Research On The Flame-retardant Property Of EPDM

Ethylene-propylene-diene monomer rubber(EPDM) with acombination of excellent resistance to a number of environments suchas weathering, heat, ozone, and chemicals, hydrolysis, is produced bycopolymerizing ethylene, propylene and small amount of non-conjugateddiene, which provides the pendent double bonds of EPDM. EPDM iswidely used in transportation, construction, electrical/electroniccomponents and many other fields closely related with people’s daily life.Nevertheless, flammable EPDM with a low limited oxygen indexvalue(about19%), releases large amount of heat and smoke, whichextremely restricts its wide application. In this way, it is particularlynecessary and important to improve the flame-retardant property ofEPDM. Aluminum diethylphosphinate(ADP) is a new kind of greenflame retardant developed in recent years. With high thermal stability andhigh content of phosphorus, environment-friendly ADP has been usedin the field of flame-retardant polymers, such as nylon material, in whichADP exhibits excellent flame-retardant property, mechanical propertyand electrical property. In order to enhance the thermal stability andflame-retardant property of EPDM, we have prepared flame-retardantEPDM by adding ADP and ADP composited with melaminepolyphosphate(MPP). Besides, we have also choosen expandablegraphite(EG) and octavinylsilsequioxane(OVP) as flame retardantsynergistic agent to discuss the effects of different flame-retardant systemon the combustion property and mechanical property of EPDM.Based on limited oxygen index (LOI), heat releaseing, smokereleasing and thermal stability, combustion property of ADP/EPDMcomposites is studied and compared by LOI, CONE, smoke chamber andTGA. The result shows that when the additive amount of ADP is30phr,the limited LOI can reach35%and heat release rate(HRR), total heatrelease (THR), total smoke rate (TSR), the smoke density(Ds), areeffectively decreased.What is more, ADP can enhance thermal stabilityof EPDM and delay thermal degradation of EPDM.In order to increase the phosphorus content of the system and improve the flame-retardant property of EPDM, we preparedflame-retarded ADP/MPP/EPDM composites based onphosphorus-nitrogen synergistic effect. The impacts of different massratio and the additive amount of ADP/MPP flame retardant oncombustion property and mechanical property of EPDM are studied andcompared. Compared with ADP/MC and ADP/MCA compounding flameretardant, ADP/MPP show the best flame retardant property on EPDM.The result shows that when the mass ratio of ADP/MPP is2:1and theadditive amount is30phr, the limited LOI can reach36%, and the peakof heat release rate reducing50.2%, the total heat release reducing25.9%, the total smoke production reducing22.3%, and the index ofheat release and smoke release all reached the minimum level, in whichthe composites has best flame retardant property. Increasing the contentof carbon black N330can improve combustion property and smokesuppression of EPDM.Effects of other additives-EG and OVP on combustion property andmechanical property of ADP/MPP/EPDM system are studied. The resultsshow that the HRR、THR、TSR of composite can be reduced futher byadding EG, but the LOI and mechanical property ofcomposite were damaged. On the other hand, although OVP canincrease the crosslinking density of EPDM vulcanizates and improve themechanical properties of composite, influence on the combustionproperty of EPDM is not obvious.