A facile method to enhance UV stability of PBIA fibers with intense fluorescence emission by forming complex with hydrogen chloride on the fibers surface

To date, the main method in improving UV stability of aramid fibers is to coat ultraviolet screening agent on the surface of fibers. However, this method has a disadvantage that the coating tends to fall off when the fibers are exposed to an external force. In the present research, A diamine monomer 2-(4-aminophenyl)-5-aminobenzimidazole (PABZ) was introduced to modify poly (p-phenylene terephthalamide) by copolymerization, and corresponding modified aramid fibers (PBIA fibers) were prepared. we found that PBIA fibers can form complex with hydrogen chloride (HCl) which would not lead to the obvious decrease in mechanical properties, and the decomplexation of HCl can only be achieved at high temperature (higher than 280 °C). At the same time, PBIA/HCl complex molecule showed intense fluorescence emission, and which can provide an effective way to dissipate the harmful UV energy, thus, the UV resistance of PBIA fibers can be improved. In addition, the HCl have the ability to quench the photoactive triplet state of PBIA fibers, which can also contribute to improve the UV resistance of PBIA fibers. After 48 h UV irradiation, the PBIA/HCl complex fibers almost remained their tensile performances (only about 3% loss in tensile strength), and UV irradiation did not bring the obvious deterioration in structure and performance of the complex fibers. On the contrary, for PBIA fibers, its chemical structure and physical properties all suffered to obvious damages (about 15% loss in tensile strength). The UV resistance of PBIA/HCl complex fibers is approximately 5 times higher than that of PBIA fibers.