| Ethylene vinyl acetate (EVA), because of its excellent mechanical and chemical properties, has been widely applied in many areas such as wire and cable, construction, household appliances. However, EVA is easy to catch fire and its limiting oxygen index (LOI) value is only 18%. Therefore it must be flame retardated in many eares before it is used. In recent years, because of environmental reasons, the application of halogen containing flame retardants is restricted, therefore, the demand for flame retardant material of halogen-free and environmentally friendly is growin. Nitrogen and phosphorus intumescent flame retardant (IFR) has low toxicity and low smoke characteristics, Expandable graphite (EG) has non-toxic and low smoke characteristics which are both meet the development trend of green environmental protection, has become a hot research of intumescents. But they are almost no reports of EVA which is flame retardanted Synergisticlly by EG and IFR (acide source, APP; carbon source, PER; gas source, MEL). In this paper, flame-retardant EVA resin is the research objective, three flame retardants are choiced which are the P-N intumescent (IFR), expandable graphite (EG) and synergistic flame retardant of them.The burning behavior, thermo-gravimetric behavior, thermal degradation kinetic and char structure of flame retardant EVA were studied by the testing methods such as cone calorimeter testing (CONE), UL-94 vertical burning testing, TG and SEM in order to obtain flame retardant EVA used under various requirement. Flame retardant mechanism and synergistic effect were also discussed. The main contents are as the follows.The IFR flame retardant EVA system was studied. Through the use of IFR different quality and quantity of fire-retardant EVA ratio. IFR can improve the combustion properties of flame retardanted EVA compared to pure EVA, when the quantity ratio of APP: PER is 4:1, the oxygen index was highest, which can be reached 28.5%, when MEL was added in flame retardante, the combustion property declined. Through the CONE testing, it proved flame retardant mechanism of IFR is condensed phase flame-retardant, the addition of IFR system can effectively reduce the HRR, MLR and SPR, etc., and has a good smoke suppression.The EG flame retardant EVA system was studied. EG with dIFRerent particle size was used to flame retardant EVA. The results show that: the combustion properties of composite materials enchanced significantly because of the addition of EG, especially in the oxygen index increased significantly. The material with dIFRerent particle size EG has dIFRerent flame-retardant effect, flame retardant is better with increasing of particle size of EG, but the physical properties wasworse. CONE tests show that, the PHRR, MHRR, PMLR and MMLR of EG flame retardant EVA system have"Single peak before"feature, reflecting the typical condensed phase flame retardant mechanism. Char layer formed has good quality which can subjecte to high temperature. The char can isolate oxygen and heat which plays a role in inhibiting the degradation of EVA matrix, while to protect cross-linked arbon products of EVA.The synergistic flame retardant EVA system by EG and IFR was studied.The results show that, EG and IFR have good Synergistic effect. When the mass ratio of them is 1:1, flame-retardant effect is best. The mechanism is also condensed phase flame retardant mechanism when they are synergisticlly used to flame-retardant EVA. The data of EHC and MLR is lower than they used singly.The carbon layer structure is more compact which has better flame retardant effect. |
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