Abstract
Carbon fibers, which act as reinforcements in many applications, are often obtained from polyacrylonitrile (PAN). However, their production is expensive and results in waste problems. Therefore, we focused on producing carbon fibers from lyocell, a cellulose-based material, and analyzed the effects of the process parameters on their mechanical properties and carbon yields. Lyocell was initially grafted with polyacrylamide (PAM) via electron-beam irradiation (EBI) and was subsequently stabilized and carbonized. Thermal analysis showed that PAM grafting increased the carbon yields to 20% at 1000 °C when compared to that of raw lyocell, which degraded completely at about 600 °C. Stabilization further increased this yield to 55%. The morphology of the produced carbon fibers was highly dependent on PAM concentration, with fibers obtained at concentrations ≤0.5 wt.% exhibiting clear, rigid, and round cross-sections with smooth surfaces, whereas fibers obtained from 2 and 4 wt.% showed peeling surfaces and attachment between individual fibers due to high viscosity of PAM. These features affected the mechanical properties of the fibers. In this study, carbon fibers of the highest tensile strength (1.39 GPa) were produced with 0.5 wt.% PAM, thereby establishing the feasibility of using EBI-induced PAM grafting on lyocell fabrics to produce high-performance carbon fibers with good yields.
Highlights
Carbon fibers are widely used as reinforcement materials in the advanced composites for application in wind-turbine blades, high-tech aerospace devices, and high-quality sporting goods [1,2,3,4,5,6]
The spectrum of lyocell grafted with PAM peaks could be noted at 3323, 3196, 1653 cm−1, and 1604 cm−1; the intensity of these peaks, which are attributed to the -CONH2 group, increased with an increase in the PAM concentration
Grafting of Lyocell Fabrics with PAM via electron-beam irradiation (EBI) and Their Thermal Stabilization and Carbonization As illustrated in Figure 7, lyocell fabrics (10 × 10 cm2) were immersed in a solution of PAM (0.05, 0.1, 0.5, 1, 2, and 4 wt.%) dissolved in water, and they were irradiated with EBI of various dosages (100, 200, and 300 kGy); in our analysis, we observed that the effect of PAM concentration was higher than that of the EBI dose on the properties of carbon fibers
Summary
Carbon fibers are widely used as reinforcement materials in the advanced composites for application in wind-turbine blades, high-tech aerospace devices, and high-quality sporting goods [1,2,3,4,5,6]. An environmentally friendly and inexpensive precursor is required to develop high-performance carbon fibers. The tensile strength and yield of carbon fibers developed from this precursor tend to be low [19,20] Despite these disadvantages, cellulose-based carbon fibers should be considered instead of PAN-based carbon fibers as they offer advantages of an abundant supply of raw materials, and economic and environmental profit. There is much interest in developing cellulose-based carbon fibers with good mechanical properties and high yields. Similar to rayon-based fibers, lyocell fibers require pretreatment to enhance carbon yield and mechanical properties before thermal stabilization [27,28]. Further studies are required on lyocell-based carbon fibers to improve their mechanical properties and performance
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