Lanthanide–imidazole complexes as latent curing agents for epoxy resins
Lanthanide–imidazole complexes as latent curing agents for epoxy resins
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DOI：
10.1002/pola.1990.080280404
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发表时间：
1990-03
期刊：
影响因子：
--
通讯作者：
M. Kaplan;A. Wayda;A. Lyons
中科院分区：
文献类型：
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作者：
M. Kaplan;A. Wayda;A. Lyons
一段时间以来，咪唑被认为是环氧树脂的固化剂。一旦树脂和咪唑化合物混合，则该混合物可以使用的时间相对较短，因为即使在室温下也会发生一定程度的聚合(固化)反应，导致反应混合物变稠。为了解决这个问题，我们发现咪唑可以与有机镧系化合物络合，从而束缚咪唑并延迟其在环境温度下环氧材料固化中的反应速率。当需要提高固化速率时，只需升高混合物的温度即可。本文涉及 M(THD)3-IM 系列的环氧树脂固化反应的研究。 M表示镧系金属Eu、Ho、Pr、Dy、Yb和Gd，THD是2,2,6,6-四甲基-3,5-庚二酮。固化反应之后进行差示扫描量热法，并且在某些情况下通过红外光谱法。我们已经证明这些有机镧系元素-咪唑配合物是环氧树脂的有效热潜固化剂。在 150°C 的温度下，固化速度相当快。在这些研究过程中，还确定了络合物中的镧系元素离子半径与固化反应发生的温度之间存在反比关系。因此，Yb 化合物（其中咪唑结合最强）在最高温度下固化，而 Pr（其中咪唑结合最弱）在最低温度下固化。与这些事实一致的是，Yb 化合物与环氧树脂混合时也给出了最长的潜伏期。
Imidazoles have for some time been recognized as curing agents for epoxy resins. Once the resin and the imidazole compound are mixed there is a relatively short time in which the mixture can be used, since the polymerization (curing) reaction occurs to some extent even at room temperature causing the reaction mixture to thicken. In order to circumvent this problem we have found that imidazoles can be complexed with organo-lanthanide compounds thereby tying up the imidazole and retarding its rate of reaction in the cure of epoxy materials at ambient temperatures. When it is desired to enhance the rate of cure the temperature of the mixture is simply raised. This paper concerns studies of the epoxy cure reaction with the M(THD)3–IM series. M represents the lanthanide metals Eu, Ho, Pr, Dy, Yb, and Gd, and THD is 2,2,6,6-tetramethyl-3,5-heptanedione. Cure reactions were followed by differential scanning calorimetry and in some cases by infrared spectroscopy. We have demonstrated that these organo-lanthanide–imidazole complexes are effective thermally latent curing agents for epoxy resins. At a temperature of 150°C cure is quite rapid. In the course of these studies it has also been determined that there is an inverse correlation between the lanthanide ionic radius in the complex and the temperature at which the cure reaction occurs. Thus the Yb compound, where the imidazole is most strongly bound, cures at the highest temperature and Pr, where imidazole is bound most weakly, at the lowest. Consistent with these facts is the observation that the Yb compound also gives the longest latency period when mixed with epoxy resin.