Condensed tannins extracted from the Pinus radiata bark (PRTs) were used as a replacement for phenol in the synthesis of resol-type phenolic resins (FRs) and tested as polymer matrix in carbon nanofiber (CNF)-reinforced composite materials. The PRTs used herein contained a phenol and lignin content of 31 (Eq/L) and 35 (%w/w), respectively. The molecular weights of these polyphenols indicated the presence of 16 flavonoid units. Tannin resins were synthesized, and their characteristics were compared with those of the synthesized FRs using a formaldehyde/phenol ratio of (1.6/1.0), which has the highest total solids content. The results showed that the gel time and useful life of the resins decreased with the addition of the tannins, while there was no significant variation in the degradation temperature with varying FR contents. The mechanical properties of the CNF-reinforced composite materials were determined by DMA, and the results showed an increase of 1000 MPa, due to the better distribution of the fibers in the matrix. The modulus (E') in the reinforced composite materials with tannin resins was 2322 MPa and 1803 MPa without tannins, while modulus E¨ for composite materials doubled for resins with tannins. Tannins improved the dispersion of CNTs and the matrix-filled interface.

中文翻译：

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从辐射松树皮中提取的缩合单宁树脂作为碳纳米纤维增强聚合物中的支撑基质

从辐射松树皮 (PRT) 中提取的缩合单宁被用作合成甲阶酚醛树脂 (FR) 中苯酚的替代品，并在碳纳米纤维 (CNF) 增强复合材料中作为聚合物基质进行测试。此处使用的 PRT 包含的苯酚和木质素含量分别为 31 (Eq/L) 和 35 (%w/w)。这些多酚的分子量表明存在 16 个类黄酮单元。合成了单宁树脂，并将它们的特性与使用具有最高总固体含量的甲醛/苯酚比率 (1.6/1.0) 合成的 FRs 的特性进行了比较。结果表明，树脂的凝胶时间和使用寿命随着单宁酸的加入而降低，而降解温度随​​着阻燃剂含量的变化没有显着变化。CNF 增强复合材料的力学性能通过 DMA 测定，结果显示增加 1000 MPa，这是由于纤维在基体中的更好分布。含单宁树脂的增强复合材料的模量 (E') 为 2322 MPa 和不含单宁的 1803 MPa，而含单宁树脂的复合材料的模量 E¨ 增加了一倍。单宁改善了碳纳米管的分散和基质填充界面。