Shi Kang, Liu Guoshuai, Sun Hui, Yang Biao, Weng Yunxuan
College of Chemistry and Materials Engineering, Beijing Technology and Business University, Beijing 100048, China.
Beijing Key Laboratory of Quality Evaluation Technology for Hygiene and Safety of Plastics, Beijing Technology and Business University, Beijing 100048, China.
ACS Omega. 2023 Jul 23;8(30):26926-26937. doi: 10.1021/acsomega.3c01738. eCollection 2023 Aug 1.
The development of low-cost and high-performance bio-based composites derived from forestry waste lignin and polylactic acid has emerged as a topic of central attention. However, the weak compatibility between lignin and polylactic acid often resulted in high brittleness of the composites. Graft copolymerization is not only the most effective way to modify lignin but also can significantly improve the compatibility of lignin and polylactic acid. In this study, bio-based monomer lauryl methacrylate was grafted onto lignin by feasible radical polymerization to prepare lignin graft copolymers with excellent thermal stability and hydrophobicity, which are expected to improve the compatibility with polylactic acid. Wholly bio-based composites were prepared by compounding this graft copolymer with polylactic acid. The results showed that the crystallization ability of the composite was improved, and the highest crystallinity was increased from 6.42% to 17.46%. With addition of LG-g-PLMA lower than 9%, the thermal stability of the composites was slightly improved. At 5% copolymer addition, the elongation at break and tensile toughness of the composites increased by 42% and 36%, respectively. Observation of the frozen fracture surface of the composite by SEM found that wire drawing and ductile deformation appeared when a small amount of LG-g-PLMA was added. The thus prepared composites also showed excellent UV barrier properties. This approach provides a new idea for the high-value application of lignin.
利用林业废弃物木质素和聚乳酸制备低成本、高性能生物基复合材料已成为备受关注的核心课题。然而，木质素与聚乳酸之间较弱的相容性常常导致复合材料具有高脆性。接枝共聚不仅是改性木质素的最有效方法，而且能显著提高木质素与聚乳酸的相容性。本研究通过可行的自由基聚合反应将生物基单体甲基丙烯酸月桂酯接枝到木质素上，制备出具有优异热稳定性和疏水性的木质素接枝共聚物，有望改善其与聚乳酸的相容性。将该接枝共聚物与聚乳酸共混制备全生物基复合材料。结果表明，复合材料的结晶能力得到提高，最高结晶度从6.42%提高到17.46%。当LG-g-PLMA添加量低于9%时，复合材料的热稳定性略有提高。当共聚物添加量为5%时，复合材料的断裂伸长率和拉伸韧性分别提高了42%和36%。通过扫描电子显微镜观察复合材料的冷冻断面发现，添加少量LG-g-PLMA时出现拉丝和韧性变形现象。所制备的复合材料还表现出优异的紫外线阻隔性能。该方法为木质素的高值化利用提供了新思路。
