High-tenacity and high-modulus polyimide fibers containing benzimidazole and pyrimidine units

摘要

Polyimide fibers (PI) combine high thermal stability, good chemical and UV resistance. However, most commercial PI fibers including P84 (R), Kermel (R), Yilun (R) and Suplon (R) do not exhibit sufficiently high mechanical properties. Finding an appropriate method that is commercially available to prepare PI fibers with a high tenacity and modulus is required urgently for making large scale manufacturing attractive. Herein, we describe an approach to preparing high-performance PI fibers by introducing the heterocyclic pyrimidine and benzimidazole units into PI backbones. PI fibers prepared by this way exhibited a higher tenacity and modulus compared to those previously reported PIs and even Kevlar 49 (R) fibers due to the high molecular weight, strong hydrogen bonding interaction and highly oriented crystalline structure. In addition, the detailed structural analysis based on WAXD and SAXS has revealed that the stress-induced crystallization and more compact morphology formed in PI fibers by the post hot-drawing process. Accordingly, as the drawing ratio was set to 3.8, an optimum tenacity and modulus of the PI fiber reached to 2.3N/tex and 71.8N/tex, respectively, indicating that the resultant fibers have a great potential application as the reinforcing fiber in advanced composites.