The effect of the spinning conditions on the structure of mesophase pitch-based carbon fibers by Taguchi method

Abstract

Taguchi's experimental design was employed in the melt spinning of molten mesophase pitch to produce carbon fibers. The textures of the obtained carbon fibers were radial with varied crack angles, as observed by scanning electron microscopy and polarized optical imaging. The diameter, crack angle, preferred orientation, and tensile modulus of the produced samples were examined to investigate the influence of four spinning variables. The relative importance of the variables has been emphasized for each characteristic. The results show that thicker carbon fiber can be obtained with a smaller entry angle, a higher spinning temperature, a reduced winding speed, and an increased extrusion pressure. The winding speed was found to be the most significant factor in relation to the fiber diameter. While it was observed that thicker carbon fiber generally shows improved preferred orientation, the most important variable affecting the preferred orientation was found to be the entry angle. As the entry angle decreased from 120° to 60°, the shear flow was enhanced to induce more ordered radial alignment of crystallite planes so as to obtain carbon fibers with a higher degree of preferred orientation. As a consequence, the crack angle was increased, and the tensile modulus was improved.

Copper and Nickel Coating of Carbon Fiber for Thermally and Electrically Conductive Fiber Reinforced Composites

“…Another pathway to increase the thermal conductivity is the use of pitch-based carbon fibers, also called graphite fibers. The morphology of these fibers fundamentally differs from those of the commonly used carbon fibers based on polyacrylonitrile (PAN) [18,19,20].…”

Preparation and evaluation of isotropic and mesophase pitch-based carbon fibers using the pelletizing and continuous spinning process

“…The pitches are derived from coal tar or petroleum through thermal treatment and are classified as isotropic pitch (IP) or mesophase pitch (MP) based on their crystal structure. Anisotropic MP-based carbon fibers are used in higher value-added industries such as aerospace and expensive sporting goods [7–10] due to their higher tensile strength and electrical properties, whereas IP-based carbon fibers are used in other industries. The most popular method to prepare pitch-based carbon fibers is to spin the pitch fibers using a batch extruder composed of a cylindrical apparatus.…”

Impact of Spinning Conditions on the Structure and Tensile Properties of Mesophase Pitch Carbon Fibers

“…The structure of the fiber is largely developed during the spinning process, whilst post-treatments are employed to refine and perfect it (12). The stabilization is the least efficient and most time consuming part of the production (1).…”

“…A high modulus, high conductivity mesophase pitch carbon fiber is mainly a result from a high degree of preferred orientation of mesophase parallel to the fiber axis. The structure is largely developed during the fiber spinning process, while post-treatments are employed to refine and perfect the as-spun fibers (12). Thus, it is of critical importance to understand the mechanism of flow occurring in spinning step in order to strictly control the extrusion parameters to form thinner and highly ordered fibers.…”

“…Figure 2.13 shows the effect of the DDR in the tensile stress in a melt spinning experiment performed in a comercial liquid crystalline polymer. Jiang et al (12) employed DoE to observe the influence of simultaneous modification of process parameters in fiber's final diameter and degree of orientation. Higher spinning temperature, reduced winding speed and increased extrusion pressure were found to produce thicker carbon fibers with improved preferred orientation.…”