木质素催化固化苯并噁嗪及其产物热性能研究

以对甲酚-苯胺型苯并噁嗪为模型化合物，玉米秸秆木质素为固化催化剂，用¹H-NMR研究木质素催化苯并噁嗪的聚合机理。随后将木质素与双酚A-苯胺型苯并噁嗪共混，得到不同木质素质量分数（0、0.5%、1%、2%、5%）的共混体系。通过DSC研究了共混体系的固化行为，并用DMA、TGA对固化产物热性能进行测试。结果表明：在木质素催化作用下，苯并噁嗪首先开环聚合生成含苯氧结构和Mannich桥结构的中间体，而苯氧结构中间体不稳定，会重排生成Mannich桥结构的最终产物；木质素的引入显著降低了苯并噁嗪的固化温度，且随着木质素含量的增加，共混体系的起始固化温度和固化峰值温度均逐渐降低；与聚苯并噁嗪相比，共混体系固化产物的玻璃化转变温度升高，分解温度略有下降，800 ℃时的残炭率有所提高。

Mechanism of formation and thermal properties of benzoxazine/lignin resins

A p-cresol-aniline-based benzoxazine was synthesized as a model compound and the mechanism of its ring-opening polymerization mechanism with corn straw lignin as a catalyst was investigated by ¹H-NMR spectroscopy. Blends were prepared by mixing bisphenol A and lignin with different mass percentages of lignin（0, 0.5%，1%，2% and 5% mass fraction）. The curing behavior of mixtures was investigated by DSC and their thermal properties were studied by DMA and TGA. The results show that in the presence of lignin phenoxy and Mannich bridge structures are initially formed after ring-opening polymerization of benzoxazine, but the phenoxy units are less stable and are eventually transformed into Mannich bridge structures by rearrangement. The initiation and peak curing temperatures of the mixtures were lower than those of the pure benzoxazine monomers, and the temperatures decreased with increasing content of lignin in the mixture. The tg values and char yields at 800℃ of cured products of the mixtures were higher than the corresponding values for pure benzoxazine, while the decomposition temperature decreased slightly.