In this study, using three types of resins (each with unique material properties) as a matrix, and carbon black (CB) as a conductive additive, conductive fibres were fabricated through a melt-spinning process. An examination of the electrical conductivity revealed that a CB/polyethylene terephthalate (PET) composite had a low percolation value of 0.58 wt%, and thus the highest conductivity of the three resin types. These results indicate that CB/PET fibres could be used to manufacture antistatic fabrics.

To overcome the disadvantages of discontinuous conventional batch extruders, a continuous screw extruder is introduced to manufacture pitch-based carbon fibers. For a carbon fiber preparation process, an oxidation time of 8 h was determined to be optimal for obtaining desirable mechanical properties of the fibers acquiring employing the screw extruder. It is hypothesized that the differences in the properties of the carbon fibers fabricated utilizing the batch and screw extruders originate from the melt spinning time; therefore, a combined equation for the total amount of heat treatment from the pitch precursor through the oxidation process is established in this study. The crystallinity of the carbon fibers is confirmed to correspond to the differences in mechanical properties as the oxidation time increases. The poor mechanical properties of the carbon fibers that are insufficiently oxidized are a result of irregular oxidation from the sheath to the core of the fiber cross section. However, the over-oxidized carbon fibers also show poor mechanical properties than the optimal fibers. This result further affirms that excessive oxidation times cause unstable chemical bonding, which interrupts the formation of stable crystal structures after carbonization.

Collagen is a protein that is a major component of animal skins and tendons. It is used in various medical, cosmetic, and food products through extraction and purification. The fibrous products of purified collagen fibers extracted from raw mammal materials have relatively excellent mechanical properties and are used for high-end medical products. In this study, we examined collagen materials produced from porcine and fish skins, which are major sources of collagen raw materials. We examined a method for spinning collagen fibers from fish skin-based collagen and analyzed the physical properties of those collagen fibers. In addition, we examined the characteristics and advantages of conjugated fibers according to their porcine- and/or fish skin-based compositions. The spinnability and mechanical properties of these conjugated fibers were analyzed according to their compositions. The mechanical properties of collagen structure are determined by hydroxyproline content and can be manipulated by the composition of collagen in the conjugated fibers.

Although polyacrylonitrile (PAN)-based carbon fibers have been successfully commercialized owing to their excellent material properties, their actual mechanical performance is still much lower than the theoretical values. Meanwhile, there is a growing demand for the use of superior carbon fibers. As such, many studies have been conducted to improve the mechanical performance of carbon fibers. Among the various approaches, designing a strong precursor fiber with a well-developed microstructure and morphology can constitute the most effective strategy to achieve superior performance. In this review, the efforts used to modulate materials, processing, and additives to deliver strong precursor fibers were thoroughly investigated. Our work demonstrates that the design of materials and processes is a fruitful pathway for the enhancement of the mechanical performance of carbon fibers.

Highly electrical conductive fibers have received significant attention because of their potential to be utilized for wearable technology. Conductive fibers have already been developed by many research groups using metal and carbon nanotubes (CNT); however, productivity is limited. Conductive fibers composed of conductive additives embedded in a polymer matrix were fabricated by a melt-spinning process. This enables the scaling-up of production and gives high mechanical strength compared to fibers prepared by other processes. Silver (Ag) was selected for the conductive material, and embedded in polypropylene (PP) fiber. However, the melt-spinning process has an inherently lower filler content threshold; therefore, it was difficult to fabricate with sufficient silver for the required electrical properties. CNT forests were introduced to make up for this shortcoming, and they could serve as a conductive bridge between unconnected Ag. The CNT percolation effect confirmed that non-conductive Ag/PP increases electrical conductivity after CNTs were added. It was determined that 80 nm Ag (46 wt%) and single wall CNT (4 wt%) embedded PP composite fiber (Ag80/SW_46/4) was the optimum fiber; with a thickness of less than 100 µm its electrical conductivity was 4.1–7.2 × 10⁻² S/cm. Conductive fabric was fabricated using our composite fiber, and it had higher electrical conductivity than that of a single fiber because multi-filaments induced lower electrical resistance. Although the electrical value attained does not approach a satisfactory goal, it is thought that this fiber has a potential to be applicable for wearable technology.

Polyacrylonitrile (PAN) fibers are typically used as precursor fibers for carbon fiber production, produced through wet-spinning processes. The drawing process of the spun fiber can be classified into dry and wet drawing processes. It is known that the drawing stability and stretching ratio differ depending on the drawing process; however, the elementary characteristics are approximately similar. In this study, the mechanical properties of PAN fibers have been examined based on these two drawing processes with the differences analyzed through the analysis of microstructures. Further, to examine the composition of the fiber, element analysis has been conducted, and thereafter, the microstructure of the fiber is examined through X-ray diffraction analysis. Finally, the characteristics of PAN fibers and its mechanical properties has been examined according to each drawing condition. There are differences in moisture content and microstructure according to the drawing process, and it affects the tensile behavior. The results obtained could have potential implications if the processes are combined, as it could result in a design for a stable and highly efficient drawing process.