二硫化四甲基秋兰姆对烯丙基环氧树脂的固化机理研究

采用差示扫描量热法（DSC）、红外光谱法（FT-IR）跟踪研究了二硫化四甲基秋兰姆(TMTD)对二烯丙基双酚A型环氧树脂(DADGEBA)的固化行为,结果表明体系在升温过程中有热量放出，且双键和环氧基团含量均随反应时间增加而减少。随后采用核磁（1H-NMR）和质谱（MS）表征了二烯丙基双酚(DABPA)/TMTD体系受热前后的结构变化，发现有巯基生成，并推测得到多种生成物结构。根据实验结果推测DADGEBA/TMTD体系固化机理为协同固化反应：首先TMTD在高温下裂解生成硫自由基；之后部分硫自由基夺取烯丙基α碳上的氢，形成巯基，同时自由基转移到烯丙基α碳上，部分硫自由基与双键进行加成反应；最后生成的巯基进一步与环氧基团发生开环固化反应，生成烯丙基α碳自由基偶合终止。

Curing mechanism of diallyl-bearing epoxy resin/tetramethylthiuram disulfide

The curing of the diglycidyl ether of 2,2′-diallyl bisphenol A (DADGEBA) with tetramethylthiuram disulfide (TMTD) has been investigated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). Exotherms were observed in DSC curves, and FT-IR measurements showed that the amounts of vinyl and epoxy groups decreased with increasing time when the DADGEBA/TMTD mixture was heated. 1H-NMR was adopted to monitor the mercapto groups in diallyl bisphenol A (DABPA)/TMTD reaction mixture. Mass spectroscopy was used to detect the molecular weight and the structures of the products formed. Based on the experimental results, it was concluded that the curing mechanism of DADGEBA/TMTD involves a synergistic curing reaction: first, TMTD can cleave into sulfur radicals at high temperature; then, the α-H of the allyl groups can be captured by some of the sulfur radicals to form mercapto groups and the radicals are transferred to allyl structures, and the other sulfur radicals initiate addition reactions of vinyl groups; finally, the resulting mercapto groups react further with epoxy groups through ring opening reactions. Meanwhile, coupling reactions also occur between different radicals.