A novel strategy of fabricating high performance UV-resistant aramid fibers with simultaneously improved surface activity, thermal and mechanical properties through building polydopamine and graphene oxide bi-layer coatings

Using facile strategy to prepare UV resistant aramid fibers (KFs) with high surface activity, thermal and mechanical properties is the most important and urgent issue of sustainably developing high performance organic fibers. Herein, a novel two-step strategy has been built to prepare new KF (KF-PDA-GO) with remarkably improved integrated performances by forming polydopamine (PDA) and graphene oxide (GO) bi-layer coatings on the surfaces of KFs. Orthogonal tests based on three factors and three levels were designed and carried out to systematically study the influences of dopamine (DA) concentration, GO concentration and reaction temperature on the structure and performances of KF-PDA-GO fibers. Results show that the reaction temperature is the decisive factor for both surface active and UV-resistance. All KF-PDA-GO fibers not only have greatly improved surface activity and UV resistance, overcoming the two intractable disadvantages of KFs, but also show outstanding thermal resistance and higher tensile properties including tensile strength, modulus, elongation and break energy. For the new fiber (KF-PDA-GO3) prepared with the optimum conditions, its surface free energy increases 54%, meanwhile the retention of tensile strength after 168 h-UV irradiation is as high as 93.4%, almost the best value among the latest modified KF fibers reported. Different failure modes are found between original and modified KF fibers through intensively discussing the morphological and chemical structures of fibers. This investigation provides a novel and facile method to develop new KF fibers with higher integrated performances, especially outstanding surface activity, UV resistance, thermal and mechanical properties.