不饱和型降冰片烯-三元乙丙橡胶的交联机理

Crosslinking Mechanism of Unsaturated Norbornene-EPDM Rubber

通过原位升温红外光谱结合差示扫描量热(DSC)测试,研究了ENB-EPDM的交联反应过程。从外扰相关移动窗口二位相关红外(PCMW2D)图谱和DSC曲线分析中可以观察到,交联反应的最大速率出现在178℃处。利用PCMW2D得到交联过程的反应温度区域在160~192℃。为了获得ENB-EPDM在交联反应过程中具体的交联机理,在广义二维相关分析中对相应官能团对应的波数进行分析。从各个官能团运动的先后次序上能够将这一交联过程划分为4个具体步骤,同时,环上双键的变化作为与交联过程平行的1个过程:过氧化二异丙苯(DCP)开始分解并释放出自由基;在主链亚甲基上的1个氢原子受到由DCP分解而来的自由基的进攻,从而形成一部分甲基自由基;由DCP分解而来的自由基在侧链甲基上进行自由基加成反应,生成新的链自由基;不同分子链之间的2个链自由基相互偶合生成新的共价键完成整个交联反应过程。与此同时,第3单体上的-CH-CH-结构在初始的游离过氧化自由基的诱发下,在热作用下脱氢形成双键,并在更高的温度下打开双键进行交联。

The cross-linking reaction process of ENB-EPDM was studied by in-situ heating infrared spectroscopy combined with DSC.From the analysis of perturbation-correlation moving-window two-dimensional correlation spectroscopy(PCMW2 D)spectrum and DSC,it can be observed that the maximum rate of the cross-linking reaction occurs at 178℃.By PCMW2 D,the reaction temperature range of the cross-linking process is 160~192℃.In order to obtain the specific cross-linking mechanism of ENB-EPDM in the cross-linking reaction process,the wave numbers corresponding to the corresponding functional group were analyzed in the generalized two-dimensional correlation.The cross-linking process can be divided into four specific steps from the sequence of movement of each functional group:DCP begins to decompose and release free radicals;a hydrogen atom on the main chain methylene groups is attacked by free radicals decomposed by DCP to form a part of methyl radicals;the free radicals decomposed by DCP undergo a radical addition reaction on the side chain methyl groups,generate new chain radicals;two chain radicals between different molecular chains couple with each other to produce new covalent bonds to complete the entire cross-linking reaction process.At the same time,the-CH-CH-structure on the third monomer is induced by the initial free peroxide radicals to form double bonds by dehydrogenation under the action of heat,and opens the double bonds at a higher temperature for cross-linking.