Flame Retardancy And Ceramic Properties Of EPDM Rubber Composites

Ethylene-propylene-diene rubber(EPDM)is the commonly used polymer in wire and cable.The limiting oxygen index of EPDM is only 17.8%,which is a flammable material,and it will release a large amount of heat and smoke during combustion,which limits the application of EPDM in the wire and cable industry.Therefore,it is necessary to carry out research on flame-retardant EPDM materials.Meanwhile,in addition to the certain flame retardant properties of wire and cable materials,they also need to have certain fire resistance properties to ensure the smooth flow of power systems and communication networks in the event of fire.Adding a certain amount of ceramic component to the cable material to promote the formation of ceramic body in the case of fire is the main way to improve its fire resistance of the materials.Therefore,it is of great significance to study the flame retardancy and ceramic properties of EPDM materials.Firstly,traditional intumescent flame retardant systems(IFR,APP/PER)and expandable graphite(EG)were used as flame retardants to prepare intumescent flame retardant EPDM composites.The effects of IFR and EG on the flame retardancy,thermal stability and combustion behavior of EPDM were studied using limit oxygen index test,vertical combustion test,thermogravimetric test and cone calorimetry test.The results show that,the flame retardant efficiency is average when IFR and EG are used alone.When IFR and EG are used in combination,they exhibit excellent synergistic flame retardant effects.And,when the ratio of IFR and EG is 3: 1 and the total amount of flame retardant added is 40 phr,the limiting oxygen index of the composite material reaches to 30.4%,meanwhile,the vertical burning test can pass the V-0 rating.Cone calorimetry tests showed that the peak heat release rate,total heat release,and total smoke production of EPDM/IFR/EG composites decreased by 69.05%,33.3%,and 57.8%,respectively.In addition,the flame retardance mechanism of IFR and EG in EPDM materials was analyzed by SEM,FTIR,TG-FTIR and XPS.The results showed that IFR and EG played flame retardancy in both gas and solid phases.At the same time,when IFR and EG were used in combination,no new chemical bond appeared,indicating that only physical synergy effect exists between them in the solid phase.Secondly,ceramicizable EPDM composite were prepared with glass powder(GP)as flux,mica(MP)and montmorillonite(MMT)as ceramic fillers,and fumed silica as reinforcing agents.The effects of ceramic component on the flame retardancy,mechanical properties and ceramic properties of EPDM were studied.The results show that the ceramic component improves the mechanical properties and flame retardancy of EPDM.When the content of silica,GP,MP and MMT are 30 phr,25.7 phr,34.3 phr and 10 phr respectively,the limiting oxygen index of the composites is 22.4%.The tensile strength and the elongation at break are 12.2 MPa and 427.5%,respectively.The three-point bending strength test results of the ceramics show that the ratio of GP and MP is the main factor affecting the ceramic properties of EPDM materials.And,when the ratio of GP and MP is 5: 2 and the total amount of ceramic component is 60 phr,the three-point bending strength of the composite material reaches to 17.5 MPa.Finally,ithe intumescent flame retardant and ceramic component were added together to EPDM to prepare ceramicizable intumescent flame retardant EPDM composites.The effects of the two components on the performance of EPDM composites were studied.The results show that the addition of ceramic component has a certain negative impact on the flame retardancy of EPDM composites.And the mechanical properties and combustion behavior have been improved with addition of the ceramic component.In addition,the three-point bending strength test results of the ceramics shows that the three-point bending strength of the ceramic bodies formed by the ceramicizable intumescent flame retardant EPDM composites is poor.