Recycling of High-Value-Added Aramid Nanofibers from Waste Aramid Resources via a Feasible and Cost-Effective Approach.

High-performance aramid fibers are extensively applied in the civil and military fields. A great deal of waste aramid resources originating from the manufacturing process, spare parts, or end of life cycle are wrongly disposed (i.e., landfill, smash, fibrillation), causing a waste of valuable resources as well as severe environmental pollution. Although aramid nanofibers (ANFs) have recently been recently reported as one of the most promising building blocks due to their excellent properties, they suffer from an extremely high production expenditure, thereby greatly hindering their scale-up application. Herein, in this paper, from a resources-saving and cost-reductional perspective, we present a feasible top-down approach to recycle high value-added ANFs with an affordable cost from various waste aramid resources. The results indicate that although the reclaimed ANFs have a molecular weight reduction of 8.1% compared with the recycled aramid fibers, they still exhibit a molecular weight of 43.0 kg·mol-1 that represents the highest value compared to other methods. It is noteworthy that the fabrication cost of ANFs is significantly reduced (∼7 times) due to the reclamation of waste aramid fibers instead of the expensive virgin aramid fibers. The obtained ANFs show impressive tensile strength (149.2 MPa) and toughness (10.43 MJ·m-3), excellent thermal stabilities (Td of 542 °C), and a high specific surface area (65.2 m2·g-1), which endows them to be promising candidates for constructing advanced materials. Compared to the aramid pulp obtained by the traditional recycling method, ANFs show significant advantages in dimensional homogeneity, aspect ratio, dispersibility, film-forming property, and especially the excellent properties of the ANF film. In addition, the scale-up preparation of ANFs from the recycled waste aramid fibers is carried out, demonstrating it is highly economically viable. Therefore, this work provides a highly feasible and cost-effective recycle system to reclaim the waste aramid resources together with significantly reducing the preparation cost of ANFs.