Carbon fiber from natural biopolymer Bombyx mori silk fibroin with iodine treatment

Abstract

Carbon fibers were prepared from silk fibers after an iodine treatment and the carbon yield, fiber morphology, structure and mechanical properties were investigated.A single or multi step carbonization process was used for the preparation. In the single step process, silk fibroin (SF) fibers were heated from 25 to 800 °C with a heating rate of 5 °C min-1 under Ar atmosphere. However, the carbon fiber obtained was partially melted and was too fragile to handle. For better performance, SF fibers were treated with iodine vapor at 100 °C for 12 h and untreated and iodinated SF fibers were heated from 25 to 800 °C by a multi step carbonization process, which was defined based on the optimum thermal degradation rate of silk. In this multi step process, the carbon fibers obtained from iodinated SF were structurally intact and stable in appearance, and the carbon yield achieved was ca. 36 wt%, much higher than the value for untreated SF.X-ray diffraction, Raman spectroscopy and transmission electron microscopic observation revealed that the obtained carbon fibers from both untreated and iodinated SF were a basically amorphous structure. The strength of carbon fibers prepared from 1 iodinated SF using the multi step carbonization was considerably increased compared to that of untreated SF. According to viscoelastic measurement, by heating above 280 °C the iodine introduced intermolecular cross-linking of the SF, and its melt flow was inhibited which produced a higher yield and better performance of the carbon fiber.

Fabrication of high strength PVA/SWCNT composite fibers by gel spinning

“…Figure 1 shows Raman spectrum of pristine SWCNTs. The bands were observed at 1341 cm -1 (D band) and 1592 cm -1 (G band), corresponding to amorphous carbon impurities and carbon nanotubes, respectively [17]. The band intensity at 1341 cm -1 was extremely low, while the G-band had much higher intensity.…”

Thermal, chemical and morphological properties of carbon fibres derived from chemically pre-treated wool fibres

“…19,20 The use of iodine treatment to increase the carbon yield has also been extended to biobased precursors, such as silk broin. 21 In other work, sulphuric acid treatment of cellulosic bre has been shown to increase the carbon yield by 300%.…”

Molecular iodine/polymer complexes

“…Under identical conditions and in the same line of investigation as in [116], Kahn et al [118] studied the carbon formation from Antheraea pernyi silk fibroin fiber. The composition of the latter silk is different from that of B. mori silk, having predominantly alanine (Ala), aspartic acid (Asp), and arginine (Arg) amino acid residues.…”

“…Shao and his coworkers [115] treated a degummed and UV/ozone irradiated B. mori silk fiber with saturated iodine ethanolic solution in the dark at 22°C for 24 h. The content of iodine was about 5% in the bulk iodinated silk and 0.9% on the surface. Khan et al [116] reported a process of making carbon fiber from B. mori silk fibroin after iodine treatment. The silk fibroin was exposed to iodine vapors at 100°C for varying periods of time, after which the fiber color turned to dark brown.…”