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Electrospun polyimide (PI) nanofiber nonwovens with excellent mechanical and thermal performance are highly required in many applications. The addition of phosphorus-containing compounds could be used as plasticizer to achieve this purpose. Herein, different amounts of trace diphenyl phosphate (DPhP) as plasticizer are added into the PI's precursor for electrospinning. After imidization, phosphorous-containing electrospun PI nonwovens (PI-PX) are produced. The results indicate that the addition of DPhP significantly enhanced the thermal and mechanical properties of PI-PX. PI-P0.6 (0.6 wt% DPhP) shows a T5% of 510 °C in air and 561 °C in Ar, 29 °C and 40 °C higher than those of pure PI. PI-P0.6 also shows the highest tensile strength/modulus/toughness of 44 MPa/2.0 GPa/8.5 MPa, 208 MPa/9.7 GPa/40.7 MPa, and 123 MPa/3.3 GPa/25.1 MPa, respectively, when applying different thickness determinations. In addition, PI-P0.6 also exhibited much higher puncture strength than other Li-ion battery separators. Such PI-PX composite nonwovens would be good candidates for various applications, especially for Li-ion battery separators. [ABSTRACT FROM AUTHOR]

High mechanical performance carbon nanofibers are highly required for the carbon nanofiber-reinforced composites, and it is necessary to develop novel precursors for the preparation of carbon nanofibers. In this work, blends of poly(acrylonitrile-butyl acrylate mono-butyl itaconate) (co-PAN) and polyamic acid (PAA) were electrospun into aligned nanofibers and the nanofibers were converted to carbon nanofibers by thermal imidization, pre-oxidation and high-temperature carbonization. FT-IR spectroscopy was applied to monitor the chemical structures of the nanofibers before and after pre-oxidation. Tensile tests were used to characterize the mechanical properties of electrospun carbon nanofibers (ECNFs). The microstructures of ECNFs were investigated by high-resolution TEM and Raman spectroscopy. The results indicated that the ECNFs derived from blend of co-PAN/PAA with molar ratio of 6/4 and with carbonization temperature of 1400 °C possessed the highest tensile strength of 1212 MPa, which could be attributed to the ordered graphitic structures in ECNFs. [ABSTRACT FROM AUTHOR]