Navarro Carlos A, Kedzie Elyse A, Ma Yijia, Michael Katelyn H, Nutt Steven R, Williams Travis J
Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, CA 90089-1661.
M.C. Gill Composites Center and Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089-0241.
Top Catal. 2018 Jun;61(7-8):704-709. doi: 10.1007/s11244-018-0917-2. Epub 2018 Mar 27.
Carbon fiber-reinforced polymer (CFRP) materials are widely used in aerospace and recreational equipment, but there is no efficient procedure for their end-of-life recycling. Ongoing work in the chemistry and engineering communities emphasizes recovering carbon fibers from such waste streams by dissolving or destroying the polymer binding. By contrast, our goal is to depolymerize amine-cured epoxy CFRP composites catalytically, thus enabling not only isolation of high-value carbon fibers, but simultaneously opening an approach to recovery of small molecule monomers that can be used to regenerate precursors to new composite resin. To do so will require understanding of the molecular mechanism(s) of such degradation sequences. Prior work has shown the utility of hydrogen peroxide as a reagent to affect epoxy matrix decomposition [1]. Herein we describe the chemical transformations involved in that sequence: the reaction proceeds by oxygen atom transfer to the polymer's linking aniline group, forming an -oxide intermediate. The polymer is then cleaved by an elimination and hydrolysis sequence. We find that elimination is the slower step. Scandium trichloride is an efficient catalyst for this step, reducing reaction time in homogeneous model systems and neat cured matrix blocks. The conditions can be applied to composed composite materials, from which pristine carbon fibers can be recovered.
碳纤维增强聚合物（CFRP）材料广泛应用于航空航天和娱乐设备，但目前尚无有效的报废回收方法。化学和工程领域正在进行的工作重点是通过溶解或破坏聚合物粘结剂，从这些废物流中回收碳纤维。相比之下，我们的目标是催化胺固化环氧CFRP复合材料解聚，这样不仅能够分离出高价值的碳纤维，同时还能开辟一种回收小分子单体的方法，这些单体可用于再生新复合树脂的前体。要实现这一目标，需要了解此类降解过程的分子机制。先前的工作表明，过氧化氢作为一种试剂可有效促进环氧基质分解[1]。在此，我们描述了该过程中涉及的化学转化：反应通过氧原子转移至聚合物的连接苯胺基团进行，形成一种氧化物中间体。然后，聚合物通过消除和水解过程裂解。我们发现消除过程是较慢的步骤。三氯化钪是该步骤的有效催化剂，可缩短均相模型体系和纯固化基质块中的反应时间。这些条件可应用于复合复合材料，从中可回收原始碳纤维。
