在模拟隧道地层环境介质中三元乙丙橡胶密封条老化行为和老化机理的研究

Study on Aging Behavior and Mechanism of EPDM Seals in Simulated Environment Medium of Tunnel Strata

探讨三元乙丙橡胶(EPDM)密封条在模拟隧道地层环境介质浓度为1mol·L^(-1)(1M)离子溶液中的老化行为和老化机理,并与其在蒸馏水中的老化行为和老化机理进行对比。结果表明:随着老化时间的延长,在两种介质中浸泡的EPDM密封条的硬度和压缩强度呈提高趋势,拉伸强度呈先下降后提高趋势,拉断伸长率和压缩永久变形呈减小趋势,应力松弛因数呈增大趋势,这是因为老化初期介质中的水分子在EPDM基体内渗透、扩散,导致补强剂的补强效果减弱,老化中后期吸水达到平衡,且发生后交联反应;相对质量变化率和相对吸水率先增大后减小;玻璃化温度(T_g)先下降后上升。EPDM密封条表面在老化过程中逐渐变粗糙,分离出固体颗粒物;在1M离子溶液中的老化速率略高于在蒸馏水中的老化速率。在蒸馏水中浸泡的EPDM密封条相对质量变化率和相对吸水率明显大于在1M离子溶液中浸泡的EPDM密封条,这与其吸水率大有关。在同一老化时间下,在1M离子溶液中浸泡的EPDM密封条的储能模量大于在蒸馏水老化中浸泡的EPDM密封条,T_g较低。

The aging behavior and mechanism of ethylene-propylene-diene rubber(EPDM) seal in the simulated environment medium of tunnel strata with the ionic solution having a concentration of 1 mol·L^-1(1M) were investigated and compared with the aging in distilled water. The results showed that the hardness and compressive strength of EPDM seals soaked in both media increased with the aging time,the tensile strength decreased first and then increased,the elongation at break and permanent compression set were reduced,and the stress relaxation coefficient was improved. The permeation and diffusion of water molecules from the media into the EPDM matrix at the initial stage of aging weakened the reinforcing effect of reinforcing agent. The water absorption gradually reached equilibrium and then crosslinking reaction occurred. The relative mass change rate and relative water absorption rate of EPDM seals increased first and then decreased,while glass transition temperature(Tg) showed a trend of first declining and then rising. The surface of EPDM seal gradually became rough during aging,and solid particles were separated out. The aging rate of EPDM seal soaked in 1M ionic solution was slightly higher than that soaked in distilled water. The relative mass change rate and relative water absorption rate of EPDM seals soaked in distilled water were obviously higher than those soaked in 1M ionic solution,which was related to their high water absorption rate. At the same aging time,the storage modulus of EPDM seals soaked in 1M ionic solution was larger than those soaked in distilled water,while the Tg was lower.