饱和型乙烯-丁烯弹性体的交联机理

Crosslinking Mechanism of Saturated Ethylene-Butene Elastomer

乙烯-丁烯共聚物弹性体(POE)通常采用过氧化二异丙苯(DCP)进行交联反应,但是该交联反应的具体机理尚不明确。文中通过原位升温红外光谱结合外扰相关移动窗口二维相关红外(PCMW2D)和广义二维相关红外分析对POE的DCP交联机理进行了分析。在差示扫描量热分析(DSC)中,POE交联反应过程的温度区域能够在曲线中得到佐证。从PCMW2D图谱分析和DSC曲线中可以看出,交联反应的最大速率出现在170~188℃处。为了获得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:DCP开始分解并释放出自由基;由DCP分解而来的自由基在主链亚甲基上进行自由基加成反应,生成新的链自由基;在侧链甲基上的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;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。

Dicumyl peroxide(DCP)was usually used for the cross-linking reaction of ethylene-butene copolymer elastomer(POE).However,the specific cross-linking reaction mechanism is not clear.In this article,the in-situ heating infrared spectroscopy was combined with the perturbation-correlation moving-window two-dimensional correlation spectroscopy(PCMW2D)and generalized two-dimensional correlation infrared analysis to analyze the DCP crosslinking mechanism of POE.Through DSC,the temperature ranges of the POE crosslinking reaction process can be confirmed.It can be seen from the PCMW2D spectra and DSC curve that the maximum rate of the crosslinking reaction occurs at 170~188℃.In order to obtain the specific cross-linking mechanism during the cross-linking reaction,the wavenumbers corresponding to the functional groups were analyzed by the generalized two-dimensional correlation analysis.From the sequence of movement of each functional group,the crosslinking process can be divided into four specific steps:DCP begins to decompose and release free radicals;free radicals decomposed by DCP are added to the main chain methylene groups,to generate new chain radicals;a hydrogen atom on the side chain methyl is attacked by the free radicals decomposed by DCP to form a part of methyl radicals;the radicals between different molecular chains couple with each other to produce new covalent bonds to complete the entire cross-linking reaction process.