Study On Heat-resistant Air Aging Property Of EPDM And Applicability Of Hyperelastic Model At High Temperature Field

In this paper,the high temperature tensile properties and heat-resistant air aging properties of EPDM were studied.At the same time,the high temperature tensile data of some formulations were selected and the constitutive model equations were fitted to the high temperature field.The extension behavior was evaluated.The similarities and differences between ethylene-octene copolymer(POE)and propylene-based elastomer(PBE)for blending and modifying EPDM were analyzed and compared.The results show that when vulcanized dicumyl peroxide(DCP)is used,the addition of POE will reduce the degree of vulcanization of the system,while the addition of PBE will increase the degree of vulcanization,and the aging resistance will be better with the increase of POE or PBE.The increase in the number of POE fractions increases the high temperature tensile strength of the compound.When sulfur vulcanization is used,the addition of POE or PBE will prolong the curing time of the process.The heatresistant air aging performance will increase with the increase of PBE fraction.The addition of POE or PBE will make the high-temperature tensile properties of the rubber compound first.After the deterioration,the EPDM/POE ratio of the highest tensile strength at high temperature was 60/40,and the ratio of EPDM/PBE was 80/20.The situation of ordinary sulfur and insoluble sulfur vulcanized EPDM was analyzed.It was found that the tensile strength and elongation at break of EPDM after hot air aging were lower than that of insoluble sulfur vulcanized EPDM when using ordinary sulfur vulcanized EPDM.In addition,its 50% stress at given elongation is a large increase when the amount of sulfur is 1 to 3,and the increase is more than 3.In the DCP vulcanization system,the similarities and differences between the use of TMTD as a co-crosslinking agent and sulfur were analyzed.It was found that TMTD would improve the vulcanization efficiency of EPDM,but the degree of vulcanization was significantly lower than when sulfur was used as a co-crosslinking agent,but after heat tthe cross-linking density of the vulcanizate using TMTD after air aging is less than that of sulfur.EPDM using TMTD is superior to sulfur in heat-resistant air aging,but the initial physical properties under normal conditions are poor.High temperature tensile properties EPDM using sulfur is better than TMTD,and the high temperature performance is not obvious with the different amount of TMTD,but the different amount of sulfur will cause significant fluctuations in the high temperature tensile properties of EPDM.The coincidence of the Mooney-Rivlin model and the Yeoh model with the high temperature tensile stress-strain curve of EPDM was investigated.The fitting data of the Mooney-Rivlin model was in good agreement with the actual data.The fitting data of the Mooney-Rivlin model in the initial stage and the late stage of stretching are lower than the experimental data.The fitting data of the Mooney-Rivlin model is higher than the experimental data in the middle of the stretching stage.The fitting curve of the Yeoh model revolves around the actual data fluctuation.The late tensile stage is generally higher than the actual data,and the best condition is obtained when the DCP dosage is 4 parts and the sulfur content is 1 part.In contrast,the Mooney-Rivlin model is generally better than the Yeoh model.