High-Strength Carbon Fibers from Eco-Friendly Processing of Biomass

来自生物质环保加工的高强度碳纤维

• 批准号: 1462804
• 负责人: Amod Ogale
• 金额: $ 37.5万
• 依托单位: Clemson University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-15 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1462804&HistoricalAwards=false
• 关键词: Strength; Carbon; Fibers; Eco; Friendly

Carbon fibers are among the strongest known reinforcing fibers used in a wide range of commercial composite materials. Because the element carbon does not melt, carbon fibers need to be obtained from organic precursors. Among renewable feedstocks, lignin is starting to play an important role as a potential precursor for carbon fibers, owing to its significant carbon content. However, the irregular chemical architecture of lignin makes the resulting carbon network very inefficient. Therefore, the resulting carbon-fiber properties are still significantly lower than those obtained from currently used synthetic polyacrylonitrile precursor, which involves the use of strong solvents and leads to toxic off-gases such as hydrogen cyanide. This research project is directed towards the development of a green precursor and an efficient processing route to obtain high strength carbon fibers.Lignin is readily available as an inexpensive by-product from Kraft paper mills, but this untreated form contains too many impurities to be used in high-performance products such as carbon fibers. Recently, Clemson researchers have discovered a renewable solvent that can purify Kraft lignin and isolate a high molecular weight lignin fraction in the solvated state. Clemson researchers (in a separate project) have also shown that dry-spinning of non-fractionated, acetylated lignin can lead to carbon fibers with enhanced strength. Therefore, the research team hypothesizes that the solvated lignin precursor will enable direct dry-spinning of precursor fibers, followed by their conversion to microstructure-controlled, high-performance carbon fibers. The specific research objectives are (i) control of the molecular architecture of fractionated-solvated lignin precursors (ii) rheological evaluation of suitable solvated lignin fractions to measure strain-hardening for efficient dry-spinning of precursor fibers, and (iii) microstructural control to obtain superior performance in the resulting carbon fibers. The intellectual significance of this research is that lignin fractions with controlled molecular weight and architecture will provide a unique materials platform for studying the rheological and microstructural (rheo-structural) behavior of these bio-derived fluids. Specifically, a long-linear architecture will be identified that leads to strain-hardening during extensional flow, a desirable phenomenon for stable dry-spinning of fibers. It is hypothesized that the control of molecular architecture of the fractionated-solvated lignin will lead to the efficient formation of graphitic carbon and superior properties for the resulting carbon fibers.

碳纤维是广泛用于商业复合材料的已知最强的增强纤维之一。 由于碳元素不熔化，碳纤维需要从有机前体获得。在可再生原料中，木质素由于其显著的碳含量而开始作为碳纤维的潜在前体发挥重要作用。 然而，木质素的不规则化学结构使得所得碳网络非常低效。因此，所得的碳纤维性质仍然显著低于从目前使用的合成聚丙烯腈前体获得的那些碳纤维性质，合成聚丙烯腈前体涉及使用强溶剂并导致有毒废气如氰化氢。该研究项目旨在开发一种绿色前体和一种有效的工艺路线，以获得高强度碳纤维。木质素是牛皮纸米尔斯厂容易获得的廉价副产品，但这种未经处理的形式含有太多的杂质，无法用于高性能产品，如碳纤维。最近，克莱姆森研究人员发现了一种可再生溶剂，其可以纯化硫酸盐木质素并分离溶剂化状态的高分子量木质素级分。克莱姆森的研究人员（在一个单独的项目中）还表明，未经分级的乙酰化木质素的干纺可以导致碳纤维的强度增强。 因此，研究小组假设溶剂化木质素前体将使前体纤维能够直接干纺，然后将其转化为微观结构控制的高性能碳纤维。具体的研究目标是（i）控制分级溶剂化木质素前体的分子结构（ii）对合适的溶剂化木质素级分进行流变学评价以测量前体纤维的有效干纺的应变硬化，以及（iii）微观结构控制以获得所得碳纤维的上级性能。本研究的智力意义在于，具有受控分子量和结构的木质素级分将为研究这些生物衍生流体的流变学和微观结构（流变结构）行为提供独特的材料平台。具体而言，将确定一个长的线性架构，导致在拉伸流动过程中的应变硬化，稳定的干纺纤维的理想现象。据推测，分级溶剂化木质素的分子结构的控制将导致石墨碳的有效形成和所得碳纤维的上级性能。