Yoo Heesu, Jo Jaemin, Kim Sung Jin, Koo Bonwook
Major in Wood and Paper Science, School of Forestry, Science and Landscape Architecture, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea.
Institute of Agricultural Science and Technology, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, Republic of Korea.
Polymers (Basel). 2025 Jun 20;17(13):1727. doi: 10.3390/polym17131727.
The global market for flame-retardant materials is expected to grow steadily, from USD 7.0 billion in 2022 to USD 16.6 billion in 2030, driven by increasing demand for environment-friendly fire safety solutions in transportation, construction, and electronics. Polylactic acid (PLA), a biodegradable polymer which possesses excellent mechanical properties, is increasingly being considered for future mobility applications. However, it is characterized by high heat release and toxic smoke during combustion, which are significant drawbacks. In order to address this, the chemical modification of Kraft lignin was achieved through a phenolation and subsequent silylation with tetraethoxysilane, aiming to mitigate the degradation of PLA's mechanical properties while utilizing its inherent char-forming ability. The modified lignins were combined with ammonium polyphosphate (APP) and melt-mixed with PLA using an injection-mixing molder to prepare test specimens. Analysis by FT-IR, NMR spectroscopy, and SEM-EDS confirmed successful grafting of phenolic and silane functionalities, and thermogravimetric analysis demonstrated enhanced thermal stability of the modified lignins compared to unmodified ones. Vertical burning tests and limiting oxygen index (LOI) measurements showed that the PLA/APP/SPKL composite material achieved a V-0 UL-94 rating and 31.95% LOI, demonstrating the highest level of flame retardancy. This compares to the LOI of neat PLA, 19 to 21%. Despite the enhancement in flame retardancy to the V-0 level, the decline in tensile strength was limited, and the composite retained comparable mechanical strength to PLA-APP composites with V-2 flame retardancy. The findings indicate that the combination of phenolation and silylation of lignin with APP, a flame-retardant material, offers a viable and sustainable methodology for the fabrication of PLA composites that exhibit both flame retardancy and mechanical strength.
受交通运输、建筑和电子领域对环保消防安全解决方案需求不断增长的推动，全球阻燃材料市场预计将稳步增长，从2022年的70亿美元增长到2030年的166亿美元。聚乳酸（PLA）是一种具有优异机械性能的可生物降解聚合物，越来越多地被考虑用于未来的移动应用。然而，它的特点是燃烧时热释放高且产生有毒烟雾，这是显著的缺点。为了解决这个问题，通过酚化以及随后用四乙氧基硅烷进行硅烷化实现了对硫酸盐木质素的化学改性，旨在在利用其固有的成炭能力的同时减轻PLA机械性能的降解。将改性木质素与聚磷酸铵（APP）混合，并使用注塑混合成型机与PLA进行熔融共混以制备测试样品。通过傅里叶变换红外光谱（FT-IR）、核磁共振光谱（NMR）和扫描电子显微镜-能谱分析（SEM-EDS）证实了酚基和硅烷官能团的成功接枝，热重分析表明改性木质素与未改性木质素相比具有更高的热稳定性。垂直燃烧试验和极限氧指数（LOI）测量表明，PLA/APP/SPKL复合材料达到了UL-94 V-0等级和31.95%的LOI，显示出最高水平的阻燃性。相比之下，纯PLA的LOI为19%至21%。尽管阻燃性提高到了V-0等级，但拉伸强度的下降有限，该复合材料保留了与具有V-2阻燃性的PLA-APP复合材料相当的机械强度。研究结果表明，木质素的酚化和硅烷化与阻燃材料APP相结合，为制备兼具阻燃性和机械强度的PLA复合材料提供了一种可行且可持续的方法。
