Valorization of Waste Aramid Fibers: A Comparative Review of Deprotonation, Depolymerization, and Beyond

The extensive use of aramid fibers in high-performance sectors such as aerospace, defense, rail transportation, and personal protection has driven the continuous expansion of global production capacity, leading to rapidly growing volumes of waste aramid resources. However, recycling remains challenging due to the fibers’ persistently rigid molecular chains, aromatic polyamide structures, high crystallinity, and orientation, which confer resistance to mechanical processing and common chemical agents. This review systematically summarizes recycling technologies for aramid fibers—including deprotonation, depolymerization, pyrolysis, and mechanical method while evaluating their development trajectories. Notably, depolymerization achieves >90% monomer recovery, whereas solvent-free mechanical and deprotonation routes significantly enhance recycling efficiency and reduce carbon emissions compared to pyrolysis. Critical barriers to scalable implementation are identified, such as inefficient fiber-matrix interfacial separation, chemical reagent toxicity risks, and regulatory gaps in recycled product certification. By mapping pathways toward closed-loop utilization, this work provides foundational insights for advancing circularity of aramid fibers in the polymer industry.