Lignin was modified by oxidation to prepare lignin-derived polycarboxylic acids (LPCAs). LPCAs can be introduced into rigid polyurethane foams (RPUFs) via 1,4-dioxane. The expansion ratio and compressive strength of RPUFs were observed. When the loading of LPCAs was 0.67 wt% (based on polyol), the compressive strength of RPUF was the highest and was about 59.2% higher than that of the blank RPUF. The reinforcing mechanism of LPCAs was supposed that the interactions between LPCAs and RPUFs increased the strength of the cell walls. When the loading of LPCAs was less than 0.33 wt%, the expansion ratio of RPUFs increased slightly. The water resistance of RPUFs was not affected by LPCAs, suggesting that RPUFs with LPCAs could be used in a humid environment. Besides, the application of the oxidative modification products of lignin was broadened.

中文翻译：

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木质素衍生的多元羧酸不同载量的硬质聚氨酯泡沫的制备与表征

通过氧化将木质素改性以制备木质素衍生的多元羧酸（LPCA）。LPCA可以通过1,4-二恶烷引入硬质聚氨酯泡沫（RPUF）中。观察了RPUF的膨胀率和抗压强度。当LPCA的负载量为0.67重量％（基于多元醇）时，RPUF的抗压强度最高，并且比空白RPUF的抗压强度高约59.2％。LPCA的增强机制被认为是LPCA和RPUF之间的相互作用增加了细胞壁的强度。当LPCA的负载量小于0.33wt％时，RPUF的膨胀率略有增加。RPUF的耐水性不受LPCA的影响，这表明带有LPCA的RPUF可以在潮湿的环境中使用。此外，拓宽了木质素氧化改性产物的应用范围。