• Pierlot, Tony
• Hillbrick, Linda
• Wong, Sherman
• Kaur, Jasjeet

Abstract

The performance of carbon fibers depends on the properties of the precursor polyacrylonitrile (PAN) fibers. Stretching of PAN fibers results in improved tensile properties, while potentially reducing its compressive properties.To determine optimization trade-offs, the effect of coagu-lation conditions and the stretching process on the compressive modulus in the transverse direc-tion (ET) was investigated. A method for accurately determining ET from polymer fibers with non-circular cross-sectional shapes is presented. X-ray diffraction was used to measure the crys-tallite size, crystallinity, and crystallite orientation of the fibers. ET was found to increase with decreasing crystallite orientation along the drawing direction, which decreases the tensile (EL) proportionally to crystallite orientation. Stretching resulted in greater orientation for fibers formed under the same coagulation conditions. Increasing the solvent concentration in the co-agulation bath resulted in a higher average orientation but reduced the impact of stretching on the orientation. The relationship between ET and EL observed in the precursor PAN fiber is retained after carbonization, with a 20% increase in ET achieved for a 2% decrease in EL. This indicates that controlled stretching of PAN fiber allows for highly efficient trading off of EL for ET in carbon fiber.

Topics

• impedance spectroscopy
• polymer
• Carbon
• x-ray diffraction
• drawing
• crystallinity
• wet spinning