Wu Miao, Peng Jian-Jun, Dong You-Ming, Pang Jin-Hui, Zhang Xue-Ming
National Engineering Laboratory for Pulp and Paper, China National Pulp and Paper Research Institute Co. Ltd Beijing 100102 China
Key Laboratory of Pulp and Paper Science & Technology of Ministry of Education, Qilu University of Technology (Shandong Academy of Sciences) Jinan 250353 China.
RSC Adv. 2022 Aug 5;12(34):21736-21741. doi: 10.1039/d2ra02895f. eCollection 2022 Aug 4.
Lignin, one of the main components of lignocellulose, can be used as an alternative to chemical polyols in the production of polyurethane because of its abundant phenolic and alcohol hydroxyls. Traditionally, lignin is directly applied in the preparation of polyurethane; however, modified lignin has been proved to be superior, especially that obtained by the oxypropylation reaction. Therefore, lignopolyol obtained by mild and efficient oxypropylation was utilized in the production of rigid polyurethane foam in this study. Specifically, the effects of the content of lignopolyol on the chemical structure, morphological structure, mechanical properties and thermal stability of the lignin-based rigid polyurethane foam were investigated. It was found that the compressive strength of the rigid polyurethane foam was significantly improved with the addition of lignopolyol compared with that of the pure polyurethane foam, which was attributed to the fact that oxypropylation made lignin into highly branched and functionalized polyols by transforming all phenolic hydroxyls into aliphatic hydroxyls. Moreover, when the molal weight of lignopolyol accounted for 40% of the added polyols, the generated foam showed optimal uniformity and regularity, and the compressive strength reached 0.18 MPa, meeting the requirements of industrial application, below which, the amount of undesired reactions is bound to increase. As a consequence, the added amount of lignopolyol was increased as much as possible on the basis of guaranteeing the desired properties, which was more conducive to realizing the green degradation and economic synthesis of rigid polyurethane foam.
木质素是木质纤维素的主要成分之一，由于其含有丰富的酚羟基和醇羟基，可在聚氨酯生产中用作化学多元醇的替代品。传统上，木质素直接用于聚氨酯的制备；然而，已证明改性木质素更具优势，尤其是通过氧丙基化反应获得的木质素。因此，本研究采用温和高效的氧丙基化反应制得的木质素多元醇来生产硬质聚氨酯泡沫。具体而言，研究了木质素多元醇含量对木质素基硬质聚氨酯泡沫的化学结构、形态结构、力学性能和热稳定性的影响。结果发现，与纯聚氨酯泡沫相比，添加木质素多元醇后硬质聚氨酯泡沫的抗压强度显著提高，这归因于氧丙基化反应通过将所有酚羟基转化为脂肪族羟基，使木质素变成高度支化且功能化的多元醇。此外，当木质素多元醇的摩尔质量占所添加多元醇的40%时，所制得的泡沫具有最佳的均匀性和规整性，抗压强度达到0.18MPa，满足工业应用要求，低于该比例，不期望发生的反应量必然增加。因此，在保证所需性能的基础上，应尽可能增加木质素多元醇的添加量，这更有利于实现硬质聚氨酯泡沫的绿色降解和经济合成。
