Irradiation effects on the relaxation behaviour of EPDM elastomers
Irradiation effects on the relaxation behaviour of EPDM elastomers
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DOI：
10.1002/pi.1425
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发表时间：
2004-05-01
影响因子：
3.2
通讯作者：
Seytre, G
中科院分区：
文献类型：
--
作者：
Celette, N;Stevenson, I;Seytre, G
为了改变三元乙丙橡胶的力学和介电性能，在氧化气氛下对三元乙丙橡胶进行了γ辐照。研究了三种不同配方的三元乙丙橡胶（70wt%乙烯，28wt%丙烯；二烯单体：2wt%降冰片烯）：非交联三元乙丙橡胶共聚物，交联三元乙丙橡胶和用抗氧化剂稳定的交联三元乙丙橡胶。介电弛豫和机械弛豫表现为-120度（1hz）的β -亚玻璃弛豫和-15度（1hz）的α -弛豫，这与玻璃化转变有关，但受辐照效应的影响。与β弛豫相关的局部迁移率仅受高达450 kGy的γ辐照的微弱影响。由于交联和半晶结构的变化，α过程转移到更高的温度。电介质α过程的振幅增加是由于氧化物质在氧照射下形成的结果。相反，由于物理和化学交联，机械α弛豫振幅减小。结果表明，决定三元乙丙橡胶材料交联/断链平衡的主要因素有：(1)氧的存在和辐照剂量；(2)剂量率；(3)初始交联密度。因此，交联和结晶的单独贡献，以及因此对γ辐照后性质的理解和预测，只能在比较聚合物在其熔化温度以下和高于其熔化温度的行为后推断出来。(C) 2004年化学工业学会。
gamma-irradiation of ethylene-propylene diene monomer (EPDM) elastomers under oxidant atmosphere was carried out in order to change their mechanical and dielectric behaviour. Three different formulations of EPDM (70wt% ethylene, 28wt% propylene; diene monomer: 2wt% norbornene) were studied: a non-crosslinked EPDM terpolymer, a crosslinked EPDM and a crosslinked EPDM stabilized with an antioxidant. Dielectric and mechanical relaxation show a beta-sub-glass relaxation at about -120degreesC (1 Hz) and an alpha-relaxation at -15 degreesC (1 Hz) associated with the glass transition but influenced by the effects of irradiation. The local mobility associated with the beta-relaxation is only weakly influenced by gamma-irradiation up to 450 kGy. The alpha-process is shifted to higher temperatures as a result of crosslinking and changes in the semicrystalline structure. The amplitude of the dielectric alpha-process increases as a result of the formation of oxidized species during irradiation under oxygen. In contrast, the mechanical alpha-relaxation amplitude decreases as a result of physical and chemical cross-linking. It was shown that the main factors that determine the crosslinking/chain scission balance are (1) the presence of oxygen together with the irradiation dose, (2) the dose rate and (3) the initial crosslink density of the EPDM material. As a result, the individual contribution of crosslinking and crystallization, and therefore the understanding and prediction of the properties after gamma-irradiation can only be deduced after comparison of the polymer behaviour below and above its melting temperature. (C) 2004 Society of Chemical Industry.