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High mechanical performance materials at high temperature are highly desired for the materials used in high temperature industries. This study reports the aligned electrospun polyimide nanofiber belt (A-PI-NFB) fabricated from the electrospinning followed with imidization. The A-PI-NFB showed increased mechanical and thermal mechanical properties as increasing the imidization temperature. At room temperature, the A-PI-NFB imidized at 450 °C (A-PI-NFB-450) had the highest tensile strength (689 MPa) and E modulus (13.2 GPa). The thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA) showed that A-PI-NFB-450 possessed 80% tensile strength and 90% modulus when heated at 300 and 350 °C in N 2 , respectively. These excellent properties made A-PI-NFB good candidates for use in high temperature filtration, protective clothes etc. [ABSTRACT FROM AUTHOR]

Abstract: Copolymers, poly(acrylonitrile-co-monobutylitaconate-co-n-butylacrylate) (copolyacrylonitrile, co-PANs) with different content of monobutyl itaconate (MBI) were synthesized by free radical polymerization and then electrospun into aligned nanofibers. After thermal treatments of stabilization, carbonization, and graphitization, the resulting aligned co-PAN nanofibers were converted to aligned electrospun carbon nanofiber bundles (ECNFB) with diameters of approximately 200nm. FT-IR technique was applied to investigate the stabilization process of co-PAN nanofibers, while XRD, TEM and tensile tester were used to characterize the microstructures and mechanical properties of the ECNFB. The measured results revealed that MBI was a fairly useful comonomer for preparing high performance PAN-based CNFs by improving the stabilization of co-PAN nanofibers and by promoting the formation of ordered graphite crystals in the ECNFB. When the content of MBI unit in co-PAN was 5wt%, the aligned ECNFB exhibited a tensile strength of up to 1.8GPa and a Young׳s modulus of up to 97.0GPa, which is 86% and 67% higher than those of the ECNFB previously reported in our group respectively. [Copyright &y& Elsevier]

Mechanical properties of polyimide (PI) electrospun nanofibers could be improved by increasing imidization temperatures. However, the intrinsic mechanism on this phenomenon is highly required, which is helpful to improve mechanical properties of electrospun nanofibers by external thermal treatment. In this work, single electrospun PI nanofibers (SNF-PI) with different imidization temperatures were prepared. The nanofiber morphology was studied by SEM and AFM and the mechanical properties were measured by single fiber micro-tensile test. Polarized Raman Spectroscopy was applied to determine the PI molecular orientation in SNF-PI. The molecular orientation factor provides directly explanation on the effect of imidization temperatures on the mechanical properties of SNF-PI. [ABSTRACT FROM AUTHOR]