaldehyde with diethylenetriamine, then a curing agent (PDA-DOPO) for an epoxy resin with synergism of phosphorus-nitrogen flame retardant is synthesized by an addition reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthracene-10-oxide (DOPO) with PDA. Chemical structures of those materials are characterized with FTIR and 1H NMR spectra,In this paper, PDA-DOPO is used as the curing agent of epoxy resin, and then different phosphorus contents of flame retardant epoxy resins are prepared. The curing process is characterized with FTIR. The thermal and flame retardant properties of the epoxy resins are investigated by dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), vertical burning test and cone calorimetric test, respectively. The results show that the cured epoxy resins possess good thermal stabilities and flame retardant performance. Flammability of the epoxy thermosets (based on the account of phosphorus content of 1.00 wt.%) meet requirements with a grade of V-0 in the UL-94 flammability standard and its limiting oxygen index is 29. Its initial decomposition temperature is at 335 ?. Its glass transition temperature (Tg) is 163 ? and char residual is 21.6% at 600 ?. The cone calorimetry results show that with the increase of the addition amount of flame retardant, all of the heat release rate, the total heat release, the smoke production rate and the total smoke production gradually reduce. However, the carbon residual is on the contrary.Thermal degradation mechanism of the epoxy thermoset with phosphorus content of 1.00 wt.% [(P-1.00)/DDS/DGEBA] is investigated with TGA. The kinetic parameters of (P-1.00)/DDS/DGEBA system are determined by Kissinger, Ozawa, Flynn-Wall-Ozawa, and Frieman methods. The estimate values of activation energy in Kissinger, Ozawa, Flynn-Wall-Ozawa and Friedman methods are 201.7,212.7,223.5 and 232.7 kJˇmol-1, respectively. Coats-Redfern and Master curves kinetic methods are used to discuss its thermal degradation mechanism. It is found that the thermal degradation mechanism of (P-1.00)/DDS/DGEBA system follows the principles of nucleation and growth controlled reactions.In this paper, nano-silica and zinc borate are selected as smoke suppression of phosphorus-nitrogen flame retardant epoxy resin, and the flame retardancy is also discussed in the way of adding smoke suppression. The results show that the epoxy resin composite has excellent flame retardancy when the addition quantity of nano-silica reaches 3%. When the addition quantity of zinc borate reaches 8%, the total smoke production is decreased by 31.93%. It is concluded that the synergetic effect is well by adding zinc borateand PDA-DOPO phosphorus-nitrogen flame retardant. |
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