Study On The Aging Mechanism Of EPDM In Pem Fuel Cell Environment

The sealing performance of the proton exchange membrane(PEM)fuel cell plays a vital role for the safety of the fuel cell,and the effective sealing performance depends on the stability of the sealing material.Ethylene-propylene-diene rubber(EPDM)can be used as the sealing material in PEM fuel cell because of its good sealing performance.However,the interior of the PEM fuel cell is high temperature and acidic environment,and the rubber will inevitably degrade when it works here for long time.In order to improve the stability of EPDM in high temperature and acid environment,we first need to understand the degradation mechanism of rubber.Therefore,this paper carried out the degradation experiment of EPDM in the simulated PEM fuel cell environment,and explored the aging phenomenon and aging mechanism of EPDM in standard solution(RS)and accelerated durability test(ADT)from the following aspects:(1)The degradation experiment of peroxide-cured EPDM in RS and ADT was studied and found that the EPDM in both RS and ADT environment were all degraded.In the early stage of aging,the oxidative cracking occurred in the the main molecular chain and ENB crosslinking point of EPDM,and generating double bonds and oxygen-containing substances,which destroyed the crosslinking network of rubber and damaged its mechanical properties.In the later stage of aging,a crosslinking reaction occurred in EPDM when it was aged in RS,which repaired the crosslinking network and improved the mechanical properties.However,no crosslinking reaction occurred when EPDM was aged in ADT,but its overall aging degree is still lower than that aged in RS,indicating that the stability of peroxide-cured EPDM in ADT was higher than that in RS;(2)The degradation of sulfur-cured EPDM in RS and ADT was studied and found that when the rubber was aging,the sulfur and polysulfide will react with ENB or double bonds that produced by the aging of EPDM under the action of the remaining accelerator and accelerator pendant group to produce the sulfur crosslinking structure,and the sulfur crosslinking structure was dominated by polysulfide bonds,which made the aged EPDM became hard and brittle;(3)The degradation of EPDM that containing TAIC crosslinking point in RS and ADT was studied and found that EPDM showed different changes in the two environments: the EPDM that was aged in RS had underwent a hydrolysis reaction of TAIC crosslinking points and a cleavage reaction of the molecular main chain,which seriously damaged the performance of rubber;while when the EPDM was aged in ADT,only a hydrolysis reaction of TAIC crosslinking points had occurred,which improved the stability of the rubber.