Research On Flame Retardant Modification And Mechanism Of EPDM Rubber Flame Retardant Materials

In this paper,a series of formulations for halogen-free flame retardant modification of EPDM were designed from the aspects of reinforcing agent,flame retardant system and compatibilizer,and tensile testing machine,oxygen index tester(LOI),vertical combustion tester(UL94),cone calorimeter(cone),thermogravimetric analyzer(TGA)and scanning electron microscope(SEM)were used The effects of carbon black N550 reinforcing agent,ammonium polyphosphate / triazine charring agent compound intumescent flame retardant(APP / CFA),metal hydroxide flame retardant,zinc borate flame retardant synergist and ethylene propylene diene monomer grafted maleic anhydride(epdm-g-mah)compatibilizer on the comprehensive properties of EPDM materials were studied,and the internal flame retardant mechanism and performance influence law were explored.Firstly,the effect of reinforcing filler carbon black N550 on the properties of EPDM materials was studied,and the better basic formula of EPDM was determined.The results showed that carbon black N550 could improve the mechanical properties and flame retardant properties of EPDM at the same time,and promote the carbonization behavior of EPDM materials.When the content of carbon black N550 is30 phr,the comprehensive properties of EPDM composites are the best,and the tensile strength is 10.35 mpa,which is increased by 3.4 times;Loi increased from 18.1% to21.1%;The maximum heat release rate decreased by 52% and the total heat release decreased by 10%;The carbon residue rate is increased by nearly 4 times,and the morphology of carbon layer formed after combustion is continuous.Secondly,based on the basic formula reinforced by carbon black,the intumescent flame retardant app / CFA was introduced to modify the flame retardant of EPDM system,the effect of APP / CFA on the properties of EPDM was studied,and the intumescent flame retardant mechanism of APP / CFA was explored by TGA and SEM.The results show that when the total amount of intumescent flame retardant is 90 phr and the ratio of app and CFA is 3:1,the flame retardant effect is the best,but the mechanical properties decrease.Loi reached 32.2%,UL94 level was V-0,and the maximum heat release rate was 263.67kw/m2,a decrease of 59%.At the same time,APP / CFA has good carbonization effect and efficiency,making the carbon layer more dense and uniform,which is conducive to the structural stability and thermal stability of EPDM.In addition,the effects of the composite flame retardant system composed of magnesium hydroxide and aluminum hydroxide as flame retardants and zinc borate as flame retardant synergistic agents on the properties of EPDM were studied,and the synergistic flame retardant mechanism was explored by TGA and SEM.The results show that zinc borate and metal hydroxide,magnesium hydroxide and aluminum hydroxide have good synergistic flame retardancy.When the total addition amount of metal hydroxide is 105 phr,the optimal ratio of magnesium hydroxide to aluminum hydroxide is 5:2,the optimal addition amount of zinc borate is 35 phr,and the LOI is30.4%.The UL94 test passes the V-0 grade for the first time,the average heat release rate is reduced by 25% and the total heat release amount is reduced by 20%;The tensile strength is 10.62 mpa,showing an increasing trend for the first time,which makes up for the damage of mechanical properties caused by the large addition of hydroxide flame retardant to a certain extent.Finally,the effects of ethylene propylene diene monomer grafted with maleic anhydride as compatibilizer on the compatibility between EPDM and other components and on EPDM intumescent flame retardant system were studied.The results show that an appropriate amount of pdm-g-mah can greatly improve the interfacial compatibility between EPDM matrix and filler particles,and make the inorganic filler disperse more evenly.When the content of epdm-g-mah was 20 phr,the comprehensive properties of EPDM intumescent flame retardant system were further improved,the tensile strength was 8.66 MPa,increased by 13%,and the elongation at break was 702%,which remained at the same level as before the addition of epdm-g-mah;Loi was 33.4%,UL94 was V-0,the average heat release rate decreased by 44%,and the total heat release decreased by 23%.