Abstract EPDM rubber gaskets, as a water-proof sealing material installed in the tunnel segment joints, were subjected to compressive stress-thermo oxidative ageing at different temperature and compressive stress levels. It was found that compared with thermo-oxidative ageing, compressive stress-thermo oxidative ageing of EPDM samples was more aggressive due to the destructive effect of compressive stress: the molecular structure was oxidized to form oxygenated species such as carbonyl groups, while high compressive stress level resulted in the degradation of EPDM with lower degradation activation energy ( E a ), and the breakage of CB network structure and phase separation. Meanwhile, the crosslinking reaction dominated over the chain scission reaction especially at high temperature during the whole ageing process, leading to the increase of crosslinking density of EPDM samples. With increasing ageing temperature and compressive stress, the ageing degree of EPDM rubber was much severe, and compressive stress promoted the degradation of samples, resulting in the decrease of glass transition temperature (Tg) and increase of free volume at high stress levels, while thermo-oxidative ageing promoted the crosslinking reaction of samples, leading to the higher Tg and lower free volume at high ageing temperature. As a result, the surface of EPDM rubber became much rough and interfacial debonding occurred between CB and EPDM matrix, while the mechanical and durable sealing resilience performance were deteriorated during stress-thermal ageing.

中文翻译：

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用于密封回弹评估的三元乙丙橡胶垫片的压缩应力-热氧化老化行为及机理

摘要 三元乙丙橡胶垫片作为安装在隧道管片接头上的防水密封材料，在不同温度和压应力水平下经受压应力-热氧化老化。结果发现，与热氧化老化相比，EPDM样品的压缩应力-热氧化老化由于压缩应力的破坏作用更具侵略性：分子结构被氧化形成羰基等氧化物质，而高压缩应力水平导致具有较低降解活化能 (E a ) 的 EPDM 降解，以及 CB 网络结构的破坏和相分离。同时，在整个老化过程中，交联反应主导了断链反应，尤其是在高温下，导致 EPDM 样品的交联密度增加。随着老化温度和压应力的增加，三元乙丙橡胶的老化程度越来越严重，压应力促进了样品的降解，导致玻璃化转变温度（Tg）降低，在高应力水平下自由体积增加，而热-氧化老化促进了样品的交联反应，导致在高老化温度下具有较高的 Tg 和较低的自由体积。结果，三元乙丙橡胶表面变得更加粗糙，CB和三元乙丙橡胶基体之间发生界面脱粘，而在应力-热老化过程中机械和耐用的密封回弹性能恶化。三元乙丙橡胶的老化程度非常严重，压应力促进了样品的降解，导致玻璃化转变温度（Tg）降低，在高应力水平下自由体积增加，而热氧化老化促进了样品的交联反应。样品，导致在高老化温度下更高的 Tg 和更低的自由体积。结果，三元乙丙橡胶表面变得更加粗糙，CB和三元乙丙橡胶基体之间发生界面脱粘，而在应力-热老化过程中机械和耐用的密封回弹性能恶化。三元乙丙橡胶的老化程度非常严重，压应力促进了样品的降解，导致玻璃化转变温度（Tg）降低，在高应力水平下自由体积增加，而热氧化老化促进了样品的交联反应。样品，导致在高老化温度下更高的 Tg 和更低的自由体积。结果，三元乙丙橡胶表面变得更加粗糙，CB和三元乙丙橡胶基体之间发生界面脱粘，而在应力-热老化过程中机械和耐用的密封回弹性能恶化。而热氧化老化促进了样品的交联反应，导致在高老化温度下具有较高的 Tg 和较低的自由体积。结果，三元乙丙橡胶表面变得更加粗糙，CB和三元乙丙橡胶基体之间发生界面脱粘，而在应力-热老化过程中机械和耐用的密封回弹性能恶化。而热氧化老化促进了样品的交联反应，导致在高老化温度下具有较高的 Tg 和较低的自由体积。结果，三元乙丙橡胶表面变得更加粗糙，CB和三元乙丙橡胶基体之间发生界面脱粘，而在应力-热老化过程中机械和耐用的密封回弹性能恶化。