3-Mercaptobutanoic acid (3-MBA) was synthesized by the less odorous Michael addition pathway using an isothiouronium salt intermediate. Using the synthesized 3-MBA, multifunctional secondary thiol (sec-thiol) compounds were obtained and applied to thiol–epoxy curing systems as hardeners. As the functionality of the sec-thiol hardeners increased, the purity of the product obtained after distillation decreased. The equivalent epoxy mixtures with multifunctional sec-thiol hardeners were evaluated based on their impact on the curing behavior in thiol–epoxy click reactions by differential scanning calorimetry. The thermal features of sec-thiol–epoxy click reactions in the presence of a base catalyst were assessed according to the functionality of the sec-thiol hardeners. Our results showed that sec-thiol hardeners with less reactivity to the epoxy group provide long-term storage stability for the formulated epoxy resin, promising for industrial applications.

中文翻译：

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使用 3-巯基丁酸的多功能二级硫醇固化剂的合成和表征及其硫醇-环氧固化行为

3-巯基丁酸 (3-MBA) 是使用异硫脲盐中间体通过气味较小的迈克尔加成途径合成的。使用合成的 3-MBA，获得了多功能仲硫醇 ( sec -thiol) 化合物，并将其作为固化剂应用于硫醇-环氧树脂固化体系。随着仲硫醇硬化剂官能度的增加，蒸馏后得到的产品纯度降低。通过差示扫描量热法，基于它们对硫醇-环氧树脂点击反应中固化行为的影响，评估了具有多功能仲硫醇硬化剂的等效环氧混合物。sec的热特性根据仲硫醇硬化剂的功能评估在碱催化剂存在下的硫醇-环氧点击反应。我们的研究结果表明，对环氧基团反应性较低的仲硫醇固化剂为配制的环氧树脂提供了长期的储存稳定性，在工业应用方面很有前景。