Fei Xiaoma, Zhao Fangqiao, Wei Wei, Luo Jing, Chen Mingqing, Liu Xiaoya
The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, China.
Polymers (Basel). 2016 Aug 26;8(9):314. doi: 10.3390/polym8090314.
Toughening an epoxy resin by bio-based modifiers without trade-offs in its modulus, mechanical strength, and other properties is still a big challenge. This paper presents an approach to modify epoxy resin with tannic acid (TA) as a bio-based feedstock. Carboxylic acid-modified tannic acid (TA⁻COOH) was first prepared through a simple esterification between TA and methylhexahydrophthalic anhydride, and then used as a modifier for the epoxy/anhydride curing system. Owing to the chemical modification, TA⁻COOH could easily disperse in epoxy resin and showed adequate interface interaction between TA⁻COOH and epoxy matrix, in avoid of phase separation. The use of TA⁻COOH in different proportions as modifier of epoxy/anhydride thermosets was studied. The results showed that TA⁻COOH could significantly improve the toughness with a great increase in impact strength under a low loading amount. Moreover, the addition of TA⁻COOH also simultaneously improved the tensile strength, elongation at break and glass transition temperature. The toughening and reinforcing mechanism was studied by scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA), which should be owned to the synergistic effect of good interface interaction, aromatic structure, decreasing of cross linking density and increasing of free volume. This approach allows us to utilize the renewable tannic acid as an effective modifier for epoxy resin with good mechanical and thermal properties.
使用生物基改性剂增强环氧树脂，同时不牺牲其模量、机械强度和其他性能，仍然是一个巨大的挑战。本文提出了一种以单宁酸（TA）作为生物基原料来改性环氧树脂的方法。首先通过TA与甲基六氢邻苯二甲酸酐之间的简单酯化反应制备了羧酸改性单宁酸（TA⁻COOH），然后将其用作环氧/酸酐固化体系的改性剂。由于化学改性，TA⁻COOH能够轻松分散在环氧树脂中，并在TA⁻COOH与环氧基体之间表现出足够的界面相互作用，避免了相分离。研究了使用不同比例的TA⁻COOH作为环氧/酸酐热固性材料改性剂的情况。结果表明，TA⁻COOH在低负载量下能显著提高韧性，冲击强度大幅增加。此外，添加TA⁻COOH还同时提高了拉伸强度、断裂伸长率和玻璃化转变温度。通过扫描电子显微镜（SEM）、动态力学分析（DMA）和热机械分析（TMA）研究了增韧和增强机理，这应归功于良好的界面相互作用、芳香结构、交联密度降低和自由体积增加的协同效应。这种方法使我们能够将可再生的单宁酸用作具有良好机械和热性能的环氧树脂有效改性剂。
