Chemically\nRecyclable, Reprocessable, and Mechanically\nRobust Reversible Cross-Linked Polyurea Plastics for Fully Recyclable\nAramid Fiber Reinforced Composites

Aramid fiber reinforced composites (AFRCs) have received\nincreasing\nattention because of their excellent comprehensive performance including\nhigh mechanical strength, high modulus, and light weight. However,\nfull recycling of AFs from ARCFs is difficult to achieve. Herein,\nfully recyclable ARCFs are fabricated using reversible cross-linked\npolyurea plastics (PUHA) as the matrix. PUHA plastics are fabricated\nby cross-linking linear polyurea using hemiaminal groups. By changing\nthe main chain structures, two types of PUHA plastics are prepared\nwith excellent mechanical performance, which is comparable to that\nof traditional engineering plastics. PUHA plastics can be reprocessed\nat least five times without losing their original mechanical properties\nbecause of the dynamic exchangeability of the hemiaminal groups. Meanwhile,\nPUHA plastics can be rapidly depolymerized into linear polyurea under\nacidic conditions. When PUHA plastics are used as a matrix to fabricate\nAFRCs, the AFRCs exhibit excellent mechanical strength. Moreover,\ndue to the simple chemical recycling ability of PUHA plastics, AFRCs\ncan be fully decomposed into intact AFs and linear polyurea with high\npurity. This work presents the use of reversible cross-linked polyurea\nplastics in the fabrication of fully recyclable AFRCs and provides\nthe future direction of developing fully recyclable and high-performance\nfiber-reinforced composites.